the role of smell and mouthfeel cues on fat perception and

The role of smell and mouthfeel cues on fat perception and preference

in dairy food products

MSc thesis

Irene Schiprowski

Irene Schiprowski The role of smell and mouthfeel cues on fat perception and preference in dairy food products

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The role of smell and mouthfeel cues on fat perception and preference in dairy food products

MSc thesis of Irene Schiprowski

Student number: 960203740080 Master programme: Food Technology

Specialisation: Sensory Science

Chair group: Food Quality and Design Course code: FQD-80436

Supervisor: Dieuwerke Bolhuis Examiner: Vincenzo Fogliano

Wageningen University & Research

March 2020


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Abstract

A higher preference for fat rich foods is a major risk factor for obesity. High fat foods are passively overconsumed due to their weak effect on satiety and their high energy density. Therefore, it is important to better understand fat perception and preference in food products. Until now, the relative contribution of sensory modalities on the perception and preference of fat remained unclear. In this study, the role of smell and mouthfeel cues on fat perception and preference in low and high viscous dairy food products was examined. Viscosity and tribology were measured to investigate whether fat perception and preference were based on thickness and/or friction of the food products. Fifty participants evaluated fat perception and preference in low and high viscous food products (respectively milk and quark) with four different fat contents (1.5%, 3.0%, 4.5% and 6.0%). They were asked to rank the samples according to fat level and in order of preference. Ranking was done under four different sensory conditions: orthonasal smell, retronasal smell, mouthfeel, and both smell and mouthfeel. Results demonstrated that participants were able to discriminate the different fat contents by orthonasal smell only, by mouthfeel only and by combining smell and mouthfeel in both low and high viscous food products. When only retronasal smell cues were available, fat discrimination seemed to be more difficult. Fat discrimination seemed to be easier in low viscous foods compared to high viscous foods. The preference data did not show clear preference for any of the fat contents in milk evaluated with different sensory cues. For quark, the highest fat content sample (6.0% fat quark) was significantly more preferred in the mouthfeel condition. Milk with a fat content of 6.0% showed a significantly higher viscosity compared to other milk samples. Viscosity of the quark samples did not show any significant differences. Friction differed between fat levels for both milk and quark samples. Findings of the fat perception and preference tests seem to be explained by the tribological properties of the food products used in this study. In conclusion, fat discrimination seems to be more difficult when only retronasal smell cues are available. Although humans are able to discriminate fat by orthonasal smell and mouthfeel, fat discrimination ability is not increased when both smell and mouthfeel cues are present.


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Contents

Abstract ............................................................................................................................................. 3

1 Introduction .................................................................................................................................... 6

2 Materials and methods ................................................................................................................... 8

2.1 Experimental design ................................................................................................................. 8

2.2 Participants ............................................................................................................................ 10

2.3 Test foods .............................................................................................................................. 10

2.4 Instrumental measurements .................................................................................................. 11 2.4.1 Viscosity measurements.................................................................................................. 11 2.4.2 Tribology measurements ................................................................................................. 11

2.5 Data analyses ......................................................................................................................... 11 2.5.1 Instrumental data analysis .............................................................................................. 11 2.5.2 Perception data analysis ................................................................................................. 12 2.5.3 Preference data analysis ................................................................................................. 13

3 Results .......................................................................................................................................... 13

3.1 Instrumental measurements results ....................................................................................... 13 3.1.1 Viscosity results .............................................................................................................. 13 3.1.2 Tribology results ............................................................................................................. 15

3.2 Fat perception test results...................................................................................................... 16

3.3 Fat preference test results ..................................................................................................... 18

4 Discussion ..................................................................................................................................... 21

4.1 Insights from the fat perception test ...................................................................................... 21

4.2 Insights from the fat preference test ...................................................................................... 22

4.3 Recommendations ................................................................................................................. 22

5 Conclusion .................................................................................................................................... 23

Acknowledgements .......................................................................................................................... 24

References ....................................................................................................................................... 25

Appendices ...................................................................................................................................... 27

Appendix 1: Example questionnaires............................................................................................ 27 Appendix 1.1: Example questionnaire fat preference ............................................................... 27 Appendix 1.2: Example questionnaire fat perception ............................................................... 30

Appendix 2: Results of the instrumental data analysis .................................................................. 33 Appendix 2.1: SPSS output of the independent samples t-test to compare viscosity of milk and quark samples ......................................................................................................................... 33 Appendix 2.2: SPSS output of the one-way ANOVA’s with Tukey’s post hoc tests to compare viscosity of milk and quark samples regarding fat level ............................................................ 33


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Appendix 3: Results of the perception data analysis ..................................................................... 35 Appendix 3.1: SPSS output of the tests of normality for the discrimination scores of milk and quark under four different sensory conditions ......................................................................... 35 Appendix 3.2: SPSS output of the one sample Wilcoxon signed-rank tests against zero ............ 36 Appendix 3.3: SPSS output of the Wilcoxon signed-rank test to compare discrimination ability scores between milk and quark ............................................................................................... 36 Appendix 3.4: SPSS output of the Wilcoxon signed-rank tests to compare discrimination ability scores between milk and quark under four different sensory conditions .................................. 37 Appendix 3.5: SPSS output of the Friedman ANOVA’s to compare discrimination ability scores between four different sensory conditions for milk and quark ................................................. 37 Appendix 3.6: SPSS output of the pairwise comparisons of the discrimination ability scores by Wilcoxon signed-rank tests under four different sensory conditions for milk and quark ........... 37 Appendix 3.7: SPSS output of the Friedman ANOVA’s of the perception ranking scores per sensory condition for milk and quark ....................................................................................... 38 Appendix 3.8: SPSS output of the pairwise comparisons of the perception ranking scores of four fat levels by Wilcoxon signed-rank tests under the orthonasal smell condition, the mouthfeel condition and the smell + mouthfeel condition for milk and quark ........................................... 39

Appendix 4: Results of the preference data analysis ..................................................................... 41 Appendix 4.1: SPSS output of the Friedman ANOVA’s of the preference ranking scores per sensory condition for milk and quark ....................................................................................... 41 Appendix 4.2: SPSS output of the pairwise comparisons of the preference ranking scores of four fat levels by Wilcoxon signed-rank tests under the retronasal smell condition for quark .......... 42 Appendix 4.3: SPSS output of the Friedman ANOVA’s to compare preference ranking scores between four different sensory conditions for milk and quark ................................................. 42 Appendix 4.4: SPSS output of the Wilcoxon signed-rank tests to compare preference ranking scores between milk and quark under four different sensory conditions .................................. 42 Appendix 4.5: Results of the binomial tests of the number of times a sample was most preferred under four different sensory conditions for milk and quark...................................................... 43 Appendix 4.6: Results of the chi-square tests to compare the number of times a sample was most preferred between four different sensory conditions for milk and quark ......................... 44


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1 Introduction

A higher liking for fat is a major risk factor for obesity (Lampuré et al., 2016). This can be explained by results of earlier studies showing that foods high in dietary fat are passively overconsumed due to their weak effect on satiety and their high energy density (Bell & Rolls, 2001; Blundell, Burley, Cotton, & Lawton, 1993; Blundell & MacDiarmid, 1997; Green, Burley, & Blundell, 1994; Green, Wales, Lawton, & Blundell, 2000; Miller, Castellanos, Shide, Peters, & Rolls, 1998). Besides, it is known that sugar and salt have a larger impact on food liking than fat and thereby promote passive overconsumption of fat (Bolhuis, Costanzo, & Keast, 2018; Bolhuis, Costanzo, Newman, & Keast, 2015). One way to combat overconsumption is to reduce the fat content in food products. However, the problem is that foods that are high in fat are usually more palatable than many low fat foods (Drewnowski, 1998). Therefore, it needs to be investigated how humans perceive fat in foods in order to help food product development to design foods with lower fat contents maintaining palatability.

It is known that dietary fat is unique in its way that it is perceived through a combination of olfactory (smell), somatosensory (mouthfeel) and gustatory (taste) sensations (Drewnowski, 1997; Schiffman, Graham, Sattely-Miller, & Warwick, 1998). Olfactory perception of fat occurs via orthonasal and retronasal perception. Orthonasal smell is associated with sniffing and refers to the smell of volatiles that reach the olfactory epithelium, located in the nasal cavity, via the nose, while retronasal smell is the smell of volatiles that reach the olfactory epithelium via the mouth (Boesveldt & Lundström, 2014). It has been demonstrated by Boesveldt & Lundström (2014) that humans are able to detect minute differences between milk samples with varying grades of fat via odours alone. As they only studied orthonasal smell of milk samples with a quite low viscosity, it remains unclear whether this is also valid for products with a higher viscosity, such as quark. Furthermore, multiple studies revealed that humans can discriminate vapor-phase fatty acids both via orthonasal and retronasal perception (Chukir, Darlington, & Halpern, 2013; Wajid & Halpern, 2012). Additionally, Bolton & Halpern (2010) showed that the orthonasal detection of oleic fatty acids is significantly different from the retronasal detection as participants made more correct responses for orthonasal than for retronasal smelling. However, for stearic and linoleic fatty acids, there were found no significant differences between numbers of orthonasal and retronasal correct responses. Therefore, further investigation on fat perception via both orthonasal and retronasal smell is needed to better understand the effect of odour on the overall fat perception of humans.

Another sensory modality contributing to fat perception is mouthfeel. It is known that humans are not able to perceive fat globules in a food product in the oral cavity individually, but they perceive them as creamy (Montmayeur & Le Coutre, 2009). Creaminess is associated with a pleasant sensation while consuming and a high quality of the food product (Akhtar, Stenzel, Murray, & Dickinson, 2005). The lubrication properties of fat can enhance creaminess as fat located at the surface of the oral food bolus provides lubrication between the bolus and the oral tissue with the sensory receptors, causing a fatty and creamy perception in the mouth (de Wijk & Prinz, 2005; de Wijk & Prinz, 2007). In this study, the lubrication properties of fat will be measured by tribology. Tribology includes the study of the principles of lubrication, friction and wear between surfaces in relative motion. These occur during motion of oral surfaces, such as the tongue, palate and teeth, and arise in the oral processing of food (Shewan, Pradal, & Stokes, 2020).

Furthermore, fat content has an influence on the mouthfeel of a product. A higher fat content causes a product to be perceived as thicker (Le Calvé et al., 2015). Besides, it is known that creaminess perception is enhanced by a higher viscosity of the product (Akhtar et al., 2005). For those reasons, a more viscous product gives the illusion of a higher fat content and therefore humans may discriminate fat in foods based on thickness (Montmayeur & Le Coutre, 2009). Furthermore, it is known that the fat discrimination ability of humans varies with the viscosity of a product. It seems to be more difficult to


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discriminate different fat levels in high viscous products compared to low viscous products (Drewnowski, Shrager, Lipsky, Stellar, & Greenwood, 1989; Le Calvé et al., 2015).

Besides smell and mouthfeel, taste also plays a role in fat perception. A study by Mattes (2008) demonstrated the ability of humans to detect short-, medium- and long-chain saturated fatty acids which may be mediated by the presence of receptors capable of binding an array of free fatty acids. However, taste seems to be a minor contributor to the overall fat perception as previous research showed that the detection threshold for oleic and linoleic acids was significantly higher for taste than for multimodal stimulation which included smell, taste and texture, meaning that it is more difficult to perceive fat only by taste (Chalé-Rush, Burgess, & Mattes, 2007). Therefore, taste is not examined as a separate sensory condition in this study. It is assumed that humans are not able to discriminate fat in foods based on taste only.

Another study assessed the role of smell, taste, flavour and texture cues on the identification of vegetables (van Stokkom, Blok, van Kooten, de Graaf, & Stieger, 2018). They found that identification and thereby the overall sensory perception was the highest when all sensory cues (smell, taste, flavour and texture) were available compared to only smell cues, only taste cues, or only smell and taste cues. Since it is unclear whether the same is true for fat perception, it would be interesting to further investigate this in fat containing foods such as milk and quark.

Earlier performed studies and theses examining fat perception made use of high fat food products with fat contents up till 20%. However, most viscous dairy food products contain up till about 6% fat. Therefore, this study will research fat perception by using dairy food products containing up till about 6% fat in order to provide realistic results. Additionally, fat preference will be investigated using the same dairy food products. Fat perception and preference will be examined in four different sensory conditions: orthonasal smell, retronasal smell, mouthfeel and both smell and mouthfeel. In order to examine if fat perception and preference are based on thickness and/or friction of a food product, viscosity and tribology of the dairy food products will be measured.

Based on previously described studies and results of earlier performed theses showing that fat is perceived through both smell and mouthfeel, it is hypothesised that fat perception and thereby the fat discrimination ability of humans will be enhanced if all sensory cues (both smell and mouthfeel) are available compared to if only orthonasal smell, only retronasal smell or only mouthfeel cues are available. It is also hypothesised that humans will prefer a higher fat level if only mouthfeel cues are present as recent research demonstrated that patients suffering from congenital smell loss, and thus perceiving foods by mouthfeel cues only, have a higher preference for fatty foods compared to healthy people who perceive foods by both smell and mouthfeel cues (Postma, De Graaf, & Boesveldt, 2020). A reason for this could be that fat perception is relatively more difficult when only mouthfeel cues are present compared to both smell and mouthfeel cues, leading to the need of a higher fat level in products to like them. Consequently, it is hypothesised that humans will prefer a lower fat level if all sensory cues are present as fat perception is thought to be better in this condition. Also the fact that fat perception consists of a combination of both smell and mouthfeel confirms this theory (Drewnowski, 1997; Schiffman et al., 1998).

Since current knowledge regarding the specific influence of the sensory cues on fat perception and preference is lacking, the following research question arises: In which way do sensory cues affect fat perception and preference in low and high viscous food products, and can these effects be explained by the rheological and/or tribological properties of the food products?


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2 Materials and methods

2.1 Experimental design In this study, participants evaluated fat perception and preference in low and high viscous food products (respectively milk and quark) with four different fat levels (1.5%, 3.0%, 4.5% and 6.0%). In order to prevent sensory fatigue, sensory evaluation was divided into two sessions. Fat preference was chosen to be tested in the first session and fat perception in the second session. In this way, participants were not biased before preference testing which means that they could spontaneously rank the samples in order of preference. The preference tests took place between the 18th and the 20th of November 2019 and the perception tests between the 2nd and the 4th of December 2019. Due to time constraints, three participants opted for coming in twice at the second testing week from the 2nd till the 4th of December with a minimum of one day between the testing sessions. All sensory tests took place in facilities of the Helix building on the campus of the Wageningen University.

To investigate fat preference, participants were asked to rank the four different samples in order of preference. To test fat perception, participants were asked to rank the four different samples according to fat level. During the perception test, a 0.0% fat content sample and a 10.0% fat content sample were provided as reference samples in order to decrease the risk of inverted ranking. Ranking was done under four different sensory conditions to investigate the individual and combined effect of smell and mouthfeel cues on fat perception and preference: orthonasal smell, retronasal smell, mouthfeel, and both smell and mouthfeel. In order to test orthonasal smell, participants were asked to smell the samples with their nose when closing their mouth. In the retronasal smell condition, participants were provided with a so called modified odour container which is a 150 ml container with a silicone lid (see figure 1). A straw was put in the lid through which the participants could inhale the volatiles inside the container. To prevent the volatiles from escaping the container, the straw was covered with an Eppendorf tube. An air vent was provided by another Eppendorf tube from which the bottom was cut off. Participants were asked to open the air vent, take off the tube from the straw and inhale once via the straw while wearing a nose clip. After this, participants were asked to remove their nose clip and exhale through their nose while keeping their mouth closed. To test mouthfeel, participants were asked to taste the samples while wearing their nose clip. Finally, both smell and mouthfeel were tested by asking participants to taste the samples in usual manner. Before the first session, participants were familiarised with the use of a nose clip and a modified odour container.

Figure 1: Modified odour container (150 ml) with lid, straw and air vent used to investigate retronasal smell.

Milk and quark as well as the different sensory conditions (orthonasal smell, retronasal smell, mouthfeel, and both smell and mouthfeel) were randomly assigned to each participant. Also the four different fat content samples followed a randomised order of presentation and were labelled with randomly chosen three-digit codes. Participants were provided with a paper survey on which they


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could fill in their ranking orders. An example questionnaire for both preference and perception tests can be found in respectively appendix 1.1 and 1.2. If required, participants were provided with a spoon, a modified odour container and/or a nose clip to prevent confusion about which sensory condition participants needed to perform. Figure 2 gives an overview of the study design of the research.

Figure 2: Overview of the study design entailing the sensory evaluation of milk and quark samples with four different fat levels under four different sensory conditions in two sessions. In the second session (fat perception), a 0.0% fat content sample and a 10.0% fat content sample were provided as reference samples.


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2.2 Participants Participants were recruited via an online Facebook platform for students in Wageningen, via Wageningen University e-mail and flyers were spread at different buildings on the campus of Wageningen University. Inclusion criteria were being familiar with milk and quark by means of consuming both milk and quark at least once a month, an age between 18 and 40 years, and a Body Mass Index (BMI) between 18.5 and 27.5 kg/m2 as it is known that age and BMI have an influence on taste perception (Doty, Chen, & Overend, 2017; Miller, Polgreen, Segre, & Polgreen, 2019). Exclusion criteria were smoking and pregnancy as it is known that these factors affect taste perception (Doty, Chen, & Overend, 2017; Nanou, Brandt, Weenen, & Olsen, 2016). Participants were also excluded when being lactose intolerance, having milk related allergies or having difficulties with eating or swallowing.

In total, 102 students applied from which 32 were excluded due to the inclusion and exclusion criteria listed above. Only 11 students of the 70 students left were male. Therefore, these students were excluded to get a more homogenous group of participants. Subsequently, 59 students were invited and asked to fill in their preferable time slots. Six students did not reply, leaving a total of 53 participants. Due to personal reasons, three participants dropped out during the first testing week. A total of 50 female participants (mean age 23.0 ± 2.8 years; mean BMI 21.8 ± 2.2 kg/m2; 20 Dutch participants; 14 other European participants; 16 non-European participants; 18 different nationalities) completed the study.

Participants were asked not to wear any scented products on the day of testing, nor to eat or drink anything other than water one hour prior to testing. Additionally, they were asked to eat the same breakfast (and lunch) on both testing days. To remind them about this, they received a reminder email one day prior to testing and at the end of the questionnaire participants were asked to fill in what they ate for breakfast (and lunch).

2.3 Test foods Low viscous and high viscous products (respectively milk and quark) with six different fat levels (0.0%, 1.5%, 3.0%, 4.5%, 6.0% and 10.0%) were prepared. For the milk samples, Albert Heijn (AH) cream (35% fat content) was added to AH skimmed milk (0.0% fat content) to reach the desirable fat contents. For the quark samples, AH skimmed quark (0.0% fat content) was mixed with AH cream (35% fat content). The corresponding recipes of the samples are shown in table 1. A basic hand whisk was used to mix the samples homogeneously after adding the cream to the milk or quark. However, by adding cream, the viscosity and colour of the samples changed a bit. As previous thesis experiments showed that adjusting the viscosity of the samples was highly labour-intensive and did not give the desired result, there was made no correction for these differences in viscosity. In order to mask the colour differences between the samples, red light was used in the sensory booths.

Table 1: Recipes of milk and quark samples with six different fat levels.

Fat content (% w/w)

Skimmed milk/ skimmed quark

(% w/w)

Cream (% w/w)

0.0 100.0 0.0 1.5 95.7 4.3 3.0 91.4 8.6 4.5 87.1 12.9 6.0 82.9 17.1

10.0 71.4 28.6


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The quark samples were prepared in batches of 1.75 kg on every testing day and stored in the refrigerator. If there was quark left at the end of the testing day, it was thoroughly mixed and re-used on the next day. The samples were served in 30 ml transparent plastic medicine cups and 150 ml modified odour containers. They were removed from the refrigerator 30 minutes prior to testing to warm up to room temperature. This was done as it was assumed that participants were able to smell the volatiles of the samples at room temperature.

The milk samples were prepared in batches according to the number of participants that would arrive every time slot. As the milk and cream mixture separated after 40 minutes, the milk samples were prepared 20 minutes before each time slot. Because the mixture separated again after 8.5 minutes when stirred after the first separation, the mixtures were stirred before they were poured in the cups during testing.

2.4 Instrumental measurements Some instrumental measurements were performed to define and understand the rheological and tribological properties of the 12 different milk and quark samples that were evaluated during the sensory test. The milk samples were prepared 20 minutes before measuring and thoroughly stirred directly before measuring. The quark samples were prepared in the morning, removed from the refrigerator 30 minutes before measuring and thoroughly stirred directly before measuring.

2.4.1 Viscosity measurements In order to determine the viscosity of both milk and quark samples, a rheometer (Anton Paar) was used. The measuring temperature was set to 20 °C. Viscosity was measured over a five minutes time interval and during this interval 30 measurements were performed, one measurement every ten seconds. The shear rate increased from 0.1 to 500 s-1. For the milk samples, a concentric cylinder measuring system with a volume of 4.7 ml was used as concentric cylinders are usually used for low viscous liquids (Fernanda, 2018). For the quark samples, a plate-plate measuring system with a diameter of 50 mm was used as plate-plate systems are commonly used to measure high viscous products (Fernanda, 2018). The gap size between the plates was set to 150 mm. Both milk and quark samples were measured in duplicate.

2.4.2 Tribology measurements A tribometer (Anton Paar) with a ball-on-three-pins set-up, consisting of a glass ball and three PDMS pins, was used for measuring friction of the samples. The measuring temperature was set to 20 °C and the normal force was set to 1 N. The friction factor was measured over a five minutes time interval and during this run 300 measurements were performed, one measurement per second. The sliding velocity increased from 1∙10-8 to 1 m/s. As the first run was not reliable because it got fluctuations, per sample two runs were performed from which the data of the first run was not used for data analysis. In between the two runs, a five minutes break was set up to give the sample some time to restructure. In total, the test took 15 minutes per sample. Also for tribology, both milk and quark samples were measured in duplicate.

2.5 Data analyses The data was analysed by SPSS Statistics, PQRS and Microsoft Excel. Significance was assumed at α=0.05.

2.5.1 Instrumental data analysis Microsoft Excel was used to calculate the mean viscosity values with corresponding standard deviations under increasing shear rate from 0.1 to 500 s-1 for each milk sample. For quark, mean viscosity values and standard deviations were calculated per sample at a shear rate of 50 s-1 as this is


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considered to be the standard oral shear rate (Ong, Steele, & Duizer, 2018). In order to see whether the viscosity of the milk and quark samples was significantly different from each other, an independent samples t-test was conducted in SPSS. In addition, a one-way analysis of variance (ANOVA) with Tukey’s post hoc test for pairwise comparison was performed to see whether the viscosity of the milk samples differed regarding fat level. Also to check the difference between the viscosity of the quark samples, a one-way ANOVA with Tukey’s post hoc test was used.

Mean friction factors and standard deviations of the duplicates were calculated by using Microsoft Excel. As it is unknown which sliding velocity value corresponds to the velocity in the mouth, it was not possible to calculate mean friction factor values under a certain sliding velocity and then perform statistical tests. Therefore, the Stribeck curves of the different samples were compared by visual inspection.

2.5.2 Perception data analysis In order to determine how well participants were able to rank the milk and quark samples in the correct order, discrimination scores were calculated (Rider, 1952). As the lowest fat content sample (1.5% fat content) was called 1 and the highest fat content sample (6.0% fat content) was called 4 in this case, the correct order participants needed to give was 1234. This resulted in a maximum score of 6. If the order was completely inverted, so 4321, a minimum score of -6 was achieved. In table 2 an example calculation for rank order 2314 is given. If a pair of samples was ranked in the correct order, the score was 1. If a pair of samples was ranked in the incorrect order, the score was -1. This resulted in a total score of 2 when participants gave rank order 2314. Table 2: Example calculation for rank order 2314.

Pair of samples

Correct order

Incorrect order

Score

23 1 +1 21 1 -1 24 1 +1 31 1 -1 34 1 +1 14 1 +1 Total score 4 2 2

In total, 24 different ranking orders were possible. An overview of all discrimination scores for these different ranking orders is given in table 3.

Table 3: Discrimination scores for all 24 different ranking orders. Ranking order

Score Ranking order

Score Ranking order

Score

1234 6 2314 2 3412 -2 1243 4 2341 0 3421 -4 1324 4 2413 0 4123 0 1342 2 2431 -2 4132 -2 1423 2 3124 2 4213 -2 1432 0 3142 0 4231 -4 2134 4 3214 0 4312 -4 2143 2 3241 -2 4321 -6


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After collecting all discrimination scores, a Shapiro-Wilk test was conducted to check if the data was normally distributed. Microsoft Excel was used to calculate the mean and standard deviation of the discrimination scores per sensory condition. SPSS was used to conduct a Wilcoxon signed-rank test per sensory condition for both milk and quark to test if the average discrimination scores were significantly different from zero, the average achievable score when participants ranked randomly. In addition, multiple Wilcoxon signed-rank tests were performed to test the effect of low and high viscous products (respectively milk and quark) on the fat discrimination ability. Friedman ANOVA’s were conducted to test the effect of sensory conditions on the fat discrimination ability. Pairwise comparisons were performed with separate Wilcoxon signed-rank tests to determine which sensory conditions were significantly different from each other. Bonferroni’s correction was used with α=0.0083 to compensate for multiple comparisons.

Furthermore, mean perception ranking scores and corresponding standard deviations were calculated by Microsoft Excel. A Friedman ANOVA was conducted in SPSS per sensory condition for both milk and quark to test the effect of fat level and sensory condition on fat perception. Pairwise comparisons were performed by separate Wilcoxon signed-rank tests with Bonferroni’s adjustment (α=0.0083) to assess whether the mean perception ranking scores differed significantly between fat levels.

2.5.3 Preference data analysis In order to test the effect of fat levels on fat preference, the mean preference ranking scores and corresponding standard deviations were calculated by Microsoft Excel for every sample. A Friedman ANOVA for repeated measures non-parametric data was performed in SPSS per sensory condition for both milk and quark. Pairwise comparisons were performed with separate Wilcoxon signed-rank tests to assess whether the mean preference ranking scores differed between fat levels. To compensate for multiple comparisons, Bonferroni’s adjustment was used with α=0.0083 (α=0.05/6 pairwise comparisons). Other Friedman ANOVA’s were used to test the effect of sensory conditions on fat preference for both milk and quark. Besides, multiple Wilcoxon signed-rank tests were conducted to assess significant differences in preference between milk and quark.

Concerning the number of times a certain sample was most preferred, multiple binomial tests were conducted in PQRS to test if a sample was significantly more preferred than others. A binomial distribution was used with n=50 as in total 50 participants performed the test and p=0.25 because each sample had a probability of 0.25 being most preferred.

In addition, chi-square tests were performed to assess significant differences between frequencies of preference in the different sensory conditions. These tests were done using the CHISQ.TEST function in Microsoft Excel.

3 Results

3.1 Instrumental measurements results

3.1.1 Viscosity results The viscosity curves of all milk and quark samples with different fat levels ranging from 0.0% to 10.0% are presented in figure 3. It can be seen that the viscosity of the quark samples is much higher than the viscosity of the milk samples. As a result, output of the independent samples t-test showed that the viscosity of milk and quark was significantly different (p=0.000) (see appendix 2.1).

Upon visual inspection of the different curves in figure 3A, the viscosity of all milk samples does not clearly increase or decrease under increasing shear rate, thus is independent on shear rate, which shows Newtonian behaviour. When looking at the different fat levels, the viscosity of the milk samples increases with a higher fat level; especially milk samples with a fat content of 6.0% and 10.0% show a


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higher viscosity. The viscosity of other milk samples (with a fat content of 0.0%, 1.5%, 3.0% and 4.5%) appear to be quite similar. Results of the one-way ANOVA confirm this as there was found a significant difference between the milk samples (p=0.000) (see appendix 2.2). According to results of Tukey’s post hoc test for pairwise comparison, milk samples with a fat content of 6.0% and 10.0% differed significantly from other milk samples. The corresponding mean viscosity values for all milk samples under an increasing shear rate from 0.1 to 500 s-1 can be found in table 4.

Regarding the quark samples, viscosity decreases by increasing shear rate, which indicates shear thinning behaviour (see figure 3B). In addition, the viscosity of the quark decreases with increasing fat content. The viscosity of the quark samples with a fat content of 1.5%, 3.0%, 4.5%, 6.0% and 10.0% is quite similar. Quark with a fat content of 0.0% shows a higher viscosity. This is confirmed by results of the one-way ANOVA showing a significant difference between the viscosity of the quark samples (p=0.004) (see appendix 2.2). Also results of Tukey’s post hoc test for pairwise comparison demonstrate a significant difference between the viscosity of the 0.0% fat quark sample and the viscosity of other quark samples, except for 3.0% fat quark. The corresponding mean viscosity values for all quark samples at a shear rate of 50 s-1 can be found in table 5.

Figure 3: Viscosity curves of milk samples (A) and quark samples (B) with six different fat levels measured at 20 °C under increasing shear rate from 0.1 to 500 s-1.

0

1

2

3

4

0 100 200 300 400 500

Visc

osity

(mPa･s

)

Shear rate (1/s)

0.0% fat milk1.5% fat milk3.0% fat milk4.5% fat milk6.0% fat milk10.0% fat milk

0

500

1000

1500

2000

2500

3000

3500

0 100 200 300 400 500

Visc

osity

(mPa･

s)

Shear rate (1/s)

0.0% fat quark1.5% fat quark3.0% fat quark4.5% fat quark6.0% fat quark10.0% fat quark

0 100 200 300 400 500

0 100 200 300 400 500

A) Milk

B) Quark


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Table 4: Means and standard deviations of viscosity of milk samples with six different fat levels under increasing shear rate from 0.1 to 500 s-1.

Fat content (% w/w)

Mean viscosity (mPa∙s)

0.0 2.13 ± 0.02 1.5 2.29 ± 0.03 3.0 2.35 ± 0.06 4.5 2.44 ± 0.02 6.0 2.81 ± 0.02

10.0 3.43 ± 0.02 Table 5: Means and standard deviations of viscosity of quark samples with six different fat levels at a shear rate of 50 s-1.

Fat content (% w/w)

Mean viscosity (mPa∙s)

0.0 2129 ± 39 1.5 1788 ± 79 3.0 1870 ± 1 4.5 1747 ± 155 6.0 1634 ± 48

10.0 1589 ± 56 3.1.2 Tribology results In figure 4A and 4B the Stribeck curves of all milk and quark samples with six different fat levels are shown. There is no clear difference seen between the milk and quark samples. Concerning the different fat levels, it can be seen from the curves that the friction factor of both milk and quark samples decreases with a higher fat level, which indicates that fat acts as a lubricant.

0,0

0,1

0,2

0,3

0,4

0,5

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Figure 4: Stribeck curves of milk samples (A) and quark samples (B) with six different fat levels measured at 20 °C under increasing sliding velocity from 1∙10-6 to 1 m/s. 3.2 Fat perception test results After calculating the discrimination scores from the ranking orders, a mean discrimination ability score was calculated per sensory condition for both milk and quark. These mean discrimination ability scores with corresponding standard deviations are graphically presented in figure 5. Because the ranking data was ordinal and results of the Shapiro-Wilk test showed that the data was not normally distributed (see appendix 3.1), non-parametric tests were conducted in SPSS to analyse the data.

Figure 5 illustrates that in the orthonasal smell condition, the mouthfeel condition and the smell + mouthfeel condition the mean discrimination ability scores were significantly different from zero for both milk and quark. The corresponding SPSS output of the one sample Wilcoxon signed-rank tests against zero can be found in appendix 3.2. This indicates that participants were able to rank the samples in the correct order and did not rank them randomly in these conditions. Only in the retronasal smell condition the mean discrimination ability scores did not show to be significantly different from zero for both milk and quark (p=0.251 and p=0.449 respectively).

Results of the Wilcoxon signed-rank test showed that the mean discrimination ability scores were significantly higher for milk than for quark (p=0.008) (see appendix 3.3). However, when looking at the different sensory conditions, this effect was only significantly proved in the mouthfeel condition (p=0.046). In the other conditions no significant differences between milk and quark were found (orthonasal smell, p=0.059; retronasal smell, p=0.736; smell + mouthfeel, p=0.210) (see appendix 3.4).

Furthermore, output of the Friedman ANOVA’s revealed that for both milk and quark the mean discrimination ability scores differed significantly between the different sensory conditions (see appendix 3.5). However, when applying pairwise comparisons by Wilcoxon signed-rank tests with Bonferroni’s adjustment (p<0.0083), only for milk was found that the mean discrimination ability scores were significantly lower in the retronasal smell condition compared to the other conditions (see appendix 3.6). For quark, no significant differences were found with Bonferroni’s adjustment.

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Figure 5: Mean discrimination ability scores and standard deviations under different sensory conditions for milk and quark. Mean discrimination ability scores not sharing a common letter differed significantly with Bonferroni’s adjustment (p<0.0083) between sensory conditions within milk or quark. A significant difference from zero is indicated with a star symbol (*).

Furthermore, mean perception ranking scores and corresponding standard deviations were calculated by Microsoft Excel. Figure 6 visually demonstrates these mean perception ranking scores per fat level under the different sensory conditions for milk and quark. It can be seen that for both milk and quark samples the mean perception ranking scores increase by increasing fat level in the orthonasal smell condition, the mouthfeel condition and the smell + mouthfeel condition, indicating that participants were able to discriminate the different fat content samples in these conditions for both milk and quark. This is confirmed by the results of the Friedman ANOVA’s, showing significant differences between fat levels in the orthonasal smell condition, the mouthfeel condition and the smell + mouthfeel condition for both milk and quark (orthonasal smell – milk, p=0.000; mouthfeel – milk, p=0.000; smell + mouthfeel – milk, p=0.000; orthonasal smell – quark, p=0.001; mouthfeel – quark, p=0.001; smell + mouthfeel – quark, p=0.000). In the retronasal smell condition no significant differences between fat levels were found (retronasal smell – milk, p=0.227; retronasal smell – quark, p=0.392) (see appendix 3.7).

According to results of the pairwise comparisons with separate Wilcoxon signed-rank tests, the fat discrimination ability of humans seems to be better for milk than for quark as in general more pairs could be discriminated for milk than for quark (see appendix 3.8). To be precise, two more pairs could be discriminated for milk than for quark in the orthonasal smell condition as well as in the mouthfeel condition and in the smell + mouthfeel condition. Besides, the discrimination ability seems to be the best in the mouthfeel and smell + mouthfeel condition as an additional pair could be discriminated in these conditions compared to the orthonasal smell condition for both milk and quark.

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18

Figure 6: Mean perception ranking scores and standard deviations per fat level under different sensory conditions for milk (A) and quark (B). Mean perception ranking scores not sharing a common letter differed significantly with Bonferroni’s adjustment (p<0.0083) between fat levels within one sensory condition. 3.3 Fat preference test results In figure 7 the mean preference ranking scores are graphically presented per fat level under the four different sensory conditions for milk and quark. For milk, it can be seen that the mean preference ranking score is increasing with increasing fat level in the mouthfeel condition and smell + mouthfeel condition. Also quark samples show this phenomenon in the mouthfeel condition. However, results of multiple Friedman ANOVA’s did not show any significant differences between fat levels within one sensory condition for both milk and quark, except for quark samples in the retronasal smell condition (orthonasal smell – milk, p=0.652; retronasal smell – milk, p=0.323; mouthfeel – milk, p=0.463; smell + mouthfeel – milk, p=0.183; orthonasal smell – quark, p=0.079; retronasal smell – quark, p=0.036; mouthfeel – quark, p=0.097; smell + mouthfeel – quark, p=0.119) (see appendix 4.1). However, results of the pairwise comparisons by Wilcoxon signed-rank tests with Bonferroni’s

a

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19

adjustment (p<0.0083) did not show any significant differences within the retronasal smell condition for quark (see appendix 4.2).

In order to test the effect of sensory conditions on fat preference, a Friedman ANOVA was performed for both milk and quark (see appendix 4.3). No significant difference in preference between sensory conditions was found for both milk and quark (p=0.905 and p=0.744 respectively). Besides, results of the Wilcoxon signed-rank tests also did not show significant difference in preference between milk and quark under the four different sensory conditions (orthonasal smell, p=0.906; retronasal smell, p=0.880; mouthfeel, p=0.930; smell + mouthfeel, p=0.960) (see appendix 4.4).

Figure 7: Mean preference ranking scores and standard deviations per fat level under four different sensory conditions for milk (A) and quark (B).

Figure 8 shows the number of times that a certain sample was chosen to be most preferred. For the milk samples, no significant differences were found between fat levels and between sensory conditions (see appendix 4.5 and 4.6). This means that participants did not have a significant preference for a specific milk sample in all sensory conditions. For the quark samples, two samples were significantly

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20

different; 6.0% fat quark was significantly more preferred in the mouthfeel condition (p=0.006) and 3.0% fat quark was significantly less preferred in the smell + mouthfeel condition (p=0.019). In addition, results of the chi-square tests showed that frequency distributions of preferences for quark differed significantly between the following sensory conditions: orthonasal smell and mouthfeel, orthonasal smell and smell + mouthfeel, retronasal smell and mouthfeel, and mouthfeel and smell + mouthfeel (p=0.004, p=0.015, p=0.013 and p=0.004 respectively).

Figure 8: Frequency distributions of preferences for fat levels under different sensory conditions for milk (A) and quark (B). Frequency distributions of preferences not sharing a common letter differed significantly (p<0.05) between sensory conditions. A significant difference between fat levels within one sensory condition is indicated with a star symbol (*).

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21

4 Discussion

4.1 Insights from the fat perception test Results of the fat perception test showed that participants were able to rank 1.5%, 3.0%, 4.5% and 6.0% fat content samples in the correct order in both milk and quark when only orthonasal smell cues, only mouthfeel cues and both smell and mouthfeel cues were available. Although participants were able to discriminate the samples by orthonasal smell and mouthfeel, fat discrimination ability was not increased when both smell and mouthfeel cues were present. In addition, participants were not able to correctly rank the samples in the retronasal smell condition. Further research is needed to examine whether participants are actually not able to discriminate the samples when only retronasal smell cues are present or that this is due to the performance of participants in this study. It might be that participants were not familiarised enough to use the modified odour containers in combination with the nose clips in the correct way, but it is not clear if this had a significant impact on the results.

Other results of the perception test demonstrated that fat discrimination was significantly easier for milk than quark. This is in agreement with results of other studies proving that it is easier to discriminate different fat levels in low viscous products compared to high viscous products (Drewnowski, Shrager, Lipsky, Stellar, & Greenwood, 1989; Le Calvé et al., 2015). In addition, this effect was only significantly proved in the mouthfeel condition, suggesting that this effect might be larger when only mouthfeel cues are present.

In order to better understand the fat discrimination ability of participants, viscosity and tribology of the food products used in this study were measured. Results of the rheological measurements showed that the viscosities of the milk samples were significantly lower than the viscosities of the quark samples. This means that it is allowed to mention milk as the low viscous product and quark as the high viscous product in this study. When looking at the different fat levels, the mean viscosity values of milk samples with a fat content of 1.5%, 3.0% and 4.5% appeared to be quite similar (2.29 mPa∙s, 2.35 mPa∙s and 2.44 mPa∙s respectively). Milk with a fat content of 6.0% showed a significantly higher viscosity (2.81 mPa∙s). According to earlier research, a Weber fraction of 0.2 for viscosity of dairy-based emulsions was found, calculated from just noticeable differences in creaminess perception (Zahn, Hoppert, Ullrich, & Rohm, 2013). Applying this to the viscosity of 2.29 mPa∙s (1.5% fat milk), milk with a viscosity higher than 2.75 mPa∙s should be noticeable. This confirmed that 6.0% fat milk should be perceived differently compared to the other milk samples based on viscosity. However, as results of the fat perception test showed that participants were also able to discriminate other fat content milk samples, it can be stated that ranking of the milk samples was not based on viscosity only. Concerning quark, the mean viscosity values at a shear rate of 50 s-1 of samples with a fat content of 1.5%, 3.0%, 4.5% and 6.0% were quite similar and did not show any significant differences (1788 mPa∙s, 1870 mPa∙s, 1747 mPa∙s and 1634 mPa∙s respectively). This is also confirmed by applying a Weber fraction of 0.2 to a viscosity of 1634 mPa∙s (6.0% fat quark), quark with a viscosity of 1961 mPa∙s should be perceived differently, meaning that there was not any noticeable difference between the four different quark samples with regard to viscosity. Therefore, it is assumed that ranking of the different fat levels in quark was not based on viscosity.

Results of the fat perception test seem to be better explained by the outcomes of the tribology measurements. It was found that the friction factor decreased with a higher fat level for both milk and quark samples. This can be explained by the fact that fat acts as a lubricant. During consumption, fat settles at the surface of the oral food bolus. Therefore, higher levels of fat migrating to the surface of the bolus cause a more fatty and creamy perception in the mouth (de Wijk & Prinz, 2005; de Wijk & Prinz, 2007). This could be an explanation for the fact that participants were able to correctly rank the different fat content samples when only mouthfeel cues and both smell and mouthfeel cues were available. However, the fat discrimination ability in the orthonasal and retronasal smell condition cannot be explained by friction as friction is a textural property of the food that is sensed within the


22

oral cavity and not perceived by smell. Further research is needed to unravel the exact underlying reason for the fat discrimination ability of humans. 4.2 Insights from the fat preference test This study could not proof significant differences in preference for any of the fat levels, except for quark in the mouthfeel condition. It was found that preference was increasing with higher fat level in the mouthfeel condition for both milk and quark. Although this finding was not significantly proved, this trend was also seen when looking at the number of times that a certain sample was chosen to be most preferred. Frequency distributions of preferences for quark differed significantly between the mouthfeel condition and other conditions. Moreover, the highest fat content quark sample (6.0% fat quark) was significantly more preferred compared to other quark samples with a lower fat content in the mouthfeel condition. This is in line with findings of recent research demonstrating that patients suffering from congenital smell loss, and thus perceiving foods by mouthfeel cues only, have a higher preference for fatty foods compared to healthy people who perceive foods by both smell and mouthfeel cues (Postma at al., 2020). However, more research combining fat preference and mouthfeel is required as results of the fat preference test did not provide sufficient significant insights to draw firm conclusions.

Additionally, the fat preference data is supported by results of the tribology measurements. As earlier described, the friction factor of both milk and quark samples decreased with a higher fat level, which can be explained by the lubrication properties of fat. Fat can enhance creaminess by the settling of fat at the surface of the oral food bolus while eating, which reduces the friction between the bolus and the oral tissue. As it is known that humans associate creaminess with a pleasant sensation and a high quality of the food product, consequently humans prefer a higher fat level in the mouthfeel condition (Akhtar et al., 2005). Thus, the tribology data suggests that friction factors could be used as instrumental parameters related to fat preference. However, this cannot be stated with any certainty as not all earlier described fat preference results were significant. Further research coupling sensory and tribological characterisation would help to optimise the perception of low fat foods compared to high fat foods.

Findings of this study showed that participants did not have a clear preference for specific fat levels under the four different sensory conditions. This suggests that there are other stronger influencers on fat preference than fat itself, causing passive overconsumption of fat. Results of other studies revealed that sugar and salt have a larger impact on food liking than fat and thereby promote passive overconsumption of fat in humans (Bolhuis et al., 2015; Bolhuis et al., 2018). Furthermore, this study showed that fat discrimination was more difficult in high viscous foods compared to low viscous foods, suggesting that fat may be easier overconsumed in high viscous food products. Hence, in order to combat obesity, food product development is encouraged to take this knowledge into account.

4.3 Recommendations There were a few limitations in this study. First, this study included participants from 18 different nationalities. This is because the following criteria were given more importance than nationality: being familiar with milk and quark by means of consuming both milk and quark at least once a month, an age between 18 and 40 years, a BMI between 18.5 and 27.5 kg/m2 and a sample size of at least 50 participants. For future research, it would be recommended to include a smaller variety of nationalities to obtain a more homogenous group of participants and exclude a possible effect on the results due to nationality. Another limitation was that only 11 students of the 70 students that were selected according to the inclusion and exclusion criteria were male, and therefore excluded. As a consequence, only female students were selected to participate in the sensory test. It is recommended for further research to also include males to get a more realistic representation of the population. In addition, for both perception and preference testing, participants were asked to rinse their mouth with


23

water after each sample. However, some participants stated that they could not sufficiently cleanse their palate by drinking water. For this reason, it is recommended to provide participants also with plain crackers to make sure that they will clean their palate properly in between tasting the samples.

Results of this study indicated that mouthfeel might play a bigger role in fat perception compared to smell. Therefore, it is recommended to deepen that knowledge by further investigation. Another recommendation is to conduct more research into fat perception by retronasal smell. It would be advisable to familiarise participants with the use of a nose clip and a modified odour container in a separate training session organised prior to the sensory tests. In this way, participants will get used to breathing through a modified odour container and using a nose clip at the same time.

Besides, further research should also focus on the influence of viscosity on just noticeable differences in fat content. Present research findings suggested that fat discrimination is better in low viscous foods compared to high viscous foods. Until now, there is only a small body of research that examined just noticeable differences in fat content (Mela, 1988; Schiffman et al., 1998). It is unclear whether there is a certain viscosity value from which fat discrimination is highly decreased or even not possible anymore. Unravelling this knowledge would help to better understand why fat is easily overconsumed by humans and thereby causing obesity.

5 Conclusion

In this research, the influence of smell and mouthfeel cues on fat perception and preference in low and high viscous food products was investigated. Outcomes demonstrated that humans are able to discriminate samples with varying fat content from 1.5% till 6.0% by orthonasal smell only, by mouthfeel only and by combining smell and mouthfeel in both low and high viscous food products. Although humans are able to discriminate fat by orthonasal smell and mouthfeel, fat discrimination ability is not increased when both smell and mouthfeel cues are present. When only retronasal smell cues are available, fat discrimination seems to be more difficult. In addition, fat discrimination seems to be more difficult in high viscous foods compared to low viscous foods, meaning that fat may be easier overconsumed in high viscous food products. Results suggest that this effect might be larger when only mouthfeel cues are present.

Concerning fat preference, findings could not proof a significant difference in preference, except for quark in the mouthfeel condition. It seemed that humans prefer a higher fat level when only mouthfeel cues are available. It was shown that frequency distributions of preferences for quark differed significantly between the mouthfeel condition and other conditions. Moreover, the highest fat content quark sample (6.0% fat quark) was significantly more preferred compared to other quark samples with a lower fat content in the mouthfeel condition.

Furthermore, findings of the fat perception and preference tests seem to be explained by the tribological properties of the food products used in this study, and not by viscosity. It seemed that fat perception and preference were based on friction when only mouthfeel cues were present.

To summarise briefly, it was shown that although humans were able to discriminate different fat levels, they did not have a clear preference for specific fat levels. This suggests that not fat itself but other influencers such as sugar and salt might affect fat preference and thereby promote passive overconsumption of fat.

For future research it is recommended to further examine the effect of mouthfeel on fat perception and preference as this sensory modality seems to contribute relatively more to fat perception and preference compared to olfactory sensations.


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Acknowledgements

To write this thesis as one of the last steps in my student career was a great experience, but I would not have succeeded without the people who helped and supported me. First of all, I would like to thank my supervisor Dieuwerke Bolhuis for her guidance through each stage of my thesis. Thank you for your insights and enthusiasm, which were very valuable to me. In addition to my supervisor, I would like to thank my thesis partner Mirjam Hemelaar. I really enjoyed working together on this study. Furthermore, I also want to thank Annelies Blok and Harry Baptist for helping me with the tribology measurements. Finally, I would like to thank my friends and family for their encouragement and support throughout the process of writing my thesis.


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Appendices

Appendix 1: Example questionnaires

Appendix 1.1: Example questionnaire fat preference Name: __________________________________________ Date: _________________ Participant number: 1 Testing method: smelling with your mouth You are provided with a total of 4 quark samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Put on your nose clip. Open the cap from the tube placed in the container. Inhale once via the straw. Keep your lips closed, remove your nose clip and exhale through your nose while keeping your lips closed. Place the samples in increasing order of preference in the table.

Most preferred Second most preferred Second least preferred Least preferred

Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your nose You are provided with a total of 4 milk samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Smell/inhale the samples with your nose when closing your mouth. Exhale through your nose. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: regular tasting You are provided with a total of 4 milk samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your mouth You are provided with a total of 4 milk samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Put on your nose clip. Open the cap from the tube placed in the container. Inhale once via the straw. Keep your lips closed, remove your nose clip and exhale through your nose while keeping your lips closed. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples.


28

Name: __________________________________________ Date: _________________ Participant number: 1 Testing method: tasting with a nose clip You are provided with a total of 4 milk samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples while wearing your nose clip. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your nose You are provided with a total of 4 quark samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Smell/inhale the samples with your nose when closing your mouth. Exhale through your nose. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: regular tasting You are provided with a total of 4 quark samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of preference in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: tasting with a nose clip You are provided with a total of 4 quark samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples while wearing your nose clip. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of preference in the table.


Please answer the last question on the next page.


29

Name: __________________________________________ Date: _________________ Participant number: 1 What did you eat for breakfast (and lunch)? _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Please press the button when you finished all the questions. Thank you for participating and see you soon for the second test session!


30

Appendix 1.2: Example questionnaire fat perception Name: __________________________________________ Date: _________________ Participant number: 1 Testing method: regular tasting You are provided with a total of 6 milk samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of fattiness between the reference samples in the table.

1st = least fatty 2nd 3rd 4th 5th 6th = most fatty 0% 10%

Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your mouth You are provided with a total of 6 milk samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Put on your nose clip. Open the cap from the tube placed in the container. Inhale once via the straw. Keep your lips closed, remove your nose clip and exhale through your nose while keeping your lips closed. Repeat this procedure for every sample. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: regular tasting You are provided with a total of 6 quark samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: tasting with a nose clip You are provided with a total of 6 quark samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples while wearing your nose clip. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples.


31

Name: __________________________________________ Date: _________________ Participant number: 1 Testing method: smelling with your nose You are provided with a total of 6 milk samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Smell/inhale the samples with your nose when closing your mouth. Exhale through your nose. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your nose You are provided with a total of 6 quark samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Smell/inhale the samples with your nose when closing your mouth. Exhale through your nose. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: tasting with a nose clip You are provided with a total of 6 milk samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Taste the samples while wearing your nose clip. You are allowed to swallow them. Please make sure that you rinse your mouth with water after each sample. Place the samples in increasing order of fattiness between the reference samples in the table.


Please press the button when you finished the table and wait until you get new samples. Testing method: smelling with your mouth You are provided with a total of 6 quark samples: 2 reference samples labelled 0% and 10% fat and 4 samples each labelled with a 3-digit code. Please assess the samples in the order provided from left to right. Put on your nose clip. Open the cap from the tube placed in the container. Inhale once via the straw. Keep your lips closed, remove your nose clip and exhale through your nose while keeping your lips closed. Repeat this procedure for every sample. Place the samples in increasing order of fattiness between the reference samples in the table.


Please answer the last question on the next page.


32

Name: __________________________________________ Date: _________________ Participant number: 1 What did you eat for breakfast (and lunch)? __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Please press the button when you finished all the questions. Thank you for participating!


33

Appendix 2: Results of the instrumental data analysis

Appendix 2.1: SPSS output of the independent samples t-test to compare viscosity of milk and quark samples

Independent Samples Test

Levene's Test for

Equality of Variances t-test for Equality of

Means

F Sig. t df Sig.

(2-tailed) Viscosity Equal variances assumed 7.666 .020 -22.626 10 .000

Equal variances not assumed -22.626 5 .000

Appendix 2.2: SPSS output of the one-way ANOVA’s with Tukey’s post hoc tests to compare viscosity of milk and quark samples regarding fat level

Milk

ANOVA Viscosity - Milk Sum of Squares df Mean Square F Sig. Between Groups 2.234 5 .447 144.159 .000 Within Groups .019 6 .003

Total 2.253 11

Multiple Comparisons Dependent Variable: Viscosity - Milk Tukey HSD

(I) Fat level (J) Fat level Mean

Difference (I-J) Std. Error Sig. 95% Confidence Interval

Lower Bound Upper Bound 0.0% fat 1.5% fat -.16000 .05568 .169 -.3816 .0616

3.0% fat -.21500 .05568 .057 -.4366 .0066 4.5% fat -.31000* .05568 .011 -.5316 -.0884 6.0% fat -.67500* .05568 .000 -.8966 -.4534 10.0% fat -1.29000* .05568 .000 -1.5116 -1.0684

1.5% fat 0.0% fat .16000 .05568 .169 -.0616 .3816 3.0% fat -.05500 .05568 .906 -.2766 .1666 4.5% fat -.15000 .05568 .206 -.3716 .0716 6.0% fat -.51500* .05568 .001 -.7366 -.2934 10.0% fat -1.13000* .05568 .000 -1.3516 -.9084

3.0% fat 0.0% fat .21500 .05568 .057 -.0066 .4366 1.5% fat .05500 .05568 .906 -.1666 .2766 4.5% fat -.09500 .05568 .572 -.3166 .1266 6.0% fat -.46000* .05568 .001 -.6816 -.2384


34

10.0% fat -1.07500* .05568 .000 -1.2966 -.8534 4.5% fat 0.0% fat .31000* .05568 .011 .0884 .5316

1.5% fat .15000 .05568 .206 -.0716 .3716 3.0% fat .09500 .05568 .572 -.1266 .3166 6.0% fat -.36500* .05568 .005 -.5866 -.1434 10.0% fat -.98000* .05568 .000 -1.2016 -.7584

6.0% fat 0.0% fat .67500* .05568 .000 .4534 .8966 1.5% fat .51500* .05568 .001 .2934 .7366 3.0% fat .46000* .05568 .001 .2384 .6816 4.5% fat .36500* .05568 .005 .1434 .5866 10.0% fat -.61500* .05568 .000 -.8366 -.3934

10.0% fat 0.0% fat 1.29000* .05568 .000 1.0684 1.5116 1.5% fat 1.13000* .05568 .000 .9084 1.3516 3.0% fat 1.07500* .05568 .000 .8534 1.2966 4.5% fat .98000* .05568 .000 .7584 1.2016 6.0% fat .61500* .05568 .000 .3934 .8366

*. The mean difference is significant at the 0.05 level.

Quark

ANOVA Viscosity - Quark Sum of Squares df Mean Square F Sig. Between Groups 375581.757 5 75116.351 12.143 .004 Within Groups 37116.470 6 6186.078

Total 412698.227 11

Multiple Comparisons Dependent Variable: Viscosity - Quark Tukey HSD

(I) Fat level (J) Fat level Mean

Difference (I-J) Std. Error Sig. 95% Confidence Interval

Lower Bound Upper Bound 0.0% fat 1.5% fat 340.50000* 78.65163 .035 27.4786 653.5214

3.0% fat 258.60000 78.65163 .106 -54.4214 571.6214 4.5% fat 382.05000* 78.65163 .021 69.0286 695.0714 6.0% fat 494.90000* 78.65163 .006 181.8786 807.9214 10.0% fat 539.75000* 78.65163 .004 226.7286 852.7714

1.5% fat 0.0% fat -340.50000* 78.65163 .035 -653.5214 -27.4786 3.0% fat -81.90000 78.65163 .888 -394.9214 231.1214 4.5% fat 41.55000 78.65163 .993 -271.4714 354.5714 6.0% fat 154.40000 78.65163 .450 -158.6214 467.4214


35

10.0% fat 199.25000 78.65163 .247 -113.7714 512.2714 3.0% fat 0.0% fat -258.60000 78.65163 .106 -571.6214 54.4214

1.5% fat 81.90000 78.65163 .888 -231.1214 394.9214 4.5% fat 123.45000 78.65163 .642 -189.5714 436.4714 6.0% fat 236.30000 78.65163 .146 -76.7214 549.3214 10.0% fat 281.15000 78.65163 .077 -31.8714 594.1714

4.5% fat 0.0% fat -382.05000* 78.65163 .021 -695.0714 -69.0286 1.5% fat -41.55000 78.65163 .993 -354.5714 271.4714 3.0% fat -123.45000 78.65163 .642 -436.4714 189.5714 6.0% fat 112.85000 78.65163 .711 -200.1714 425.8714 10.0% fat 157.70000 78.65163 .432 -155.3214 470.7214

6.0% fat 0.0% fat -494.90000* 78.65163 .006 -807.9214 -181.8786 1.5% fat -154.40000 78.65163 .450 -467.4214 158.6214 3.0% fat -236.30000 78.65163 .146 -549.3214 76.7214 4.5% fat -112.85000 78.65163 .711 -425.8714 200.1714 10.0% fat 44.85000 78.65163 .990 -268.1714 357.8714

10.0% fat 0.0% fat -539.75000* 78.65163 .004 -852.7714 -226.7286 1.5% fat -199.25000 78.65163 .247 -512.2714 113.7714 3.0% fat -281.15000 78.65163 .077 -594.1714 31.8714 4.5% fat -157.70000 78.65163 .432 -470.7214 155.3214 6.0% fat -44.85000 78.65163 .990 -357.8714 268.1714

*. The mean difference is significant at the 0.05 level.

Appendix 3: Results of the perception data analysis

Appendix 3.1: SPSS output of the tests of normality for the discrimination scores of milk and quark under four different sensory conditions

Tests of Normality

Condition Kolmogorov-Smirnova Shapiro-Wilk

Statistic df Sig. Statistic df Sig. Discrimination scores

Orthonasal smell .174 100 .000 .928 100 .000 Retronasal smell .138 100 .000 .951 100 .001 Mouthfeel .187 100 .000 .918 100 .000 Smell+mouthfeel .186 100 .000 .906 100 .000

a. Lilliefors Significance Correction Tests of Normality

Product Kolmogorov-Smirnova Shapiro-Wilk

Statistic df Sig. Statistic df Sig. Discrimination scores Milk .178 200 .000 .920 200 .000

Quark .167 200 .000 .940 200 .000 a. Lilliefors Significance Correction


36

Appendix 3.2: SPSS output of the one sample Wilcoxon signed-rank tests against zero

Hypothesis Test Summary Null Hypothesis Test Sig. Decision 1 The median of Orthonasal

smell - Milk equals 0. One-Sample Wilcoxon Signed Rank Test

.000 Reject the null hypothesis.

2 The median of Retronasal smell - Milk equals 0.

One-Sample Wilcoxon Signed Rank Test

.251 Retain the null hypothesis.

3 The median of Mouthfeel - Milk equals 0.



4 The median of Smell + mouthfeel - Milk equals 0.



5 The median of Orthonasal smell - Quark equals 0.



6 The median of Retronasal smell - Quark equals 0.


.449 Retain the null hypothesis.

7 The median of Mouthfeel - Quark equals 0.



8 The median of Smell + mouthfeel - Quark equals 0.



Asymptotic significances are displayed. The significance level is .050. Appendix 3.3: SPSS output of the Wilcoxon signed-rank test to compare discrimination ability scores between milk and quark

Test Statisticsa

Discrimination score - Quark

– Discrimination

score - Milk Z -2.669b Asymp. Sig. (2-tailed) .008 a. Wilcoxon Signed Ranks Test b. Based on positive ranks.


37

Appendix 3.4: SPSS output of the Wilcoxon signed-rank tests to compare discrimination ability scores between milk and quark under four different sensory conditions

Test Statisticsa

Discrimination score -

Orthonasal smell - Quark

– Discrimination

score - Orthonasal smell

- Milk


Retronasal smell - Quark

– Discrimination

score - Retronasal smell

- Milk


Mouthfeel - Quark

– Discrimination

score - Mouthfeel

- Milk

Discrimination score - Smell +

mouthfeel - Quark

– Discrimination score - Smell +

mouthfeel - Milk

Z -1.889b -.337b -1.992b -1.253b Asymp. Sig. (2-tailed) .059 .736 .046 .210 a. Wilcoxon Signed Ranks Test b. Based on positive ranks.

Appendix 3.5: SPSS output of the Friedman ANOVA’s to compare discrimination ability scores between four different sensory conditions for milk and quark

Milk: Test Statisticsa

N 50 Chi-Square 15.729 df 3 Asymp. Sig. .001 a. Friedman Test

Quark: Test Statisticsa


Appendix 3.6: SPSS output of the pairwise comparisons of the discrimination ability scores by Wilcoxon signed-rank tests under four different sensory conditions for milk and quark

Test Statisticsa

Retronasal smell - Milk

–Orthonasal

smell - Milk

Mouthfeel - Milk

– Orthonasal

smell - Milk

Smell + mouthfeel

- Milk –

Orthonasal smell -

Milk

Mouthfeel - Milk

– Retronasal

smell - Milk

Smell + mouthfeel

- Milk –

Retronasal smell -

Milk

Smell + mouthfeel

- Milk –

Mouthfeel - Milk

Z -3.346b -.213c -.134b -3.360c -3.095c -.193b Asymp. Sig. (2-tailed) .001 .831 .894 .001 .002 .847 a. Wilcoxon Signed Ranks Test b. Based on positive ranks. c. Based on negative ranks.


38

Test Statisticsa

Retronasal smell

- Quark –


Mouthfeel - Quark

– Orthonasal

smell - Quark

Smell + mouthfeel

- Quark –


Mouthfeel - Quark

– Retronasal

smell - Quark

Smell + mouthfeel

- Quark –


Smell + mouthfeel

- Quark –

Mouthfeel - Quark

Z -2.257b -.494c -.482c -2.056c -2.329c -.151c Asymp. Sig. (2-tailed) .024 .622 .629 .040 .020 .880 a. Wilcoxon Signed Ranks Test b. Based on positive ranks. c. Based on negative ranks.

Appendix 3.7: SPSS output of the Friedman ANOVA’s of the perception ranking scores per sensory condition for milk and quark

Milk

Orthonasal smell: Test Statisticsa

N 50 Chi-Square

36.264

df 3 Asymp. Sig.

.000

a. Friedman Test

Retronasal smell: Test Statisticsa

N 50 Chi-Square

4.344

df 3 Asymp. Sig.

.227

a. Friedman Test

Mouthfeel: Test Statisticsa

N 50 Chi-Square

40.248

df 3 Asymp. Sig.

.000

a. Friedman Test

Smell + mouthfeel: Test Statisticsa

N 50 Chi-Square

37.224

df 3 Asymp. Sig.

.000

a. Friedman Test

Quark


N 50 Chi-Square

16.344

df 3 Asymp. Sig.

.001

a. Friedman Test


N 50 Chi-Square

3.000

df 3 Asymp. Sig.

.392

a. Friedman Test


N 50 Chi-Square

17.064

df 3 Asymp. Sig.

.001

a. Friedman Test


N 50 Chi-Square

19.128

df 3 Asymp. Sig.

.000

a. Friedman Test


39

Appendix 3.8: SPSS output of the pairwise comparisons of the perception ranking scores of four fat levels by Wilcoxon signed-rank tests under the orthonasal smell condition, the mouthfeel condition and the smell + mouthfeel condition for milk and quark

Test Statisticsa

3.0% fat - Orthonasal

smell - Milk

– 1.5% fat -

Orthonasal smell -

Milk


smell - Milk

– 1.5% fat -

Orthonasal smell -

Milk


smell - Milk

– 1.5% fat -

Orthonasal smell -

Milk


smell - Milk

– 3.0% fat -

Orthonasal smell -

Milk


smell - Milk

– 3.0% fat -

Orthonasal smell -

Milk


smell - Milk

– 4.5% fat -

Orthonasal smell -

Milk Z -2.601b -4.298b -4.965b -1.248b -2.803b -2.123b Asymp. Sig. (2-tailed) .009 .000 .000 .212 .005 .034 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.

Test Statisticsa

3.0% fat - Mouthfeel

- Milk –


- Milk


- Milk –


- Milk


- Milk –


- Milk


- Milk –


- Milk


- Milk –


- Milk


- Milk –


- Milk Z -.431b -3.661b -4.795b -3.047b -4.923b -1.676b Asymp. Sig. (2-tailed) .667 .000 .000 .002 .000 .094 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.


40

Test Statisticsa

3.0% fat - Smell +

mouthfeel - Milk

– 1.5% fat - Smell +

mouthfeel - Milk

4.5% fat - Smell +

mouthfeel - Milk


mouthfeel - Milk

6.0% fat - Smell +

mouthfeel - Milk


mouthfeel - Milk

4.5% fat - Smell +

mouthfeel - Milk


mouthfeel - Milk

6.0% fat - Smell +

mouthfeel - Milk


mouthfeel - Milk

6.0% fat - Smell +

mouthfeel - Milk


mouthfeel - Milk

Z -1.832b -3.461b -4.510b -3.009b -3.935b -1.237b Asymp. Sig. (2-tailed) .067 .001 .000 .003 .000 .216 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.

Test Statisticsa


smell - Quark

– 1.5% fat -



smell - Quark

– 1.5% fat -



smell - Quark

– 1.5% fat -



smell - Quark

– 3.0% fat -



smell - Quark

– 3.0% fat -



smell - Quark

– 4.5% fat -


Z -1.496b -2.389b -3.918b -.885b -2.422b -1.614b Asymp. Sig. (2-tailed) .135 .017 .000 .376 .015 .107 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.

Test Statisticsa


- Quark –


- Quark


- Quark –


- Quark


- Quark –


- Quark


- Quark –


- Quark


- Quark –


- Quark


- Quark –


- Quark Z -1.690b -2.771b -3.941b -1.350b -2.024b -1.140b Asymp. Sig. (2-tailed) .091 .006 .000 .177 .043 .254 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.


41

Test Statisticsa

3.0% fat - Smell +

mouthfeel - Quark


mouthfeel - Quark

4.5% fat - Smell +

mouthfeel - Quark


mouthfeel - Quark

6.0% fat - Smell +

mouthfeel - Quark


mouthfeel - Quark

4.5% fat - Smell +

mouthfeel - Quark


mouthfeel - Quark

6.0% fat - Smell +

mouthfeel - Quark


mouthfeel - Quark

6.0% fat - Smell +

mouthfeel - Quark

– 4.5% fat -

Smell + mouthfeel

- Quark Z -.154b -1.959b -3.326b -1.418b -3.303b -2.441b Asymp. Sig. (2-tailed) .878 .050 .001 .156 .001 .015 a. Wilcoxon Signed Ranks Test b. Based on negative ranks.

Appendix 4: Results of the preference data analysis

Appendix 4.1: SPSS output of the Friedman ANOVA’s of the preference ranking scores per sensory condition for milk and quark

Milk


N 50 Chi-Square 1.632 df 3 Asymp. Sig.

.652

a. Friedman Test



.323

a. Friedman Test



.463

a. Friedman Test



.183

a. Friedman Test

Quark



.079

a. Friedman Test



.036

a. Friedman Test



.097

a. Friedman Test



.119

a. Friedman Test


42

Appendix 4.2: SPSS output of the pairwise comparisons of the preference ranking scores of four fat levels by Wilcoxon signed-rank tests under the retronasal smell condition for quark

Test Statisticsa

3.0% fat -Retronasal

smell - Quark

– 1.5% fat -



smell - Quark

– 1.5% fat -



smell - Quark

– 1.5% fat -


4.5% fat - Retronasal

smell - Quark

– 3.0% fat -



smell - Quark

– 3.0% fat -



smell - Quark

– 4.5% fat -


Z -2.512b -1.869b -2.170b -.749c -.718c -.147c Asymp. Sig. (2-tailed) .012 .062 .030 .454 .473 .883 a. Wilcoxon Signed Ranks Test b. Based on positive ranks. c. Based on negative ranks.

Appendix 4.3: SPSS output of the Friedman ANOVA’s to compare preference ranking scores between four different sensory conditions for milk and quark

Milk: Test Statisticsa

N 200 Chi-Square .562 df 3 Asymp. Sig. .905 a. Friedman Test

Quark: Test Statisticsa


Appendix 4.4: SPSS output of the Wilcoxon signed-rank tests to compare preference ranking scores between milk and quark under four different sensory conditions

Test Statisticsa


– Orthonasal smell

- Milk


– Retronasal smell

- Milk

Mouthfeel - Quark

– Mouthfeel

- Milk

Smell + mouthfeel - Quark

– Smell + mouthfeel

- Milk Z -.118b -.151b -.088c -.051b Asymp. Sig. (2-tailed) .906 .880 .930 .960 a. Wilcoxon Signed Ranks Test b. Based on positive ranks. c. Based on negative ranks.


43

Appendix 4.5: Results of the binomial tests of the number of times a sample was most preferred under four different sensory conditions for milk and quark

Milk

Orthonasal smell: Fat level Number of

times most preferred

p-value

1.5% 8 0.091 3.0% 17 0.098 4.5% 13 0.489 6.0% 12 0.511

Retronasal smell: Fat level Number of


p-value

1.5% 12 0.511 3.0% 10 0.262 4.5% 17 0.098 6.0% 11 0.382

Mouthfeel: Fat level Number of


p-value

1.5% 9 0.164 3.0% 12 0.511 4.5% 14 0.363 6.0% 15 0.252

Smell + mouthfeel: Fat level Number of


p-value

1.5% 9 0.164 3.0% 11 0.382 4.5% 13 0.489 6.0% 17 0.098

Quark

Orthonasal smell: Fat level Number of


p-value

1.5% 9 0.164 3.0% 8 0.092 4.5% 16 0.163 6.0% 17 0.098

Retronasal smell: Fat level Number of


p-value

1.5% 11 0.382 3.0% 16 0.163 4.5% 14 0.363 6.0% 9 0.164

Mouthfeel: Fat level Number of


p-value

1.5% 9 0.164 3.0% 12 0.511 4.5% 8 0.092 6.0% 21 0.006

Smell + mouthfeel: Fat level Number of


p-value

1.5% 13 0.489 3.0% 6 0.019 4.5% 14 0.363 6.0% 17 0.098


44

Appendix 4.6: Results of the chi-square tests to compare the number of times a sample was most preferred between four different sensory conditions for milk and quark

Milk

Retronasal smell -

Milk –

Orthonasal smell -

Milk

Mouthfeel - Milk

– Orthonasal

smell - Milk

Smell + mouthfeel

- Milk –

Orthonasal smell -

Milk

Mouthfeel - Milk

– Retronasal

smell - Milk

Smell + mouthfeel

- Milk –

Retronasal smell -

Milk

Smell + mouthfeel

- Milk –

Mouthfeel - Milk

p-value 0.133 0.175 0.108 0.261 0.163 0.214

Quark


– Orthonasal

smell - Quark

Mouthfeel - Quark

– Orthonasal

smell - Quark

Smell + mouthfeel

- Quark –


Mouthfeel - Quark

– Retronasal

smell - Quark

Smell + mouthfeel

- Quark –


Smell + mouthfeel

- Quark –

Mouthfeel - Quark

p-value 0.057 0.004 0.015 0.013 0.057 0.004

the role of smell and mouthfeel cues on fat perception and

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