effects of inulin and oligofructose on the

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JFS M: Food Microbiology and Safety

Effects of Inulin andOligofructose on theRheological Characteristics and Probiotic CultureSurvival in Low-Fat Probiotic Ice Cream A.S. A KALIN AND D. ERISIR

ABSTRACT: The effects of supplementation of oligofructose or inulin on the rheological characteristics and survivalof Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 in low-fat ice cream stored at –18 ◦C for 90d were studied. Addition of oligofructose or inulin to ice cream mix significantly increased apparent viscosity andoverrun and developed the melting properties in ice cream during storage (P < 0.05). However, the highest increasein firmness, the lowest change in melting properties, and the longest 1st dripping time were obtained in probioticice cream containing inulin (P < 0.05). Some textural properties have also improved especially by the end of storage.Freezing process caused a significant decrease in the viabilityof Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 (P < 0.05). Oligofructose significantly improved the viability of L. acidophilus La-5 and B. animalis Bb-12 inice cream mix (P < 0.05). Although the viable numbers for both bacteria decreased throughout the storage,

the minimum level of 10

6

CFU/g was maintained for B. animalis Bb-12 in only ice cream with oligofructose during storage.Keywords: Bifidobacterium animalis Bb-12, inulin, Lactobacillus acidophilus La-5, low-fat ice cream, oligofruc-

tose

Introduction

Dairy products with incorporated probiotic bacteria are gaining

popularity and the probiotics comprise approximately 65%

of the world functional food market (Agrawal 2005). The species

of bacteria most commonly used in dairy products for probiotic

effect are Lactobacillus and Bifidobacterium (Saxelin and others

2005).Standards requiringa minimum of 106 to107 CFU/g of Lacto-bacillus acidophilus and/orbifidobacteria in fermented dairy prod-

ucts have been introduced by several food organizations worldwide

(Shah 2000). Therefore, it is important to ensure a high survival

rate of these bacteria during the product shelf life to maintain con-

sumer confidence in probiotic products (Saxelin and others 1999).

Ice cream seems suitable for delivering probiotics in human diet

because of its pleasant taste and attractive texture. However, in or-

der to ensure that the product provides an adequate content of

microorganisms, cells must survive in freezing and frozen storage.

Freezing and thawing cause various degrees of damage to cells, in-

cluding microorganism death, inhibition of its development, re-

duction, or interruption of metabolic activity (Davies and Obafemi

1985).Recent studies have focused on the survival of probiotic bac-

teria in ice cream produced by different techniques such as cul-

turing ice cream mix (Hekmat and McMahon 1992; Davidson and

others 2000; Akın 2005; Favaro-Trindade and others 2006), nonfer-

mented ice cream mix (Alamprese and others 2002; Haynes and

Playne 2002), or adding fermented milk to regular ice cream mix

(Christiansen and others 1996; Hagen and Narvhus 1999). Nondi-

MS 20070590 Submitted7/27/2007, Accepted2/7/2008.Authors arewith Ege Univ., Faculty of Agriculture, Dept. of Dairy Technology, 35100, Bornova,Izmir, Turkey. Direct inquiries to author Akalın (E-mail: sakalin21@

yahoo.com).

gestible food ingredients or prebiotics that selectively stimulate

growth and/or activity of probiotic bacteria have been used to in-

crease the viability of probiotic bacteria in dairy products.

On the other hand, by decreasing the fat content in frozen dairy

product formulations, quality characteristics on body and texture

are affected (Ohmes and others 1998). In this respect, inulin and

oligofructose, the best-knownprebiotics and also fat replacers, pos-sess several functional and nutritional properties that may be used

to formulate innovative healthy foods for today’s consumer. Inulin

is a term applied to a heterogeneous blend of fructose polymers

found widely distributed in nature as plant storage carbohydrates.

It has a degree of polymerization (DP) of 2 to 60. Oligofructose

is a subgroup of inulin, consisting of polymers within a DP ≤ 10.

Both inulin and oligofructose are widely used in functional foods

throughout the world (Sangeetha and others 2005). Their structure

is similar to corn sweeteners, principal carbohydrates used in ice

cream technology. Classed as fat replacers, inulin and oligofructose

influence the bulk and mouthfeel of the products. Also they are re-

sistant to hydrolysis in both the stomach and small intestine, and

are classified as dietary fiber ingredients (Spiegel and others 1994;Niness 1999).

The main uses of inulin and oligofructose are as texturizing

agents, particularly in low-fat foods such as ice cream (Devereux

andothers 2003).Some studies have been reported on thefunction-

ality of inulin as a fat replacer in reduced fat ice cream (Schaller-

Povolny and Smith 2001), in yog-ice cream (El-Nagar and oth-

ers 2002), and in fat-free starch-based dairy dessert (Tarrega and

Costell 2006). However, no research has been reported on both

functional andprebiotic effectsof inulinand oligofructose as a food

ingredient in low-fat probioticice cream. Thus, our objectivewas to

compare the effects of inulin or oligofructose supplementation es-

pecially on the survival of probiotic starter culture and also the rhe-

ological characteristics of low-fat probiotic ice cream. In addition,

M184 JOURNAL OF FOOD SCIENCE—Vol. 73, Nr. 4, 2008 C 2008 Institute of Food Technologistsdoi: 10.1111/j.1750-3841.2008.00728.xFurther reproduction without permission is prohibited




Probiotic culture survival in ice cream . . .

we aimed to compare the rheological characteristics of regular low-

fat ice cream and probiotic ice cream.

Materials and Methods

Ingredients and formulation for ice creamIn the production of ice cream, cow’s milk was supplied from

Ege Univ., Agricultural Faculty, Menemen Research Farm (Izmir,

Turkey), pasteurized cream containing 35% milk fat, and non-

fat milk powder was supplied from Pınar Dairy Industry (Izmir,Turkey), and freeze-dried DVS starter cultures of Lactobacillus

acidophilus La-5 and Bifidobacterium animalis subs. lactis Bb-

12 were obtained from Chr. Hansen Lab. (Hoersholm, Denmark).

Other ingredients for low-fat ice cream mix included sucrose and

corn syrup (G-40) (Cargill, Istanbul, Turkey), stabilizer–emulsifier

mixture of Cremodan SE 30 (Danisco AS, Copenhagen, Denmark),

inulin (Fibruline XL, molecular weight: 3300, degree of polymer-

ization > 20), and oligofructose (Fibrulose F97, molecular weight:

1000, degree of polymerization < 20) (Cosucra AS, Fontenoy, Bel-

gium).

Manufacture of ice cream

All ice creams were manufactured in the pilot plant of Dairy Technology Dept., Faculty of Agriculture, Univ. of Ege. Mix formu-

lation was 4% (w/w) milk fat, 12% (w/w) milk solids nonfat, 13%

(w/w) sucrose, 0.65% (w/w) stabilizer/emulsifier, 4% (w/w) 42 Dex-

trose Equivalent corn syrup for regular ice cream (R) and probiotic

ice cream (P), 4% (w/w) oligofructose for probiotic ice cream with

oligofructose (PO), and 4% (w/w) inulin for probiotic ice cream

with inulin (PI).

Raw milk and cream were weighed into stainless steel milk

cans. All dry ingredients were mixed into the cold liquid ingre-

dients and complete incorporation was ensured. The mixes were

pasteurized at 68 ◦C for 30 min. L. acidophilus La-5 and B. an-

imalis Bb-12 cultures were added to the mixes (0.3%) except for

the regular sample (R), after cooling to 40 ◦C, to achieve ap-

proximately 108 CFU/g, mixed well, and fermented for approx-

imately 4 h at 40 ◦C until the desired pH of 5.5 was reached.

Hekmat and McMahon (1992) reported that probiotic ice cream

was preferred at pH 5.5 regarding overall acceptance by judges.

The fermented mixes were then cooled in an ice bath to 5 ◦C.

All mixes were aged at 4 ◦C for 24 h to ensure complete hydra-

tion of all ingredients. Mixes were frozen in random order using

a batch ice cream freezer (4 L capacity, Ugur, Nazilli, Turkey) for

35 min. The ice cream was packaged into 150-mL plastic cups and

50-mL plastic cups (as 25 g for melting behavior), and then placed

in a hardening room at –18 ◦C. The experiment was conducted in

triplicate.

Compositional analysesTotal solids in the ice cream was determined by drying the sam-

ples for 3.5 h at 100 ◦C and fat contents were analyzed by means of

the Gerber method (AOAC 1990). The pH values of ice cream sam-

ples were measured with a pH-meter combined with a glass elec-

trode (Beckman Zeromatic SS-3, Beckman Instruments Inc., Fuller-

ton, Calif., U.S.A.). The titratable acidity in ice cream was deter-

mined with N /10 natrium hydroxide in the presence of phenolph-

thalein and expressed as percent lactic acid.

Rheological analysesOverrun was measured with a comparison of the weight of ice

cream mixture before and after freezing. The formula for overrun is

as follows:

Overrun% = (weight of ice cream mix) – (weight of ice cream)

× 100 × (weight of ice cream)−1 (Marshall and others 2003).

Apparent viscosities of the mixes were evaluated at 4 ◦C after

24 h aging using a Brookfield RVViscometer fitted with spindle no:5

at 20 rpm (Brookfield Engineering Laboratories, Stoughton, Mass.,

U.S.A.). Results were multiplied by RV viscometer factor (2000/N ,

N = 20 rpm) and given as Pa.s. Firmness of ice cream was de-

termined by a Surberlin PNR 6 Penetrometer (Sommer Runge KG,

Berlin, Germany). Penetrations of a conical spindle weighing 91.6

g (× 0.1 mm) to ice cream at –18 ◦C were measured after 5 s. Be-fore the measurements were taken, penetrations of the probe were

conducted 4 cm from the side of each cup and wererepeated twice.

Firmness wasmeasuredas thedepth(in mm)of penetration of con-

ical spindle into the ice cream and then a firmness index (g/mm)

was calculated by dividing the conical spindle weight (91.6 g) to the

depth of penetration (mm).

Melting behavior, expressed as 1st dripping time and melting

properties, was evaluated on ice cream samples stored at –18 ◦C.

Melting properties were determined by carefully cutting the plastic

cups from the ice cream samples (preweighed as 25 g), placing the

ice cream onto 1-mm stainless steel screen over a cup, and weigh-

ing the amount of ice cream drained into the cup over a 90-min

period at 20 ± 0.5 ◦

C. The time for the 1st drop of melted ice cream was also determined (Christiansen and others 1996).

Enumeration of probiotic bacteria The count of viable probiotic bacteria was determined after ag-

ing of the mix for 24 h at 4 ◦C, and then during the storage days of

the samples. One gram of probiotic ice cream sample was diluted

with 9 mL of sterile 0.1% (w/v) peptone water (Oxoid, Basingstoke,

Hampshire, U.K.) and mixed uniformly with a vortex mixer. Subse-

quent serial dilutions were made and viable cell numbers enumer-

ated using the pour plate technique. The counts of L. acidophilus

La-5 were enumerated on MRS agar (Merck, KGaA 64271, Darm-

stadt, Germany) incubated aerobically at 37 ◦C for 72 h. (Chris-

tiansen and others 1996). B. animalis Bb-12 was enumerated ac-

cording to the method of Lankaputhra and others (1996) using

MRS-NNLP (nalidixic acid, 15 mg/L; neomycin sulphate, 100 mg/L;

lithium chloride, 3 mg/L and paramomycin sulphate, 200 mg/L)

agar. Filter sterilized NNLP was added to the autoclaved MRS base

just before pouring (Laroia and Martin 1991). The inoculated plates

were incubated anaerobically at 37 ◦C for 72 h using an oxygen

free gas mixture of anaerobic jars (Merck). Plates containing 25 to

250 colonies were enumerated and recorded as logarithm of colony

forming units (CFU)/g of sample.

Statistical analysisEach experiment was independently replicated 3 times and all

analysis and enumerationswere done in duplicate. Analysis of vari-

ance for each set of data was conducted as a factorial arrangement

of treatments in a completely randomized block design to deter-

mine whether significant differences existed. For the storage ex-

periment, the set of data was conducted as a split plot in a ran-

domized complete block design. Each replication was a block; milk

treatment was the main unit treatment, and days of storage were

the subunit treatment. The model equation was Y ij k = µ+ αi +

β j(i) + δk + (αδ)ik + εi jk where µ, αi , β j (i ), δk , (αδ)ik , and εi jk repre-

sent overall mean effect, effect of milk treatment i , random ef-

fect of block j receiving milk treatment i , effect of storage time k ,

milk treatment by storage time interaction, and experimental error,

respectively.

Data were analyzed using the general linear model procedure of

the SPSS Win 9.0 program, and Duncan’s multiple range test was

Vol. 73, Nr. 4, 2008— JOURNAL OF FOOD SCIENCE M185





Table 1 --- Results (mean ± SD, n = 3) of compositional and physical analyses on aged mix and ice cream.

MixIce cream

Mix or Apparent viscosityice cream pH (Pa.s) Total solids (%) Fat (%) Lactic acid (%) pH Overrun (%)

R 6.90 ± 0.00b 1.76 ± 0.0a 33.38 ± 0.04a 4.0 ± 0.0a 0.14 ± 0.01a 6.90 ± 0.01b 23.6 ± 4.0a

P 5.52 ± 0.05a 2.68 ± 0.03b 33.42 ± 0.02a 4.0 ± 0.1a 0.51 ± 0.01b 5.45 ± 0.06a 27.6 ± 1.9ab

PO 5.52 ± 0.05a 3.35 ± 0.01c 33.47 ± 0.11a 4.1 ± 0.1a 0.51 ± 0.01b 5.45 ± 0.17a 31.7 ± 1.3b

PI 5.47 ± 0.05a 3.91 ± 0.04d 33.49 ± 0.05a 4.1 ± 0.1a 0.52 ± 0.02b 5.35 ± 0.17a 50.6 ± 2.5c

R = regular mix or ice cream; P = probiotic mix or ice cream; PO = probiotic mix or ice cream with oligofructose; PI = probiotic mix or ice cream with inulin.a,b,cMeans with different letters in the same column are different ( P < 0.05).

used to compare means when the effect was significant (P < 0.05).

In addition, statistical significance was given in terms of P values,

with differences at the 95% confidence interval (P < 0.05) being

considered statistically significant (SPSS 1997).

Results and Discussion

Compositional analyses of ice cream samples performed in the

1st day of storage revealed that the targeted total solids and

fat levels were achieved (Table 1). As expected, pH and lactic acid

contents of regular and probiotic ice cream samples were signif-

icantly different (P < 0.05) while similar lactic acid contents and

pH values were determined in all probiotic ice creams (P > 0.05).Regular ice cream sample had a mean pH value of 6.90 ± 0.01 and

lactic acid percentage of 0.14 ± 0.01. There were significant differ-

ences in viscosities among all mixes, including probiotic ice cream

mixes, and viscosity increased by addition of oligofructose or in-

ulin to mix (P < 0.05) (Table 1). High apparent viscosity in the

probiotic ice cream mix containing oligofructose or inulin can be

explained by the interactions of the dietary fiber and liquid com-

ponents of the probiotic ice cream mix. Ice cream mixes contain-

ing carbohydrate-based fat replacers exhibit a viscous behavior be-

cause of the capability for imbibing water, which would increase

the viscosity of the system (Schmidt and others 1993). The high-

est mean apparent viscosity of 3905 MPa.s (P < 0.05) was obtained

in the probiotic mixes containing inulin (Table 1). Similar to our

findings, significantly higher apparent viscosity was obtained by

replacing 100% of the 42 DE corn syrup with inulin in a reduced

fat ice cream mix (Schaller-Povolny and Smith 2001). The authors

reported that higher apparent viscosity resulted from the higher

molecular weight of inulin and that a potential interaction between

the inulin and milk proteins could also be present in the system.

Higher molecular weight of inulin may be related to higher ap-

parent viscosity of the ice cream mix with inulin in our study. In-

ulin, being highly hygroscopic, would bind water and form a gel-

like network that, in addition to other components (like corn syrup

or emulsifier–stabilizer mixture), would modify the rheology of the

mix. Similar results in relation to the effect of inulin on viscosity

were also reported by El-Nagar and others (2002) and Akın (2005)

for yog-ice cream and probiotic-fermented ice cream, respectively.

The highest overrun value was also obtained in probiotic ice

cream mix containing inulin (P < 0.05), indicating its responsibil-

ity for the increased air incorporation (Table 1). The overrun value

increased approximately 2 times when inulin was used in the man-

ufacture, in contrast to the findings of Akın (2005) for probiotic-

fermented ice creams. The addition of L. acidophilus La-5 and B.

animalis Bb-12 and fermentationof themix did notsignificantly af-

fect the overrun values (Table 1). Alamprese and others (2002) also

reported that Lactobacillus johnsonii La1 addition did not modify

the overrun of ice cream.

In the current study, a direct correlation has been determined

between firmness and melting behavior. Our results indicated that

all probiotic ice creams were found to be firmer than regular ice

Figure 1 --- Firmness index of ice cream during storage.R = regular ice cream; P = probiotic ice cream; PO =

probiotic ice cream with oligofructose; PI = probiotic icecream with inulin. The error bars represent the standarddeviation (n = 3). a,b,cMeans with different letters in thesame storage day are different (P < 0.05).

cream. Addition of oligofructose or inulin increased the firmness

in probiotic ice cream. (P < 0.05) (Figure 1). However, ice cream

supplemented with inulinwas significantly firmer than other prod-

ucts throughout the storage except the 1st day ( P < 0.05). Due to

its longer chain length, inulin is less soluble than oligofructose and

has the ability to form inulin microcrystals when sheared in wa-

ter or milk. These crystals interact to form a creamy texture (Niness

1999). In addition, the ability of inulin to bind water molecules and

form a particle gel network can improve the firmness of the prod-

uct (Franck 2002). Although it seems that firmness was improved in

all products by extension of storage, significant increases were not

found (P > 0.05) except for the 60th day for the P sample, the 60th

and 90th days for the PI sample, and the 90th day for the R and PO

samples.

A slower change in melting properties was observed in probi-

otic ice creams when compared to control sample during storage

(P < 0.05) (Figure 2). Melting properties were also improved by

using oligofructose and inulin (P < 0.05). However, the most re-

markable improvement in melting behavior was obtained in the

product containing inulin (P < 0.05). The change in melting prop-

erties decreased in all samples as storage time increased, and the

least change was obtained at the 60th and 90th days for the PI sam-

ple and the 90th day for the other products (P < 0.05). The 1st drip-

ping time was also longer in probiotic ice creams supplemented

with oligofructose and inulin in comparison to the control sample

(Figure 3). However, inulin increased the 1st dripping time more

than oligofructose, which was found to be statistically signif-

icant for all storage days (P < 0.05). Additionally, the times

prolonged in all samples as storage time increased while the

M186 JOURNAL OF FOOD SCIENCE—Vol. 73, Nr. 4, 2008





longest time was reported at the 60th and the 90th days for

the R, P, and PO samples and at the 90th day for the PI sam-

ple (P < 0.05). Typically, ice crystal size increases by about

30% to 40% during hardening of ice cream. In the storage, ice

recrystallization occurs. The small crystals melt at the same time

that large crystals grow. The changes in ice crystals due to the ther-

modynamic ripening process are enhanced by temperature fluctu-

ations. Small crystals, with a slightly lower melting point, are more

sensitive to temperature fluctuations than larger crystals (Marshall

and others 2003). Inulin or oligofructose can control ice recrystal-lization like a stabilizer agent. Therefore, the 1st dripping time of all

samples can be improved by these interactions as storage time in-

creased.Additionof inulinled to thelowest changein melting prop-

erties and longest 1st dripping time as well as the most increase

in firmness (P < 0.05), due probably to the high molecular weight

and hygroscopic properties of inulin. The gelling properties of in-

ulin improve the consistency of mix and retard the melting of the

Figure 2 --- Melting properties of ice cream during storage.R = regular ice cream; P = probiotic ice cream; PO =

probiotic ice cream with oligofructose; PI = probiotic icecream with inulin. The error bars represent the standarddeviation (n = 3). a,b,c,dMeans with different letters in thesame storage day are different (P < 0.05).

Figure 3 --- First dripping times of ice cream during stor-age. R = regular ice cream; P = probiotic ice cream; PO =

probiotic ice cream with oligofructose; PI = probiotic icecream with inulin. The error bars represent the standarddeviation (n = 3). a,b,cMeans with different letters in the

same storage day are different (P < 0.05).

product. These observations are consistent with those of El-Nagar

and others (2002) who demonstrated that inulin supplementation

reduced the melting rate and increased firmness in yog-ice cream.

Akın (2005) also reported that addition of inulin retarded the melt-

ing time of probiotic-fermented ice cream. This study has verified

that thehighest valuesfor theapparentviscosity, overrun,and firm-

ness and the most remarkable improvement in the meltdown char-

acteristics were obtained in the mix or ice cream containing probi-

otics and inulin (P < 0.05). Ice creams containing a high amount of

air (high overrun) tend to melt slowly. Air cells act as an insulator(Marshall and others 2003).

The viable counts of probiotic bacteria were 7.74 ± 0.51, 8.44 ±

0.16, and 8.24 ± 0.04 log CFU/g for L. acidophilus La-5 and 7.58 ±

0.62, 8.49 ± 0.14, and 8.12±0.28 log CFU/g for B . animalis Bb-12 in

the ice cream mixes P, PO, and PI, respectively. When compared to

the control sample, the viable counts for both L. acidophilus La-5

and B. animalis Bb-12 significantly increased in the probiotic ice

cream mix by addition of oligofructose (P < 0.05) due to the pos-

sible prebiotic effects of oligofructose in the ice cream mix. Fruc-

tooligosaccharides (FOS), especially oligofructose, are preferred by

bifidobacteria as a source of carbon and energy. Growth rates of bi-

fidobacteria cultivated on either oligofructose or inulin were eval-

uated and better growth was obtained on oligofructose than inulin(Wang and Gibson 1993; Gibson and Wang 1994). In addition, in

vitro fermentation of inulin revealed that molecules with a shorter

chain length are fermented quicker than molecules with a longer

chain length (Roberfroid and others 1998). Therefore, higher sur-

vival of these probiotics in ice cream mix containing oligofructose

can be sourced from shorter chain length or lower polymerization

degree of oligofructose than inulin.

The changes in the viable counts of L. acidophilus La-5 and B.

animalis Bb-12 in ice cream samples during storage are presented

inTable 2. During freezing of the mix, the counts of both viable bac-

teria decreased by 1.5 to 2.0 log units, and their numbers in the

frozen ice cream were found to be in the range of 5.96 to 6.60 log

CFU/g for B. animalis Bb-12 and 5.98 to 6.21 log CFU/g for L. aci-

dophilus La-5. The decline in bacterial counts, as a result of freez-

ing, is most likely due to the freeze injury of cells leading eventually

the death of cells. Furthermore, the incorporation of oxygen into

the mix may have resulted in an additional decrease in viable cell

counts as well as the mechanical stresses of the mixing and freez-

ing process. The counts also significantly decreased (0.3 to 0.9 log

CFU/g) throughout the storage (P < 0.05); however, freezing and

mixing involved in converting the mix into ice cream had a greater

effect on culture viability than storage in ice cream (P < 0.05). A

similar finding was reported by Hagen and Narvhus (1999), Alam-

prese and others (2002), and Haynes and Playne (2002), but not by

Hekmat and McMahon (1992). During freezing and storage of ice

cream, more or less reduction in the survival of probiotic bacte-

ria was also reported (Hekmat and McMahon 1992; Christiansen

and others 1996; Hagen and Narvhus 1999) for different microor-

ganisms, different production technologies and formulations, and

pH. On the other hand, Davidson and others (2000) and Alamprese

and others (2002) reported that starter culture bacteria in low-fat

ice cream did not change significantly during storage.

In our study, B. animalis Bb-12 survived better than L. aci-

dophilus La-5 in ice cream over 90 d (Table 2). However, the viable

counts of B. animalis Bb-12 were higher than the recommended

minimum limit of 106 CFU/g only in ice cream containing

oligofructose during storage. In addition, according to the general

mean value of storage, the ice cream products supplemented with

oligofructose contained higher viable counts of both probiotic bac-

teria during the storage, possibly depending on the higher viable

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Table 2 --- Viable counts of L. ac i d o p hil us La-5 and B. an i ma li s Bb 12 (mean ± SD, n = 3) in ice cream during storage(log CFU/g).

Ice cream 1st day 30th day 60th day 90th day Mean of storage

L. acidophilus La-5P 5.98 ± 0.25aB 5.53 ± 0.18aAB 5.02 ± 0.48aA 5.13 ± 0.28aA 5.41 ± 0.48a

PO 6.21 ± 0.02aB 5.77 ± 0.11bA 5.79 ± 0.15bA 5.70 ± 0.10bA 5.87 ± 0.23b

PI 6.00 ± 0.09aB 5.47 ± 0.14aA 5.24 ± 0.10aA 5.12 ± 0.46aA 5.46 ± 0.41a

B. animalis Bb-12P 6.27 ± 0.19bB 5.97 ± 0.07bA 5.93 ± 0.26bA 5.94 ± 0.20abA 6.03 ± 0.23b

PO 6.60 ± 0.20cB 6.40 ± 0.17cAB 6.45 ± 0.28cAB 6.25 ± 0.11bA 6.43 ± 0.22c

PI 5.96 ± 0.13aB 5.36 ± 0.35aA 5.51 ± 0.19aAB 5.47 ± 0.55aAB 5.57 ± 0.39a

P = probiotic ice cream; PO = probiotic ice cream with oligofructose; PI = probiotic ice cream with inulin.a,b,cMeans with different letters in the same column are different ( P < 0.05).A – CMeans in the same row with different superscripts are significantly different (P < 0.05).

countsin mixes with oligofructoseand more conducivestructureof

oligofructose to cell viability during storage (P < 0.05). The lowest

viable counts of B. animalis Bb-12 obtained in the products with

inulin in the first and other days of storage (P < 0.05) can be caused

by the higher overrun rate of these samples (Table 2). In general,

being strictly anaerobic, Bifidobacterium spp. are more sensitive

to oxygen than L. acidophilus (Talwalkar and Kallasapathy 2003).

Conclusions

The best improvement in textural characteristics in terms of

firmness, melting properties, and 1st dripping time was ob-

tained in probiotic ice cream with inulin during storage (P < 0.05).

Viable starter culture counts reduced (0.3 to 0.9 log CFU/g) during

thestorage, butat theinitial freezingand churning stage of convert-

ing mix into ice cream a greater decrease (1.5 to 2.0 log unit) in the

counts L. acidophilus La-5and B. animalis Bb-12 (P < 0.05) was ob-

served. Survival of L. acidophilus La-5 and B. animalis Bb-12 in ice

cream was significantly enhanced with oligofructose (P < 0.05) and

the recommended minimum limit of 106 CFU/g was maintained

for B. animalis Bb-12 in only probiotic ice cream with oligofructose

during storage.

AcknowledgmentsThe authors thank the Ege Univ., Faculty of Agriculture, and Re-

search Fund Council for financial support to this study.

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