01 emerging technologies and food packaging

FSFB, 3rd International Congress, 14-17 October, 2008, Querétaro

187

ET-02

Effect of pH and Temperature on the Release of Nisin from Antimicrobial Edible

Whey Protein Isolate-based Films with Different Thicknesses

Rossi-Márquez, G., Han, J.H., García-Almendárez, B., Castaño-Tostado, E., Regalado-González, C.

1,2Departamento de Investigación y Posgrado en Alimentos, Facultad de Química. Universidad Autónoma

de Querétaro, CU, Cerro de las Campanas s/n Col. las Campanas. Querétaro 76010 Qro.

[email protected], [email protected]

2

Nowadays there is a worldwide concern about the environment and researchers are trying

to design new natural packaging materials for food products as a contribution to reduce

pollution. WPI edible films have been produced recently with this aim. The objective of

this study was to produce a whey protein edible film with an antimicrobial agent (nisin)

and to evaluate the migration of this substance at different temperatures, pH and film

thicknesses. Nisin is a bacteriocin produced by Lactococcus lactis subsp. lactis, which is

able to inhibit gram-positive microorganisms. The film was placed in a solution at

different temperatures (5-10°C) and pH´s (4-7). A sample was taken and later, the effect

of these factors on the release of nisin was determined. Nisin diffusion was determined

using Fick´s second law solution. An optimum Bayesian statistical design was used. The

release of nisin was favored at low pH´s. A tendency to release more nisin occurred with

the films with less thickness. Temperature did not have a significant effect on nisin

release. The tensile strength and the elastic modulus were not affected by the film

thickness. The opposite occurred for elongation, because a more stretchable matrix was

formed in thicker films. This enabled a greater cross sectional area permitting greater

extension under stress than the thinner films. The water vapor permeability (WVP) was

not significantly affected by the different thicknesses. Larger diffusivity occurred with

neutral pH and at higher thicknesses, because this treatment used a higher temperature,

and this favors molecular motion, increasing the diffusivity of nisin. On the basis of these

results, the films evaluated had good mechanical properties. At acid pH and low

thicknesses nisin release to the solution was significantly higher.

(key words: whey protein isolate (WPI), mechanical properties, water vapour

permeability, diffusivity.)


188

ET-03

Preparation of Fresh-cut Jack Fruit (Artocarpus heterophyllus Lam) Stored in a

Passive Modified Atmosphere

Ulloa, S.A., Montalvo, G. E., García, H.S., Mata, M.M. and Tovar, G.B.

1Laboratorio Integral de Investigación en Alimentos, Instituto Tecnológico de Tepic. Av. Tecnológico

2595. Tepic, Nayarit. Tel. y Fax: 52(311) 211-94-00. México. 2UNIDA, Instituto Tecnológico de Veracruz, M.A. de Quevedo 2779, Veracruz, Ver. 91897, México.

*Corresponding Author. e-mail: [email protected].

Jack fruit is produced in the state of Nayarit and has experienced a increasing commercial

importance for both domestic as well as foreign markets. However, it has a short shelf

life, and it is difficult to handle. In this study several variables and their interactions were

evaluated so that pre-cut Jack fruit could retain its sensory quality and an extended shelf

life. On Stage 1 we determined the interactions of six factors: the type of segment cutting

(whole and half), segment color (yellow and orange), maturity stage (during consumption

and before consumption), antioxidant use (with and without 0.1% isoascorbic acid; with

and without 0.1 % methyl jasmonate; and with and without 0.5% calcium chloride).

Treated fruits were stored at 5 °C for 7 days, using a 26-3

fractional factorial design. On

Stage 2, we evaluated piercing or not of the packaging (low density polyethylene), kept at

5 and 10 °C, and stored for 7 and 14 days, respectively. Firmness, pH values, acidity,

flesh color, total soluble solids, the respiratory rate (RR) measured as the production of

CO2 and the reduction of O2, ethylene production rate, sensory evaluation (flavor, color

and aroma), total aerobic count, mold and yeast counts were monitored. For Stage 1, the

RR of segments in maturity stage prior to consumption had a clear climacteric peak

between 2 and 3 days after cutting, while fruit segments in the consumption stage of

maturity, the RR decreased with time. The CO2 produced, ethylene production rate, and

O2 consumption remained constant 72 hours after been packaged. According to the

sensory evaluation data and compositional parameters, it was decided that the most

suitable handling conditions in the first stage were half segments, orange colored, at

consumption stage of maturity, with added methyl jasmonate, with added antioxidant and

without calcium. For Stage 2, CO2 production, ethylene production rate and O2

consumption in the fruits packaged without piercing reached its stability between 4 and 5

days, while in perforated bags, CO2 and ethylene concentrations were reduced. According

to the sensory evaluation, physiochemical parameters and microbiological tests, we found

the best sensory characteristics in the pre-cut fruits stored for 7 days at 5 ºC in the intact

bags.

(keywords: Artocarpus heterophyllus lam, fresh-cut Jack fruit, sensory evaluation)


189

ET-04

Degradation Kinetics upon Storage of Blackberry Anthocyanins Extracts Processed

by High Hydrostatic Pressure and Thermal Treatment

Ramirez-Leon L, Torres J.A, Mercado-Silva E.

1Universidad Autónoma de Querétaro; Facultad de Química. Centro Universitario Cerro de las Campanas

S/N. CP 76010. Querétaro, México. Department Food Science and Technol. Oregon State University. 100

Wiegand Hall Corvallis, OR 97331. USA. E-mail: [email protected]

Extracts of blackberry anthocyanins were treated by high hydrostatic pressure (HHP, 85

Kpsi/3 min) and pasteurization (63-65°C/30s) to stabilize them and the storage stabilities

were evaluated over temperature range 4-45 °C, with pH´s between 1-4 and in

presence/absence of light. The results showed that there was no effect of HHP or

pasteurization methods. However, the anthocyanins showed a more rapid degradation

with the increase in temperature during storage, (after 40 days and pH 1, the retention of

these pigments was 89 and 6% at 4 and 45ºC respectively) following a first-order

kinetics. On the other hand, the low pH's improved anthocyanins stability (after 90 days

and 4ºC the retention percent was 79 and 34% at pH 1 and 4 respectively); whereas at

low temperatures and pH 1, the light decreased moderately the pigment retention (85 and

73% without and with light) but at 45ºC the loss of these pigments was very high

independently of the presence of light. The reaction kinetics as a function of temperature

was described by the Arrhenius equation. Anthocyanins extracts at pH 4.0 in presence of

light were less stable than those at pH 1.0 without light, where activation energies ranged

from 6.65-15.31 kcal/ mol, respectively.

(keywords: anthocyanins extracts, blackberry, high hydrostatic pressure, degradation

kinetics)


190

ET-05

Effect of Conditions in Osmotic Dehydration of Chayote (Sechium edule) Using

Taguchi Methodology

Jiménez-Vieyra, M.E., Zambrano-Zaragoza, M.L., Rosas-Ortiz, L., S., Almaguer-Tellez, L..

1Escuela Superior de Ingeniería Química e Industrias Extractivas, Instituto Politécnico Nacional. Unidad

Profesional Adolfo López Mateos, edificio 7, Zacatenco, México D. F., C. P. 07738, México,

[email protected]. 2Departamento de Ingeniería y Tecnología, Facultad de Estudios Superiores Cuautitlán, Universidad

Nacional Autónoma de México. Av. 1o de mayo s/n, Cuautitlán Izcalli, Edo. Méx., C. P. 54715, México,

[email protected].

The chayote (Sechium edule) belongs to the Cucurbitaceae family and is native from

Mexico and Central America. It has a high starch, fiber and minerals content. An

alternative preserving method is the osmotic dehydration that decreases energy costs

incurred in traditional drying techniques. It is necessary to subject vegetables to

blanching treatments before the osmotic dehydration. This work evaluates the effect of

the blanching method, the osmotic solute concentration, the temperature, the total solids

contents on the diffusion coefficients. A Taguchi L827 design with three factors was

employed using Xanthan gum as coating. The washed and peeled chayotes were sliced in

2.0x1.0x0.5 cm cubes and blanched by boiled water or microwaves. After the thermal

treatment, the samples where dehydrated in 1:2 osmotic solution at 40 or 55 oBx and

filtered at 25 or 35 oC. According to the proposed experimental design, the diffusion

kinetic of the osmotic agent was obtained to evaluate the mass loss and the variation in oBx for the samples and the solution. Every experiment was done in triplicate and the

results were analyzed using MINITAB 14 statistical software. The results showed that the

osmotic solution concentration the greatest effect on the diffusion coefficients and the

mass kinetic diffusion. The microwave energy increased the diffusion of the osmotic

agent from the samples to the solution; the mean of the diffusion coefficients was 8.2x10-

8 m

2/s for samples immersed in 40

oBx solution, and 2.9x10

-7 m

2/s for samples in 55

oBx

solution. The kinetic constants for the osmotic agent diffusion from the solution to the

chayote samples were 0.23 g/h of soluble solid for samples in 40 oBx solution, and 0.21

g/h for samples in 55 oBx. It was established that the temperature had greater influence

compared to the change in permeability of the samples as an effect of the pretreatment

with kinetic constants of 1.23 g/h at 40 oBx and 0.085 g/h at 55

oBx. The results suggest

the importance in the use of microwave energy as a factor in the variation of the diffusion

velocity of the osmotic agent.

(key words: chayote, osmotic-dehydration, xanthan gum, kinetic-constants)


191

ET-06

Carotenoids and xanthophylls variations in Passion Fruit (Passiflora edulis) treated

with microwaves

Jiménez-Vieyra, M.E., Zambrano-Zaragoza, M.L., Naranjo-Martínez, A., Torres-Calderón, J.

1Escuela Superior de Ingeniería Química e Industrias Extractivas, Instituto Politécnico Nacional. Unidad

Profesional Adolfo López Mateos, edificio 7, Zacatenco, México D. F., C. P. 07738, México,

[email protected]. 2Departamento de Ingeniería y Tecnología, Facultad de Estudios Superiores Cuautitlán, Universidad

Nacional Autónoma de México. Av. 1o de mayo s/n, Cuautitlán Izcalli, Edo. Méx., C. P. 54715, México,

[email protected].

Carotenoids and xanthophylls are somewhat resilient to extreme heat and pH. However,

these agents may cause partial cis-trans transformation of certain double bonded links

that could modify color and nutritional value. Moreover, carotenoids and xanthophylls

are very sensitive to oxidation with light, lipoxidases and lipid peroxides, responsible for

discoloration of some vegetables. The objective of this work was to measure the effect of

microwave blanching treatment in terms of carotenoids and xanthophylls variations in

Passion Fruits. Purée samples of the fruit were treated with microwave energy from 2 to

16 s; carotenoids and xanthophylls were extracted and their absorption coefficients were

measured by spectroscopy. The peak absorptions for carotenoids and xanthophylls in

Passion Fruits were 434 and 474 nm, and they increased with treatment time. Thus,

carotenoids and xanthophylls were preserved and stabilized when exposed up to 10 s of

treatment without sample deterioration. This work suggests that the color stability in

fruits can be enhanced by microwave treatment.

(keywords: passion-fruit, blanching, carotenoids, xanthophylls)


192

ET-07

Effect of Irradiation on Microbial Population and Lipid Oxidation

in Pork Meat

Acuña-Duarte, B. I., Cornejo-Ramírez, Y. I., Domínguez-Salazar, M. F., Falcón-Villa, M. R.,

Melendrez- Amavizca, R., Pérez-López E. J., Robles-Figueroa, P.

Departamento de Ciencias Químico-Biológicas, Universidad de Sonora. Col. Centro, 83000 Sonora

[email protected], *[email protected]

Three pork meat lots were analyzed with the purpose of observing the effect of

irradiation on the microbial population, and on lipid oxidation. The three batches were

treated differently: the first batch was irradiated with 60

Co in a dose of 1 kGy and was

packed in an oxygen impermeable polyethylene film; the second batch was vacuum

packed in the same film, and the third batch was covered with a semipermeable film,

only. Every batch comprised five packages containing 100 g of meat each one, and

were stored at 10º C. The free fatty acids and peroxide index were determined as a

measurement of their oxidation. In addition, pH and color were also determined, to

monitor the physical changes that occurred throughout the storage time. Microbial

total count was determined as a measure of spoilage extent. Every determination was

performed in triplicate after 0, 1, 3, 13, 24, and 30 d. Results showed that irradiation

reduced microbial population in meat compared with other conventional conservation

methods, resulting in an extended meat stability and shelf life. The irradiated batch on

the 24th

day showed 7,850 UFC/g, whereas the second batch showed 90,000 UFC/g,

and the third batch 673,300 UFC/g. Nevertheless, irradiation increased fat oxidation,

which was more noticeable in the semi-permeable film (third batch). The peroxide

index was 55 meq/kg for the irradiated batch, 23 meq/kg for the vacuum packed meat,

and 60 meq/kg for the third meat batch. Therefore, batches 1 and 3 showed a greater

fat oxidation than batch 2 (vacuum packed).

(keywords: pork meat, irradiation, packaging, lipid oxidation, microorganism total

count)


193

ET-08

Effect of a Sodium Caseinate Edible Coating on the Physicochemical and Textural

Properties of a Blackberry (R. ulmifolius) and Berry cactus Fruit (M. geometrizans)

Correa-Betanzo, J., Arredondo-Ochoa, T., Santoyo-Angel, C.J., Zurita-Olvera, L., Pérez-Pérez, C.I.

Departamento de Ingeniería Bioquímica. Instituto Tecnológico de Celaya. Av. Tecnológico y Antonio

García Cubas s/n. Col. FOVISSSTE. Celaya 38010, Guanajuato. [email protected];

*[email protected]

Evidence suggests that edible soft-fleshed small fruits classified as berries have very

short postharvest life as a result of textural changes during transportation and storage.

The aim of this research was to evaluate the effect of a sodium caseinate (Na-Cas)

based edible coating plastified with sorbitol (S) and glycerol (G) on the

physicochemical and textural properties of blackberries and berrycactus fruits.

Control (C), Na-Cas(S) and Na-Cas(G) fruits were packed in clam-shell boxes and

stored at 5º C and approximately 50% RH for 1 week. Weight loss, pH, tritable

acidity (TA), soluble solids (SS), chroma (C*), hue degrees (ºh) and texture profile

parameters were evaluated daily. Physicochemical results indicated that significant

differences (p < 0.05) were observed in weight loss between control and coated

samples, whilst non-significant differences were detected on pH, TA, SS, C* and º hue

among all the samples. Texture profile analysis showed a decrease in fruits firmness,

cohesiveness, springiness, resilience, and chewiness, whereas adhesiveness decreased

as storage time increased. Adhesiveness and cohesiveness were affected mainly by

storage temperature, whereas chewiness and resilience were affected by coating.

Nonetheless, coating treatment improved mechanical properties of the fruits during

storage. Hence, sodium caseinate based coatings can be used as a natural coating on

fresh berries to control weight loss, thus improving appearance and mechanical

properties of the fruits for a longer time interval.

(keywords: blackberry (Rubus ulmifolius), berrycactus fruit (Myrtillocactus gemetrizans),

edible coating, texture profile analysis)


194

ET-09

Developing an Edible Film Based on Biopolymers for Conservation of Meat

Products

Romero-Lopez, K.; Castillón-Jardón, J.; Perez-Alonso, C.

Facultad de Química, Universidad Autónoma del Estado de Mexico, Paseo Tollocan esq. Paseo Colón S/N,

Toluca, Edo. de Mex., 50120, México, phone: (+52)7222965541, fax: (+52)7222965514

[email protected] ; [email protected] ; [email protected]

An edible pack is described as an integral part of the food and consumed as such.

Because of this dual function, packaging and food constituent, edible coatings offer many

advantages, but also must meet certain conditions specified in the standard of

workmanship. The edible coatings are known for their implementation in fresh fruits,

because this packaging system helps prevent the oxidation of these, but can also fill this

role in nuts, some meat or fish. The main objective of this work was to develop an edible

coating that functions as a preservative and as a vehicle for cooked meat. In the formation

of the film we used a combination of mesquite gum, sodium carboxymethylcellulose and

whey protein, to have a synergy of properties. Although these materials have similar

physical and chemical properties, they complement each other to improve functionality,

while allowing the use this film as a vehicle for condiments in the cooked products. The

film was produced by a dry mixture of biopolymers which were then dispersed in cold

water, and after homogenization hot water was added to complete dissolution of the

ingredients. pH and density of this mixture was tested. Then the meat was covered with

the mixture, and pH and texture were determined. To evaluate the efficiency of the film,

analysis was performed using the texture EZtest Rheomether, which allowed us to

determine the change in texture of the meat covered with the film over a period of time.

The texture measurements were made from raw meat, until the fourth week in freezing,

thus making a comparison that determined that the film actually helps in the conservation

of the texture of the meat. Likewise took place a simple sensory analysis to determine

whether the film was to the liking of consumers, obtaining a favorable result.

(keywords: biopolymers, edible coatings, vehicle, texture)


195

ET-10

Development of a Linseed-Mucilage Edible Coating and its Application to Extend

Fresh-cut Cucumber Shelf-life

Hernández Lozano, L. C.; Pérez-Cabrera, L. E. & González-Martínez, C.

(1)Posgrado en Ciencias y Tecnologías Agrícolas, Pecuarias y de los Alimentos Centro de Ciencias

Agropecuarias, 20900 Jesús María, Aguascalientes, México. (2)

Universidad Autónoma de Aguascalientes,

Departamento de Tecnología de Alimentos. 20900 Jesús María, Aguascalientes, México. (3)

Universidad

Politécnica de Valencia, Departamento de Tecnología de Alimentos. 46022 Valencia, España

[email protected] (*)(2)

[email protected]

The increment on consumer demands of high quality foods and the concern of

environment deterioration have forced the food processors to reduce disposable

packaging waste and have led to increase research interest on edible films and coatings.

In this work, the application of linseed mucilage (Linum usitatissimum) was investigated

as an edible coating to extend the shelf-life of fresh-cut cucumber. Fresh-cut quality was

evaluated by weight loss, firmness retention, visible decay, development of surface color,

titratable acidity, total soluble solids, respiration rate CO2/O2, microbial growth and

sensory evaluation. The coating of linseed mucilage–based with carboxymethyl cellulose

(CMC), citric pectin (CP), propylene glycol (PG), glycerin (G) and calcium disodium

ethylene diamine tetra acetate (EDTA) in aqueous medium had a significant effect on

firmness retention and weight loss. It also showed better physico-chemical results

compared to the control fresh-cut cucumber. Sensory evaluation of the fresh-cut

cucumber showed that the composite coating kept the visual quality of the cucumber

during the storage time. Coating application did not significantly reduce microbial growth

in fresh-cut cucumber.

(keywords: linseed mucilage; edible coatings; fresh-cut; cucumber, storage)


196

ET-11

Study of Mechanical Properties and Repellents Against Rhizopertha dominica of

Pure and Composed Chitosan Films

Cota-Arriola, O.; Cortez-Rocha, M.O.; Castillo-Ortega, M.M.; Parra-Vergara, N.V. and Plascencia-

Jatomea, M.

University of Sonora. Food Postgrade and Research Department. Polymers and Materials Research

Department. Blvd. Luis Encinas & Rosales s/n. Col. Centro

Hermosillo, Sonora. C.P. 83000. E-mail: [email protected]

There is an increase interest to obtain biodegradable films. The chitosan is a lineal

cationic polysaccharide commercially obtained from chitin deacetylation extracted from

of crustaceans‟ shells, which present filmogenic properties, besides of being

biodegradable and nontoxic. The objective of this research is to evaluate the mechanic

properties of chitosan biofilms and their repellent activity against insects. This research

used commercial chitosans of low, medium and high viscosity, as well as chitosans

obtained from shrimp waste by chemical and biological extraction methods, which were

characterized by their molecular weight (100-800 KDa) and deacetylation degree (80-

91%). Films from each polymer were made using the casting technique, and their

mechanic properties were determinate by measuring the films deformation (ASTM D882-

91) and the repellence activity against the primary insect Rhizopertha dominica, using the

free choice test. Generally, the obtained films resulted to be clear and homogenous,

noticing better elastic properties by the addition of plasticizer. Comparing with the

commercial cellophane control (7.8% deformation & 100 MPa strain of strength), the

pure films resulted to be fragile and nonflexible, whose mechanic properties of effort-

deformation were: 2.98 to 4.83% and the strain of strength 53.08 to 83.23 MPa. In the

other hand, when adding the plasticizer were observed values of 10 to 22% deformation

and the strain of strength 20 to 40 MPa. According to empirical observations, chitosan

films obtained for each biological treatment presented more repellent activity versus R.

dominica. Thus, the higher mortality index (35% to 96 h) was observed in chitosan films

obtained by chemical processing. In conclusion, the chitosan films present a promising

alternative to be used like packing materials due to their functional properties

(antimicrobial activity and insect repellent), moreover its affinity and compatibility with

different substances that allow improving their mechanical properties.

(keywords: chitosan, Rhizopertha dominica, mechanical properties).


197

ET-12

Panela Cheese Elaborated With High-Pressure Homogenized Milk

Ruiz-Espinosa, H.*, Martínez-Valencia B.

, Arellanes-Lozada, P.

, Amador-Espejo, G.

y Welti-Chanes, J.

*Colegio de Ingeniería en Alimentos Facultad de Ingeniería Química. Benemérita Universidad Autónoma

de Puebla,CU 18 sur y Av. San Claudio San Manuel. Puebla, 72570

[email protected]

Pasteurization is the most common heat treatment used to eliminate pathogens and most

of the spoilage flora in milk. Nevertheless, this process brings some important

physicochemical, rheological, microstructural and sensory changes in the fluid milk

properties and, consequently, in some dairy products, like cheese. Several non-thermal

processes have been proposed as an alternative to achieve the same level of microbial

safety without compromising functional and sensory characteristics in milk. Among

these, high-pressure homogenization (HPH) is a state-of-the-art technology with potential

applications in dairy processing. Microbial inactivation, modifications in enzyme activity,

fat globule size reduction, and casein-whey protein interactions in HPH milk have been

observed. Yield increase and changes in functional characteristics of selected cheese

varieties have also been reported. To date there has not been any published research

addressing the use of HPH milk on the manufacture of fresh-like cheese. The aim of this

work was obtaining HPH milk with acceptable microbiological quality and suitable

cheesemaking properties for the manufacture of Panela cheese. Milk was HPH-processed

at 50, 150, 200 and 250 MPa in a Stansted Hydrive nG7400:350 homogenizer using an

inlet temperature of 20°C. Pasteurized milk (PM) (72°C, 15 s) was used as a control.

Milk samples (40 mL) were taken after each treatment to assess total bacteria count

(TBC) reduction. Panela cheese was manufactured using a standardized bench-top scale

make procedure. Yield, texture profile, and color were determined in all cheeses at day 1

while visual appearance was followed during 30 days of refrigerated storage. Increasing

the pressure led to lower bacterial counts; however, only milk treated at 250 MPa was

comparable to PM in terms of microbial inactivation. Although greater yields were

observed with higher pressure, hardness and cohesiveness decreased, leading to cheeses

that tended to loose structure during storage; besides, all cheeses exhibited abundant

syneresis. Better processing conditions must be found in order to obtain safer cheeses

while minimizing functional and sensory properties.

(keywords: high pressure homogenization, milk, panela cheese, non-thermal processing.)


198

ET-13

Effect of Modified Atmosphere Packaging on Functional Properties of

Pomegranate Arils (Punica granatum L)

Almonte-Flores D.C., Avelar-Meráz C., Ramírez-Solís C., Valenzuela-Gurrola , Ochoa-Martínez, L.A.

Morales-Castro J.

Posgrado en Ingeniería Bioquímica. Instituto Tecnológico de Durango.Blvd. Felipe Pescador 1830 Ote.

C.P. 34080 Tel. (618) 818-5402 y 818-6936 [email protected]; juliana@itdposgrado-

bioquimica.com.mx

The functional and physical chemicals properties of whole pomegranate arils (Punica

granatum cv. wonderful) ready to eat were evaluated after modified atmosphere

packaging to two storage temperatures (4 and 8 °C) in two different kinds of package

giving four treatments. The kinds of package were sealed plastic films and plastic

recipients. The arils were extracted manually and washed with a chloride solution

(100µL/L) during two minutes at 5 °C in order to be packed on an aseptic way. The

measurements were made during 20 days using one package (with 100 g of arils) of each

treatment every four days. The pH, total soluble solids (TSS) and color (L, a and b) were

measured in order to evaluate the physical chemicals properties. The total phenolic

compounds content (TPCC) and the antioxidant activity were determinated in order to

evaluate the functional properties. The measurements showed an increase in the pH and

the TSS, and a decay in the TPCC and in the antioxidant activity for the four treatments.

The packed arils on sealed plastic films and stored at 4 °C resulted the best because the

functional properties decay was lower.

(keywords: pomegranate, postharvest treatments, antioxidant activity)


199

ET-14

Decreasse in Respiratory Rate and Enzymatic Activity in Cantaloupe Melon

(Cucumis melo) Hydrocooled and Covered with a HPMC-Paraffin Film

Meza Velázquez, Jorge.Armand, Esparza Rivera, Juan Ramón, Alanís Guzmán, Guadalupe. Ramírez Baca,

Patricia ; Reyes Avalos, Concepción; Minjares Fuentes, José Rafael.

1Facultad de Ciencias Químicas, Universidad Juárez del Estado de Durango1 Gómez Palacio, Durango;

2Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León.

[email protected]

It was evaluated the effect of the application of a polymeric film based on

hydroxipropilmethylcelulose (HPMC) and paraffin on the respiratory rate and enzymatic

activity of hydrocooled Cantaloupe melon. Experimental samples (entire melon) were

either untreated (CONTROL) or treated. Treatment (HPMC-PAR) consisted in

hydrocooling the samples by immersing them in cold water (5 oC) for 20 minutes, and

afterward covered with a HPMC-paraffin film and stored at 8oC for up to 20 days.

Samples were analyzed at 0, 4, 8, 12, 16 and 20 days of storage. Analytical tests were:

weight loss, chilling injury, instrumental texture (external and internal), titratable acidity,

pH, and measurements of respiratory rate (CO2 production and quantification of internal

CO2), enzymatic activity (pectinmethylesterase and lipase activity), and quantification of

volatile compounds. Covered melons had lower titratable acidity and weight loss (P <

0.05), but higher values in texture, internal CO2, lipase enzymatic activity, and

concentration of volatile compounds (P < 0.05). On the other hand, there was no

significant difference in oBrix and CO2 production between treatments (P > 0.05).

Application of hydrocooling had no significant effect over the measured variables.

Obtained results suggest that the application of HPMC-paraffin films may extend shelf

life of entire Cantaloupe melon.

(keywords: cantaloupe melon, hydroxypropylmethylcelulose, hydrocooling)


200

ET-15

Effect of Sanitization on the Antioxidant Capacity of Fresh-Cut Jalapeño Peppers

Martínez, A., Ruiz-Cruz, S, Rodrigo-García, J., de la Rosa, L. A., González-Aguilar, G. A.

3, Alvarez-

Parrilla, E. 1Universidad Autónoma de Ciudad Juárez, Instituto de Ciencias Biomédicas, Departamento de Ciencias

Básicas, Ciudad Juárez, Chihuahua, México. 2Centro de Investigación en Alimentación y Desarrollo, A. C.,

Unidad Delicias. 3Centro de Investigación en Alimentación y Desarrollo, A. C., Dirección de Tecnología de

Alimentos de Origen Vegetal. *e-mail: [email protected]

The consumption of fresh-cut fruits and vegetables has increased during the last decade,

as a consequence of lifestyles change and epidemiological evidence that correlate a

regular intake of fresh fruits and vegetables with a reduced risk of developing several

chronic and degenerative diseases. Fresh-cut produce faster deterioration than that for

intact products, because they are wounded during the process. For this reason, a

sanitization treatment has to be applied to the final product in order to reduce this

problem. However, the number of studies in which the effect of the sanitization process

on the nutrimental quality of the produce is analyzed is scarce. The aim of the present

work was to evaluate the use of different sanitizers on the total phenol concentration and

antioxidant capacity of fresh-cut Jalapeño Peppers. Fresh-cut Jalapeño peppers were

treated with four sanitizers: sodium hypochlorite, peroxiacetic acid, acidified sodium

chlorite and carvacrol. At 3 day intervals, samples were evaluated for ascorbic acid (AA,

HPLC method expressed as mg AA/100 g FW), phenols (Folin-Ciocalteu method,

expressed as Gallic Acid Equivalents/100 g FW) and antioxidant capacity (FRAP

method, expressed as mmol Fe2+

/100 g FW). Initial values of ascorbic acid, total phenols

and antioxidant capacity were 90 mg AA/100 g FW, 12-24 mg GAE/100 g FW and 490-

1090 mmol Fe2+

/100 g FW, respectively. Carvacrol treated peppers showed the highest

total phenol and antioxidant capacity, due to impregnation of the phenol compound.

Good correlation between phenols and FRAP values were observed, suggesting that

phenols are the main contributors to antioxidant capacity in Jalapeño Peppers. All

sanitizers effectively maintained microbiological and overall quality of Jalapeño Peppers

during 26 days, except Carvacrol (17 days). At the end of the storage period, all

treatments showed a decrease of 12 to 43% respect to the initial value in vitamin C, total

phenols and antioxidant capacity. These results suggest that nutrimental quality should

also be evaluated when shelf life of fresh-cut produce is determined.

(keywords: jalapeño pepper, antioxidant capacity, sanitization, total phenols, FRAP)


201

ET-16

Study of Basic Mechanicals Properties of Wheat Kernels Using the Compression

Load and Ultrasonic Methods

Ponce, G. N. (1), Figueroa, C. J.D.* (2), Muñoz, S. J. (2), Camacho, R. R. (1), Martínez, H.E. (3),

Ramírez, W. B. (4)

(1) Departamento de Investigación y Posgrado en Alimentos, Facultad de Química. Universidad

Autónoma de Querétaro. Cerro de las Campanas S/N, Querétaro, Qro., CP 76010. (2) Centro de

Investigación y de Estudios Avanzados (CINVESTAV-IPN), Libramiento Norponiente 2000,

Fracc. Real de Juriquilla, Quéretaro, C.P. 76230 Qro., Mexico. (3) Universidad Michoacana de

San Nicolás de Hidalgo, Morelia Mich. Mexico. (4) Universidad de Sonora, Hermosillo, Son.,

México.Querétaro, Qro. 76010. [email protected]; *[email protected]

Important aspects of engineering involving processing of granular materials in operations

such as transportation, drying, screening, tempering, milling, packaging and quality

control. The performance of those operations requires experimental values of basic

mechanicals properties of the grain endosperm such as modulus of elasticity, failure

stress, and strain among others. The mechanical properties of wheat kernels were

determined using a uniaxial compression method from conventional texturometer and an

ultrasonic method. A high correlation coefficient (r = 0.727; P<0.0001) was found

between elastic modulus of wheat calculated using ultrasonic 54 kHz method and an

uniaxial compression method at 0.3 mm of strain and 0.1 mm s-1

of deformation velocity.

Data showed that elastic modulus increased with kernel hardness. In wheat kernels with

7.5 % moisture content the elastic modulus determined with ultrasonic method was 147-

160 MPa for soft wheat, 176 MPa for bread wheat and 201-210 MPa for durum wheat.

Using uniaxial compression method was 231-310 MPa for soft wheat, 391 MPa for bread

wheat and 403-465 MPa for durum wheat.

Although the elastic modulus of both methods are in agreement with most of the reported

data, the values obtained from the uniaxial compression method was about 2 times higher

than that obtained using ultrasonic method. This study showed that the compression load

method and the ultrasound may be a promising tool for rapid, nondestructive

measurement of wheat quality.

(keywords: wheat, compression load, uniaxial, elastic modulus, ultrasonic)


202

ET-18

Edible Film Based on Candelilla Wax to Improve the Shelf

Life and Quality of Hass Avocados

Saucedo-Pompa, S., Rojas-Molina, R., Aguilera-Carbó, A. F., Saenz-Galindo, A., De La Garza-Toledo, H.,

Jasso-Cantú, D., Aguilar, C.N. 1 Departamento de Investigación en Alimentos. Facultad de Ciencias Químicas. Universidad Autónoma de

Coahuila. Blvd. Venustiano Carranza 25280, Saltillo, Coahuila, México. Saltillo 25000 Coahuila, México.

*E-mail: [email protected] 1Universidad Autónoma Agraria “Antonio Narro” Calzada Antonio Narro 1923 Buenavista, Saltillo,

Coahuila, México.

An edible film (EF) is defined as a thin and continuous layer containing a bioactive

compound, which must be produced from materials which can be ingested and is used to

coat fruit. EF also can to modify some aspects of fruit maturation as it reduce the weight

loss due to its selective permeability to gases. An effective antifungal bioactive

compound is the ellagic acid (EA), a phenolic compound that also protects against

ultraviolet light, attack by insects and microorganisms. In this study the effect of addition

of EA into candelilla wax matrix on shelf life and quality of whole Hass avocados was

studied. The fruits were chosen for their maturity, size, free from infection and physical

defects. The treatments were: EF elaborated with candelilla wax and AE at three

concentrations, control without AE and untreated control. All those samples were

inoculated with a suspension of spores of Colletotrichum gloeosporioides. It was

completely divided into randomized groups. Changes in appearance, solids content, pH,

Aw, lightness (L* value) and weight loss were monitored during 6 weeks every 8 days. A

sensory evaluation of avocados with the best EF was also analyzed. The EF´s were able

to reduce significantly the damage caused by Colletotrichum gloeosporioides, reducing

also significantly the change in appearance and weight loss in the fruits. Use of EA as

part of the EF has an important effect to improve the quality and shel life of Hass

avocado. With this work we found that using this new technology can be successfully

protect against Colletotrichum gloeosporioides the main phytopathogenic fungus

affecting Hass avocado.

(keywords: candelilla wax, Colletotrichum gloeosporioides, avocado, ellagic acid)


203

ET-20

Optimization of Nanocapsules Formation of Safflower, Soybean and Sunflower Oils

by the Diffusion-Emulsion Method

Zambrano-Zaragoza M. L., Mercado-Silva E., Quintanar-Guerrero D.

Laboratorio de Posgrado en Farmacia, Facultad de Estudios Superiores Cuautitlán Universidad Nacional

Autónoma de México, C. Izcalli C.P. 54740.

2Departamento de Investigación y Posgrado en Alimentos, Facultad de Química. Universidad Autónoma de

Querétaro, CU, Cerro de las Campanas s/n. Col. Las Campanas. [email protected]

Edible oils are widely used as colorants, flavors solvents in food industry as well as oily

phase in emulsions, which make them important as food processing ingredients. The

development of nanoparticulated systems is a promising technological alternative that

seems to have important potential to food preservation. The aim of the present work was

to establish appropriate conditions to produce polymeric nanocapsules containing food

grade safflower, soybean, and sunflower oil in their core by the diffusion-emulsion

method, using food grade materials. A 23 factorial design with five central points was

used to optimize the process. Stirring rate (rpm), polyvinyl alcohol content (PVAL) (%

w/v) and poly--caprolactone content (mg), with safflower oil as oily core, were

considered as main factors. The analyzed response variables, in order of importance,

were particle size (nm), polydispersion index (PDI), density and - potential. It was

established that density is mainly influenced by polymer content ( = 9.54-1.018 g/cm3),

conforming the presence of capsular structures. For particle size (187-1380 nm) and PDI

(0.003-0.655) were mainly affected by PVAL content, stirring rate and the interaction

between the stabilizer and stirring rate. Scanning Electron Microscopy (SEM)

micrographs showed a vesicular structure formed by a polymeric membrane and an oily

core of submicronic size. The best conditions found were 4000 rpm, 5.0% PVAL and 200

mg of poly--caprolactone, predicting a response of 353 nm, =1.001 g/cm3 and PDI =

0.065. The versatility and reproducibility of the system was confirmed by using

sunflower and soybean oil. We conclude that nanocapsules formation is possible from

food grade materials with the desired size (311 and 341 nm), density, 0.999 g/cm3, and

PDI 0.08. This nanoparticulated system could have applications on food surfaces, and to

control water loss from fresh fruits.

(key words: nanocapsules, soybean oil, sunflower oil, safflower oil)


204

ET-21

Development and Characterization of Novel Edible Films Based on Mixtures of

Quinoa Protein and Chitosan

Lilian Abugoch; Cristian Tapia; María C. Villamán

Dpto. Ciencia de los Alimentos y Tecnología Química. Facultad de Ciencias Químicas y Farmacéuticas.

Universidad de Chile. Vicuña Mackenna 20, Santiago Chile

*[email protected]

The increasing interest in the development of edible films and coatings is due to their

great potential because they can be made from a variety of materials to control water and

oxygen transfer and improve food quality and shelf life. Naturally renewable biopolymers

have attracted much research interest in recent years to be used as edible biodegradable

films and coatings for food packaging. Quinoa, called the “mother of all grains”, is

classified by NASA as a Controlled Ecological Life Support System, and the National

Academy of Sciences of the United States declared quinoa as one of the 36 potential

cultivations in the world. Quinoa has protein content between 12 and 17% with high

quality amino acid balance. Chitosan is the N-deacetylated derivative of chitin, with a

degree of deacetylation of not less than 65%, chitin is the most abundant natural polymer

after cellulose, with which it has structural similarities. The aim of this work was to

formulate edible films based on mixtures of a water protein extract of quinoa (EAP) and

a solution of chitosan (Qo). Determine their mechanical properties, and to choose the best

ratio (EAP/Qo, v/v) for making this mixture film. The drying kinetic of both films

(mixture and Qo) was also studied. The sorption isotherm properties of the mixture film

were determined, analyzing them by the models of BET and GAB. The chosen extracting

protein process was the most efficient according to the yield versus the process time,

obtaining a 11.2 % in 1,5h. The selected mixture film has a ratio (EAP/Qo)(v/v) of (1:1).

In this ratio, the protein content contributed to the mechanical properties, presenting an

adecuate firmness and rigidity characteristics (2.01 ± 0.55 MPa), and an elasticity (273.4

± 21.6 %). This elasticity value was four times bigger than the Qo films. The protein

content effect showed the advantage of reducing the water vapor permeability (TVA) and

water activity (aw). The sorption values fitted well both models.

(keywords: quinoa proteins, chitosan, edible film)


205

ET-22

Vitamin Content of Tomato Fruit Stored Under Controlled

Atmosphere Conditions

Valverde-Juarez, F.; Lopez-Angulo, G.; Vega-Garcia, M.

Maestría en Ciencia y Tecnología de Alimentos, Facultad de Ciencias Químico-Biológicas, Universidad

Autónoma de Sinaloa, Av de las Américas y Josefa Ortíz S/N, Culiacán, Sin., 80010.

[email protected]*

Tomato fruit (Lycopersicon esculentum M) is one of the most commercialized

horticultural crops in the world. It is important in human nutrition because is widely

cultivated and consumed in different forms, representing an important source of vitamins

A and C, β-carotene, potassium and lycopene. However, tomato is a highly perishable

fruit and it is sensitive to low temperatures, therefore, its storage and commerce is limited

in the case of distant countries which represents an opportunity of commerce for Mexican

producers. An alternative to solve this storage problem could be the use of controlled

atmospheres (CA). This technology has been studied in a wide variety of horticultural

products finding considerable variations in response to storage conditions. The aim of

this study was to investigate the effect of CA storage on the nutritional quality and

postharvest life of tomato fruit. Mature green tomato cv Imperial were stored at 12 °C

under refrigeration or controlled atmosphere (3-4% O2 and 0% CO2) at 12 ºC for 21 days

and then transferred at 23 °C on air for 12 days. Three fruits per treatment were taken

after 0, 4, 8, and 12 days of the second storage to determine the firmness, skin color,

respiration and the content of vitamins A (β-carotene) and C by liquid chromatography

(HPLC). Fruits stored under CA maintained firmness and vitamin C content better than

those stored under refrigeration. β-carotene content was not affected by CA storage while

respiration was increased. CA storage was more effective in delaying the loss of green

color than refrigeration.

(keywords: controlled atmosphere, tomato, vitamins, respiration)


206

ET-23

Mechanical and Thermal Properties of Films Made from Oxidized Banana Starch

and Glycerol

García-Tejeda Y., Romero-Bastida, C. A., González-Soto, R. A., Sánchez-Rivera M.M.,Bello Pérez, L. A.,

Solorza-Feria, J.

Centro de Desarrollo de Productos Bióticos. Instituto Politécnico Nacional. Carr. Yautepec-Jojutla km 8.5.

Col. San Isidro, C.P.62731 Yautepec Morelos. [email protected]; [email protected]

Pollution caused by plastic containers derived from petroleum has increased substantially

during the last years, degradable materials are then required to substitute them. Starch is a

biodegradable molecule, cheap and easily available in nature, that when modified,

improves its physical and functional properties, conferring them to the products where it

is used. The objective of this work was to study the mechanical and thermal properties of

films made from oxidized banana starch and glycerol. Starch isolated from macho banana

(Musa paradisiaca L ), was oxidized with sodium hypochlorite (3%w/v active chlorine),

mixtures containing 65%(w/v in all cases) of native (control) or oxidized starch, 18%

water and 17% glycerol, were processed in a Beultespacher Extruder to elaborate the

films. The mechanical properties: tensile strength, tensile modulus and strain at break

were measured at 0, 15, 30 and 45 storage days using a TA-XT2i Texturometer. The

transition temperature and enthalpy were measured using a TA Instruments Differential

Scanning Calorimeter, sweeping the temperature range from 20 to 270º C at 10º C/min.

One way analysis of variance was applied to the data. The results showed that there were

no significant differences in the tensile strength between both native and oxidized starch

films at the beginning of the storage. As the time passed, an increase in tensile strength

was seen in native films up to 30 and 15 storage days for native and oxidized starch films

respectively. The tensile modulus values did not show difference between the two films

all along the storage. A significant decrease was observed in the strain at break in native

starch films at the end of the storage, while no significant differences were exhibited by

oxidized starch films. The transition (melting) temperature of native starch films

decreased significantly in 45 storage days, while in oxidized ones, a non-significant

decrease was seen in the same period of time. A significant increase in the enthalpy

values was observed for both native and oxidized starch films, indicating a higher energy

requirement to break the films structure as the storage progressed. Changes in starch

crystallinity may have influenced the described tendencies.

(keywords: tensile tests, thermal properties, banana starch films)


207

ET-24

Characterization of Polysaccharide-based Films with potential use as Enteric

Coating: A Comparative Study

Espinoza-Herrera, N. San Martín-Martínez, E. Pedroza-Islas, R.. Cruz-Orea,A. Tomás,S.

Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN.

Legaria 694, Col. Irrigación, 11500 D.F. México. (1)* [email protected], (2) [email protected], (3)

[email protected]

Delivery of sensitive bioactive ingredients to the colon is a common practice in the

pharmaceutical industry, and has a growing attention in the food ingredients industries.

This challenge in drugs is usually overcome by the use of enteric coating. Is still a

challenge for the food industry to find a reliable formulation of food grade enteric

coating, which has environment stability in both stomach and intestine, and it is able to

release the active ingredient in the colon. For colony delivery, several natural polymers

such as those found in the diet, are preferred over synthetic materials because they are

safer and more available. The aim of this work was to evaluate some physical properties

of different biopolymers with potential use as enteric coatings. Biopolymers used were:

pectin (P), carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl

cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), and waxy corn starch (A).

Aqueous solutions (3%w/v) were prepared and 20 ml of each solution was spread onto 11

cm diameter polyethylene casting plates, and then dried a room temperature for 24 h or

until they were completely dried. The open photo-acoustic cell (OPC) technique was used

to obtain the thermal diffusivity (), obtaining for P the highest value of 16.321 x10-4

cm2

s-1

and the lowest value were for the HPC and MC with a value of 6.732 and 5.932 x10-4

cm2 s

-1 respectively. The percentage of crystallinity obtained by X-ray diffraction patterns

showed that P has a value of 17.10% and 4.19% and 2.93% for MC for HPC having a

relationship between the crystallinity and thermal diffusivity. Mechanical properties of

the films, indicated that tensile strength ranged from 69.16-9.26 MPa for the CMC and P

respectively, the percentage elongation was 12.55% for HPC and 2.64% for A, the

Young's modulus ranged from 1912.20 - 374.98 MPa for CMC and P respectively. The

results indicated that Pectin polymers may have the highest thermal diffusivity because it

is more crystalline than the other polymers, and from the mechanical properties it is more

fragile.

(keywords: polisaccharide, thermal diffusivity, X-ray diffraction, mechanical properties)


208

ET-25

Infrared Heating (micronizing) Effect on the Cooking time of five Mexican

Cultivars of Common Beans (Phaseolus vulgaris L.)

Gallegos-Infante, J.A., Rocha-Guzman, N.E., Gonzalez-Laredo, R.F., Delgado-Licon, E., Arntfield S.

Cenkowski, S.; Hernandez-Lira, J.C.

1 Departamento de Ingenierias Química y Bioquímica, Instituto Tecnológico de Durango. Blvd. Felipe

Pescador 1830 Ote, Durango, Dgo., México CP 38080. [email protected] 2 Department of Food Science and Technology, Manitoba University, Winnipeg, Canada.

Common beans are a traditional basic food in the diet of Latin-American people.

Unfortunately cooking time in several cultivars could be quite long, and this may be

reason of their declining use. The objective of this work was to evaluate the aplication of

micronizing technology on the cooking time of five Mexican cultivars of common beans

(Pinto villa, Negro San Luis, Flor de Mayo, Canario y Bayo Victoria). Laboratory

micronizer equipment developed in Manitoba University with infrared lamp was used,

with constant λ and distance separation between heat source and sample (0.10 m).

Evaluation of cooking time was carried out according to the Method of Mattson, with

slight modifications of that of the Canadian International Grain Institute (CIGI). Water

absorption capacity, water absorption index and emulsifying capacity were determinated

following the Anderson method. Results showed that cooking time was influenced by

cultivar, micronizing time and humidity. The lowest effect of micronizing was for Bayo

cultivar, where the reduction of cooking time was only of 30 % at low humidity

conditions and 45 % at higher humidity conditions. The cultivar with more effect on the

cooking time was Negro San Luis, probably due to better absorption of radiation

associated to its black color. At low humidity condition, the reduction of cooking time

was of 50% in comparison with samples without micronizing; but at higher humidity the

reduction increase to 80 % of reduction of cooking time. Water absorption capacity was

affected by the micronizing, and higher water absorption was associated to the Negro San

Luis cultivar. Therefore, it seems that there is a link between increase of water absorption

and lower cooking time. Water absorption index was not influenced by micronizing, but

the emulsifying capacity increased. We conclude that the use of infrared heating, can

change the cooking time of Mexican cultivars of common beans. The use of this

technology could be help to reduce processing time in common beans.

(keywords: common beans, cooking time, micronizing, water absorption capacity)


209

ET-26

Effects of Edible Cactus-Mucilage Coating on Quality and Shelf Life of

Strawberries (Fragaria ananassa)

May-Gutiérrez, M. E., Martínez-Soto, G., Bautista-Justo, M., Castaño-Tostado, E.

Departamento de Ingeniería de Alimentos, Instituto de Ciencias Agrícolas de la Universidad de

Guanajuato, carr. Irapuato-León km 9.0 ExHacienda El Copal, Irapuato, Guanajuato, México 36570

[email protected]; [email protected]

Fresh strawberry (Fragaria ananassa) is a very perishable fruit with a short shelf life.

There is an interest of both marketers and consumers to extend fresh strawberry shelf life.

Strawberries are also susceptible to water loss, bruising and mechanical injuries due to

their soft texture and lack of a protective rind. Edible coatings have long been known to

protect perishable food products from deterioration by retarding dehydration, suppressing

respiration, improving textural quality, helping retain volatile flavor compounds and

reducing microbial growth. Cactus mucilage may find applications in food, cosmetics,

pharmaceutical and other industries. An important point in the choice of the cactus

mucilage as a coating is its low cost. The aim of this work was to develop an edible

coating which preserves the quality of strawberry. Strawberries were treated either with

2% glycerol or sorbitol, as plasticizing agents. Strawberries were dipped in coating

solution for 40 s, the excess coating was drained and the coated strawberries were dried

in a forced-air dryer (20 ºC) for 30 min. Strawberries dipped in distilled water were used

as a blank. The influence of cactus stems–mucilage coating formulations on quality

attributes of strawberries stored at 5 and 10 ºC and a relative humidity of 80 % was

studied. The effectiveness of the treatments was assessed by evaluating their impact on

the following parameters: weight loss, external color, firmness, soluble solids content,

pH, titratable acidity, and sensory evaluation. The total count was determined using the

pour plate method. Cactus-mucilage coating significantly reduced decay of strawberries

(P ≤ 0.05). There was significant difference between glycerol and sorbitol treatments up

to 15 days of storage. Coated strawberries produced the lowest ratios of chromaticity

parameters compared with the control fruits (1.81-1.56). All coatings showed a beneficial

effect on firmness retention (19–25 N). Cactus mucilage coatings had a marked effect on

tritratable acidity of strawberries stored (1.39-1.45). Coatings were considered to retain

overall sensory quality when compared with uncoated strawberries. The results revealed

that applying an edible cactus-mucilage coating effectively enhanced the quality

attributes and extend the shelf life of strawberry fruit.

(keywords: strawberries, edible coating, cactus stem–mucilage, quality, shelf life)


210

ET-27

Mechanical Properties Comparison for Thin Films made of Whey Protein Isolate

added with Glucose Oxidase and/or Nisin as Antimicrobial Agents

Ramírez-Jiménez C., Murillo-Martínez M., Guerrero-Legarreta I. and Ponce-Alquicira E.

Área de Bioquímica de Macromoléculas, Departamento de Biotecnología, CBS, Universidad Autónoma

Metropolitana Iztapalapa. Apartado postal 55-535, México City, México. [email protected]

Whey protein isolate (WPI) is a biomaterial of interest in the production of edible

packaging since it provides excellent mechanical and barrier properties. Incorporation of

antimicrobial agents into WPI matrix could enhance the control of microorganisms

present in foods. The present work analyzes the mechanical properties described by

Young´s modulus E, strength σ and elongation ε of thin films made of WPI added with

different concentrations of nisin (N), glucose oxidase (GO) and a combination of both (N:

0, 0.3 and 1.2; GO: 0, 2.4 x 10-3 and 0.05 % w/v). The influence of pH (5.5 and 8.5) on

the films mechanical response was also analyzed. Considering the material being

isotropic and according to ASTM D 882-2, specimens from each material were cut out

and tested at the TA-XT2i Texture Analyzer using mechanical grips. The entire set of

materials was divided into two groups depending on their pH value. Group 1 films with a

pH value of 5.5 showed higher antimicrobial activity than Group 2 with pH of 8.5.

Nevertheless, the mechanical response for Group 1 compared against Group 2 showed a

clear reduction for E, σ and ε, values. Obtained data were 2.64±0.16MPa, 6.29±0.29MPa

and 6.27±1.39% for GO-films made at pH 5.5; while figures obtained for GO-films at pH

8.5 were 3.34±0.17 MPa, 9.79±0.53 MPa and 17.86±5.25% for E, σ and ε, respectively.

It was also observed that films added with GO at its two concentrations showed very

similar values for E, σ and ε at both tested pH values. Addition of N did have a

significant effect on the mechanical properties depending upon its concentration; high N

levels resulted on a high value for E (3.84±0.19 MPa) whereas films with low level of N

presented the lowest value of E (1.73±0.04 MPa) for pH 8.5 films. For both pH values,

films added with a combination of GO and Ni showed a similar response of E (2.16±0.04

MPa) yet, σ (6.70±0.18 MPa) and ε (18.68±8.36%). Therefore, inclusion of GO improve

both mechanical and antimicrobial performance of WPI films under the tested conditions.

(keywords: WPI, films, mechanical properties, glucose oxidase, nisin)


211

ET-28

High Voltage Pulsed Electric Fields as an Alternative for Production

of High Quality Fruit Juices

Ortega-Rivas, E.

Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Campus Universitario I. Chihuahua,

31170 Chih. México. Tel. (614) 4134795, Fax (614) 4144492, e-mail: [email protected].

High voltage pulsed electric field (PEF) treatment is a promising non-thermal processing

method that may radically change liquid food preservation technology. Treating liquid

foods with high voltage pulsed electric fields may inactivate micro-organisms and

enzymes with only a small increase in temperature, simultaneously providing consumers

with safe, nutritious, and fresh-like quality foods. PEF can be used to produce fruit juices

of high quality and safe for consumption at the same time. This paper presents results in

application of PEF to different fruit juices.

(keywords: non-thermal processing, pulsed electric fields, fruit juice pasteurization,

sensory attributes)

01 emerging technologies and food packaging

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