• Food Science of Animal Resources
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• v.32 no.5
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• pp.627-634
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• 2012

This study was carried out to investigate the physical and thermal properties of ${\kappa}$-carrageenan (${\kappa}$-car) gel added whey protein isolate (WPI) as a cryoprotectant. The concentration of ${\kappa}$-carrageenan was fixed at 0.2 wt%. The mean ice crystal size of the WPI/${\kappa}$-car was decreased according to increasing whey protein isolate concentration. The temperature of gel-sol (Tg-s) and sol-gel (Ts-g) transition of WPI/${\kappa}$-car maxtrix was represented in the order of 3.0, 0.2, 5.0 and 1.0 wt%. In addition, the transition temperature of gel-sol of WPI in sucrose solution were showed in order of 1.0, 5.0, 0.2 and 3.0 wt% depending on whey protein isolate concentration. The shape of ice crystal was divided largely into two types, round and rectangular form. 1.0 wt% WPI/${\kappa}$-car matrix at pH 7 and 9 showed minute and rectangular formation of ice crystals and whey protein isolate in sucrose solution at a concentration of 1.0 wt% WPI/${\kappa}$-car matrix at pH 3 and 5 showed relatively large size and round ice crystals. The ice recrystallization characteristics and cryprotective effect of ${\kappa}$-carrageenan changed through the addition of different concentrations of whey protein isolate. It seems that the conformational changes induced interactions between whey protein isolate and ${\kappa}$-carrageenan affected ice recrystallization.

• Journal of the Korean Society of Food Culture
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• v.24 no.5
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• pp.561-569
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• 2009

The effects of substituting whey protein isolate (WPI) powder for rice flour during the preparation of paeksulgi (Korean rice cake) were evaluated by objective and subjective tests. Milk whey is drained from milk curd as a by-product of the cheese manufacturing process. Whey protein is known as a good nutritional source and a functional material for many processed foods. WPI contains more than 90% whey protein. The moisture content decreased gradually during storage and the decrease was less in control than WPI powder-substituted groups. The color lightness (L) decreased significantly with increasing WPI powder, wherease the redness (a) and yellowness (b) both increased. Texture analyses revealed that the hardness, chewiness, gumminess, adhesiveness and fracturability of paeksulgitended to increase in proportion to the amount of WPI powder added. Evaluation of the gelatinization of paeksulgi by amylographing revealed that the initial pasting temperature, peak viscosity, hot pasting viscosity and breakdown was lower in samples that contained WPI powder. However, the lowest setback value was observed in the control. The results of the sensory evaluation indicated that paeksulgi prepared with 2% WPI powder had the highest overall acceptability. Taken together, these results suggest that WPI paeksulgi containing 2% WPI powder has the best quality.

• Korean journal of food and cookery science
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• v.23 no.1 s.97
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• pp.41-49
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• 2007

The substitution effects of whey protein isolate(WPI) for egg in the preparation of sponge cake were determined by objective and subjective tests. Milk whey is drained from milk curd as a by-product of cheese manufacture. Whey protein is known as a good nutritional source and a functional material for many processed foods, especially baked goods. WPI contains above 90% whey protein. The specific gravity and viscosity of sponge cakes tend to be affected by WPI substitution. The cooking loss of sponge cakes with WPI substituted for egg(abbreviated as WPI cake) during oven baking was smaller than that made with egg(abbreviated as egg cake) and the specific loaf volume of WPI cake was larger than that of egg cake. The number of pores was highly increased and the size of pores was more uniformly and finely distributed in the cross section of WPI cake than those of egg cake, as observed by scanning electron microscopy(SEM). The hardness, gumminess and chewiness of WPI cake made with 10-20% WPI substitution were the lowest among all the tested cakes, including egg cake, thereby confirming the considerable improvement in their cake qualities. By the results of sensory evaluation, appearance, pore uniformity, softness, chewiness, moistness, flavor, mouth feeling, and overall acceptability of 10-20% WPI substitute cakes were evaluated as being significantly superior to those of all other cakes(p<0.05). These results support the better physicochemical characteristics and sensory evaluations of sponge cake prepared with 10-20% of WPI substitution for egg.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1315-1320
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• 2011

Whey protein (WP) is a mixture of proteins, and is of high nutritional values. WP has become an important source of functional ingredients in various health-promoting foods. In this study, size-exclusion chromatography (SEC) and asymmetrical flow field-flow fractionation (AsFlFFF) were used for separation and analysis of whey proteins. It was found that a lab-prepared WP from raw milk is mostly of ${\beta}$-lactoglobulin with small amount of higher molecular weight components, while a commercial whey protein isolate (WPI) powder contains relatively larger amount of components other than ${\beta}$-lactoglobulin, including IgG and protein aggregates. Results suggest that AsFlFFF provides higher resolution for the major whey proteins than SEC in their normal operation conditions. AsFlFFF could differentiate the BSA and Albumin, despite a small difference in their molecular weights, and also was able to separate much smaller amount of aggregates from monomers. It is noted that SEC was able to show the presence of low molecular weight components other than the major whey proteins in the WP samples, which AsFlFFF could not show, probably due to the partial loss of those low molecular weight species through the membrane.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1488-1494
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• 1999

Effect of ${\gamma}-irradiation$ on the SDS-PAGE pattern, secondary structure content, the solubility of commercial soy protein isolate (SPI) and whey protein concentrate (WPC) was investigated. The change in the subunit molecular weight of SPI and WPC irradiated in aqueous solution or dried state was studied using SDS-PAGE. The SDS-PAGE pattern of SPI irradiated in aqueous solution revealed the fragmentation and aggregation of the subunit protein. For WPC irradiated in aqueous solution. fragmentation of the subunit protein up to 10 kGy was observed. In contrast, ${\gamma}-irradiation$ of SPI and WPC in dried state did not cause any significant changes in the SDS-PAGE pattern. The change In the secondary structure of irradiated SPI and WPC solution was studied using circular dichroism. The aperiodic structure content of SPI and WPC solution increased at higher irradiation doses, which suggests that ${\gamma}-irradiation$ caused the disruption of the ordered structure of SPI and WPC solution. Gamma-irradiation also caused the change in solubility of SPI and WPC in dried state.

• Preventive Nutrition and Food Science
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• v.13 no.4
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• pp.370-374
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• 2008

The Gelidium corneum (GC)-whey protein isolate (WPI) blend film containing grapefruit seed extract (GSE) was prepared by incorporating different amounts (0, 0.02, 0.04, 0.08, 0.1%) of GSE into the film. The film's tensile strength (TS) and water vapor permeability (WVP) were improved by the addition of GSE. The film containing 0.1% GSE had a TS of 3.27 MPa, whereas the control had 2.64 MPa. WVP of the film was also significantly decreased by the addition of GSE. Addition of 0.1% GSE decreased the populations of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium by 1.0, 1.6, and 0.6 log CFU/g, respectively, compared to the control. Fish paste was packed with the GC-WPI blend film containing GSE, and microbial change in the fish paste inoculated with E. coli O157:H7, L. monocytogenes, and S. Typhimurium during storage was examined. Populations of E. coli O157:H7, L. monocytogenes, and S. Typhimurium were decreased by 0.60, 0.48, and 0.85 log CFU/g, after 7 day of storage, respectively. These results suggest packaging fish paste in the GC-WPI blend film containing GSE can extend the shelf life.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.324-329
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• 2008

The effect of ultra-high pressure homogenization on the emulsifying properties of whey protein was investigated in a model emulsion made with whey protein isolate and soya oil under various pH. The emulsifying properties, the average diameter of the oil droplets ($d_{vs}$), and the protein load, were measured for each emulsion produced at different homogenization pressures (50 to 200 MPa) and pH values (4.6 to 8.0). According to the results of variance analysis and response surface, the pH had more influence on oil droplet size and protein load than homogenization pressure. The model equations, which were obtained by response surface analysis, show that pH and homogenization pressure had the major effect on oil droplet size and protein load. Higher homogenization pressure decreased the average droplet size and the protein load. Homogenization at high pressure, as opposed to low pressure, causes no overprocessing, but the effect was pH-dependent. The average diameter of the oil droplets increased slightly by decreasing the pH from 8.0 to 6.5 and then increased dramatically toward the isoelectric point of whey protein (i.e., at pH 4.6). Moreover associated droplets were found at acidic pH and their size was increased at high temperature.

• Food Science of Animal Resources
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• v.31 no.4
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• pp.543-550
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• 2011

Various concentrations of whey protein isolate (WPI), such as 0.1, 0.5, 1.0, 2.5, and 5.0%(w/v), containing 1.0%(w/v) eugenol were prepared by high speed homogenization to formulate nanoemulsions (NEs) and to investigate their antimicrobial activity. The results showed that particle size decreased according to increases in WPI concentration. Similarly, the ${\zeta}$-potential value was reduced to a negative charge when using WPI concentrations >0.1%(w/v). In contrast, no significant differences in particle size were observed during 1 mon of storage, except for the 0.1%(w/v) WPI NE. The ${\zeta}$-potential value depended on the increase in WPI concentration and storage duration, except for NE1 and NE5, suggesting that a low or high concentration of emulsifier was not effective for maintaining the droplet form of the eugenol NE. The results of an antibacterial effect investigation indicated that the growth of Escherichia coli was inhibited based on an increase in eugenol concentration in all NE formulations. Moreover, a membrane permeability study showed that total leakage content increased according to incubation time.

• Journal of the Korean Society of Food Culture
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• v.22 no.1
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• pp.97-103
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• 2007

In this study, physicochemical properties and the antioxidative activity of whey protein isolate(WPI) for com germ oil were measured. The pH of WPI was 6.26, and the titrable acidity was 0.18%. The WPI’s moisture content was 5.2% and each of the other element content such as lactose, crude protein, crude ash and crude fat was found to be 0.8%, 90.7%, 2.7% and 0.6%, respectively. The amounts of active SH group in WPI 9 ${\mu}$ M-g and total colony counts of bacteria was 5.9 ${\times}$ 10$^3$ CFU-g. ${\alpha}$-Lactalbumin, ${\beta}$-lactoglobulin and bovine serum albumin(BSA) were shown in WPI as major protein by electrophoresis. The antioxidative effect of WPI and other antioxidants on com germ oil used as substrate was determined by peroxide value(POV) and conjuqated dienoic acid value(CDV). By these results, the order of antioxidative effects could be defined as BHT 0.02%>ascorbic acid 0.1%>WPI 0.1%>WPI 0.02%>ascorbic acid 0.02%>control>tocopherol 0.02%>tocopherol 0.1%, respectively. Also the induction period of com germ oil added with WPI was longer by 1.6 times than that of control(none added any antioxidant). Therefore the fact suggested that WPI could be utilized as a good antioxidative agents.

• Korean Journal of Food Science and Technology
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• v.39 no.1
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• pp.50-54
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• 2007

In this study, the physicochemical properties of cheese whey protein isolate (WPI) were measured. The total amount of amino acids in WPI was 89.5% and the proportion of essential amino acids was 44.6%. Among these, leucine, lysine, isoleucine, and valine were shown in large amounts. At various pHs, the solubility of WPI (82-88%) was higher than that of sodium caseinate, (5-79%). The solubility of WPI was not affected by variation of pH. It was shown that the emulsifying capacity of WPI was higher than that of egg yolk by 1.6 times, but the stabilities of emulsions made with WPI and egg yolk was almost same each other at 65-97% and 60-89%, respectively. The foaming capacity of WPI was higher than that of egg white, at 323.3% and 186.6%, respectively, but the foam stability of WPI was similar to that of egg white.