• 한국축산식품학회지
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• 제32권5호
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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.

• 한국식생활문화학회지
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• 제24권5호
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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.

• 한국식품조리과학회지
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• 제23권1호통권97호
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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.

• 한국식생활문화학회지
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• 제22권1호
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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.

• 한국식품과학회지
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• 제39권1호
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• pp.50-54
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• 2007

단백질을 식품의 원료로서 여러 가지 식품에 응용하려고 할때 제일 먼저 문제되는 것이 영양가이지만 동시에 물리화학적 특성도 식품 원료로서의 적합성을 결정하는데 중요한 요인이 되고 있다. 그런 면에서 유청(cheese whey)의 성분에서 단백질 함량을 90% 이상으로 농축 분리시킨 whey protein isolate(WPI)는 단백질 보충제로서 뿐만 아니라 다양한 물리화학적 특성을 가지고 있기 때문에 여러 가지의 가공식품에 이용할 수 있다고 사료된다. 따라서 본 실험에서는 WPI의 아미노산 함량, 용해성, 유화성, 기포성을 조사하여 식품의 기능성 원료 및 대체물로서의 이용 가능성을 알아보고자 하였다. WPI의 총 아미노산 함량은 89.5%였고 그 중에서 필수 아미노산 함량이 44.6%를 차지하였다. 필수 아미노산 중에서는 leucine, isoleucine, valine 등의 BCAA(branched chain amino acid) 함량이 높았다. pH에 따른 WPI의 용해성은 82-88%의 범위로 pH의 영향을 받지 않았고 유화용량은 302.7mL/g으로 난황의 187.0mL/g보다 높았으며 시간이 경과함에 따라 유화액의 이장량으로 측정한 유화안정성도 65-97%로 나타나 난황의 60-89%보다 안정함을 보였다. 기포형성력은 323.3%로 난백의 186.6%보다 약 2배 정도 높았고 시간이 경과함에 따라 남은 기포의 부피로 측정한 기포안정성은 85.9-97.7%로 난백의 84.8-95.3%와 유사하였다. 이상의 결과에서 WPI는 우수한 단백질 보충제로서 뿐만 아니라 용해성, 기포성, 유화성도 우수하게 나타났으므로 각종 가공식품의 품질향상에 영향을 주는 기능성 원료 및 대체물로서의 활용도가 매우 높을 것으로 사료된다.

• 한국식품과학회지
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• 제42권2호
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• pp.165-174
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• 2010

본 연구에서는 버터 스폰지 케이크 제조시 버터 대신 WPI를 여러 가지 비율로 대체하여 제조한 후 반죽의 특징 및 제품의 품질 특성을 평가하였다. WPI 대체율이 증가할수록 케이크 반죽의 비중은 일정하게 감소하였지만 점도는 일정한 경향을 보이지 않았고, 완성된 케이크의 굽기손실율은 감소하면서 비용적은 증가함을 보였다. 외형은 W-20과 W-40이 가장 바람직한 버터 스폰지 케이크의 형태를 가지는 동시에 질감도 control과 유사한 정도로 부드러웠다. WPI 80% 이상 대체의 경우 케이크의 부피는 커졌지만 WPI의 열에 의한 응고로 인해 부드럽다기보다는 오히려 무겁고 단단한 케이크가 되었다. WPI 대체량이 증가할수록 케이크의 수분함량이 감소하면서 응집성, 탄성, 복원성이 감소된 반면 경도, 씹힘성, 점착성, 부착성, 부숴짐성은 증가함을 보였고 케이크 중 W-20은 control과 비교시 모든 값에서 유의적으로 유사함을 보였다. 케이크의 crust 색은 WPI가 많을수록 명도와 황색도가 감소한 반면 적색도는 증가하였고 crumb의 경우 명도 결과만 상반된 변화를 보였다. 관능 결과에서도 W-20이 control과 비교해 볼때 가장 유사한 것으로 평가되었다. 이상의 결과에서 WPI 대체 버터 스폰지 케이크의 최종 품질은 이화학적 및 관능적 특성에서 가장 좋은 결과를 나타낸 W-20이 우수하였고 40% 이상 대체시에는 전체적으로 좋지 않은 결과를 보였다. 따라서 버터 스폰지 케이크 내에서 버터 대체물로 이용하는 WPI의 가장 적절한 대체비율은 20%로 제시할 수 있을 것으로 보인다. 그리고 케이크 이외에 유지를 사용하는 식품에도 적용될 수 있도록 WPI를 이용한 지방 대체 식품의 범위를 확대하는 방법에 대한 연구도 필요하다고 사료된다.

• 한국축산식품학회지
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• 제36권2호
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• pp.267-274
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• 2016

The purposes of this study were to investigate the impacts of concentration levels of whey protein isolate (WPI) and inulin on the formation and physicochemical properties of WPI/inulin nano complexes and to evaluate their potential prebiotic effects. WPI/inulin nano complexes were produced using the internal gelation method. Transmission electron microscopy (TEM) and particle size analyzer were used to assess the morphological and physicochemical characterizations of nano complexes, respectively. The encapsulation efficiency of resveratrol in nano complexes was studied using HPLC while the potential prebiotic effects were investigated by measuring the viability of probiotics. In TEM micrographs, the globular forms of nano complexes in the range of 10 and 100 nm were successfully manufactured. An increase in WPI concentration level from 1 to 3% (w/v) resulted in a significant (p<0.05) decrease in the size of nano complexs while inulin concentration level did not affect the size of nano complexes. The polydispersity index of nano complexes was below 0.3 in all cases while the zeta-potential values in the range of -2 and -12 mV were observed. The encapsulation efficiency of resveratrol was significantly (p<0.05) increased as WPI and inulin concentration levels were increased from 1 to 3% (w/v). During incubation at 37℃ for 24 h, WPI/inulin nano complexes exhibited similar viability of probiotics with free inulin and had significantly (p<0.05) higher viability than negative control. In conclusions, WPI and inulin concentration levels were key factors affecting the physicochemical properties of WPI/inulin nano complexes and had potential prebiotic effect.

• 한국축산식품학회지
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• 제31권4호
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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.

• 한국축산식품학회지
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• 제42권6호
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• pp.915-927
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• 2022

Recently, protein-fortified milk powders are being widely consumed in Korea to prevent sarcopenia, and the demand for high-protein food powders is continuously increasing in the Korean market. However, spray-dried milk proteins have poor flowability and wettability owing to their fine particle sizes and high inter-particle cohesive forces. Fluidized bed agglomeration is widely used to improve the instant properties of food powders. This study investigated the effect of fluidized bed agglomeration on whey protein isolate (WPI)-fortified skim milk powder (SMP) at different SMP/WPI ratios. The fluidized bed process increased the particle size distribution, and agglomerated particles with grape-like structures were observed in the SEM images. As the size increased, the Carr index (CI) and Hausner ratio (HR) values of the agglomerated WPI-fortified SMP particles exhibited excellent flowability (CI: <15) and low cohesiveness (HR: <1.2). In addition, agglomerated WPI-fortified SMP particles exhibited the faster wetting time than the instant criterion (<20 s). As a result, the rheological and physical properties of the WPI-fortified SMP particles were effectively improved by fluidized bed agglomeration. However, the fluidized bed agglomeration process led to a slight change in the color properties. The CIE L^* decreased, and the CIE b^* increased because of the Maillard reaction. The apparent viscosity (η_a,10) and consistency index (K) values of the rehydrated solutions (60 g/180 mL water) increased with the increasing WPI ratio. These results may be useful for formulating protein-fortified milk powder with better instant properties.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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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.