• Food Science and Industry
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• v.51 no.4
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• pp.302-312
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• 2018

Bioactive peptides generated from milk proteins play an important role in the prevention and alleviation of diabetes. Whey proteins possess direct insulinotropic effect by amino acids (especially branch chain amino acids) produced through its gastrointestinal digestion. Additionally, blood glucose level can be lowered by gut hormone which called incretin [glucose dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)]. However, physiological effects of incretin readily disappeared by dipeptidyl peptidase-4 (DPP-4) causing degradation of GLP-1. Several DPP-4 inhibitors are currently used as therapeutic medicines for the treatment of type II diabetes. More than 60 natural peptide (2-14 amino acids) DPP-4 inhibitors were identified in milk proteins. Peptide DPP-4 inhibitors act as substrate inhibitor and delay breakdown of GLP-1 both in vitro and in vivo. This review summarizes nutritional quality of milk proteins, absorption and mode of action of bioactive peptides, and finally up-to-dated knowledge on DPP-4 inhibitory peptides derived from milk proteins.

• Journal of Life Science
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• v.33 no.5
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• pp.383-390
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• 2023

The goal of this study was to identify new bioactive peptides in extracts derived from Tenebrio molitor (T. molitor) larvae for the development of functional foods. After extraction from freeze-dried T. molitor larvae with various solvents on time course, the extracts showed the highest 2,2,1-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity at 5 and 10 hr per total protein and solid contents, respectively. When the water extract was fractionated, a high methanol concentration led to a reduced level of high-molecular-weight proteins in the centrifugal supernatant, whereas increased DPPH activity in the supernatants suggests low-molecular-weight peptides may mediate antioxidant activity in the supernatant. Most of the organic solvent partitions, excluding butanol, showed similar activities in the water phases, and the organic solvent partition fraction exhibited a 28~44% decrease in activity following heat treatment, implying that some components in the fraction become unstable in the presence of heat. The addition of proteinase K to the water extract increased DPPH activity by 10~20%, suggesting that peptides, when released from total proteins, partially increase antioxidant activity. Therefore, we suggest that the antioxidants in T. molitor larval extracts make them a potential source of functional animal food.

• Food Science of Animal Resources
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• v.29 no.2
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• pp.238-244
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• 2009

Food allergy is a serious nutritional problem in both children and adults. Therefore, food allergenicity reduction methods are greatly needed. The allergenicity is altered by various manufacturing processes, and the digestibility of food proteins can be affected by food processing. This study was conducted to investigate the effect of in-vitro digestibility on the allergenicity of autoclaved market pork sausages using pepsin (30min) and trypsin (5, 30, 60, 90, and 120min). The binding ability of the porcine serum albumin (PSA) from sausages A and B significantly decreased by about 30 and 23%, respectively, after autoclave treatment (121; 5, 10, and 30 min). After the pepsin and trypsin treatments, the binding ability of products A and B at 30 min decreased. These competitive indirect enzyme-linked immunosorbent assay (ci-ELISA) results corresponded well with the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting results. The results demonstrated that the allergenicity of pork sausages considerably decreased after autoclave treatment, and were also maintained or decreased after enzyme treatment. Accordingly, autoclave treatment represents a promising processing technology for the reduction of the allergenicity of diverse food products.

• KSBB Journal
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• v.24 no.5
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• pp.458-462
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• 2009

Silk fibroin is a structural protein from Bombyx mori and can be sulfated to provide biofunctional polypeptides showing antiviral and anticoagulating activities. However, the sulfated fibroins have not been characterized enough to present their compositions and structures. In this report, sulfation reaction was investigated by varying the reaction temperature and sulfuric acid concentration and analysis of the resulting peptides were carried out. The degree of sulfation was proportion to sulfuric acid concentration but the maximum product yield was obtained at $60^{\circ}C$ and 5% of sulfuric acid concentration. FT-IR spectrum, UV absorption and NMR spectrum support that o-sulfate ester was formed at the hydroxyl group of serine and tyrosine residues. Size exclusion chromatography identified that sulfated fibroin was composed of a highly hydrolyzed polypeptide mixtures and peptides of relatively higher molecular weight.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.304-308
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• 2006

This study was performed to understand the behavior of protein mobility and intensity of enzymatic hydrolysis according to crosslinking of sodium caseinate, whey protein isolate, skim milk and whole milk powders with or without transglutaminase (TGase, w/w = 200 : 1) at $38^{\circ}C$. Whey protein was limited to crosslinking and skim milk was relatively more increased in high molecular polymer than whole milk. The degree of crosslinking decreased in the order of sodium caseinate>skim milk>whole milk>whey protein isolate. The SDS-PAGE results indicated that main bands of TGase treated samples had a high mobility and formed bands of molecular weights below 15 kDa by hydrolysis with pepsin after 10 min of reaction time. However, ${\beta}-lactoglobulin$ showed remarkable stability against pepsin hydrolysis treated with and without TGase. The high molecular polymers were easily hydrolyzed with digestive enzymes in vitro experiment. These results suggested that novel dairy products using TGase would have no special digestive problem in human body.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.320-324
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• 2018

Chunkookjang, fermented soybean is rich in diverse oligopeptides which derived from cleavage of soybean proteins during fermentation. Microarray data containing differently expressed genes in breast cancer cells treated with fermented soybean extract and well known breast cancer metastasis markers were combined, and a new network was constructed. It is used to check interactions between the marker proteins and the differently expressed genes. Based on the network analysis, PLAU (plasminogen activator, urokinase, uPA) and ERBB2 (epidermal growth factor receptor 2) are chosen as possible metastasis genes. We treated breast cancer MCF7 cells with fermented soybean extract and measured expression levels of PLAU and ERBB2. Fermented soybean extract suppressed PLAU and ERBB2 expressions conspicuously. In the cancer cells treated with fermented soybean extracts, an inflammation marker, NO production was also reduced. It will be interesting to find specific peptides to suppress PLAU and ERBB2 expressions in human breast cancer cells.

• Korean Journal of Food Science and Technology
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• v.51 no.5
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• pp.473-479
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• 2019

Gryllus bimaculatus (GB) has recently been registered as a food variety in Korea. In the present study, we prepared protein hydrolysates from GB and evaluated their antioxidant capacity. Protein hydrolysates were prepared from dried GB using enzymatic hydrolysis using five different proteases, and protein hydrolysates showing high hydrolysis value (alcalase, flavourzyme, and neutrase) were separated further into fractions ${\leq}3kDa$ and then lyophilized. Based on $RC_{50}$ values of hydrolysates (${\leq}3kDa$) obtained from four different antioxidant analyses, the flavourzyme hydrolysates showed relatively high levels of antioxidant capacity among the three hydrolysates, and in particular, it showed considerably strong antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The flavourzyme hydrolysate also significantly inhibited peroxidation of linoleic acid. These results suggest that protein hydrolysates from GB represent potential sources of natural antioxidants. Our current studies are focused on identification of active peptides from the flavourzyme hydrolysate.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.787-791
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• 2012

Bloods from slaughtered Korean native cattle (Hanwoo : Bos taurus coreanae) can be used in agriculture with various beneficial effects on the environment. This study was performed to find out the effect of the application of calcium and germanium, which are chelated with peptides made of cattle bloods on the absorption of them by cherry tomato (Lycopersicon esculentum Mill.). Peptide was purified by enzymatic hydrolysis and ultrafiltration from serum protein, which is composed of Asp, Glu, Lue etc. Chelated Ca and Ge were produced by reacting the peptide with $CaCl_2$ and Ge-$132^{(R)}$. Then, they were applied to cherry tomato during cultivation period at the rate of $300mL{\times}3times$ (10 days interval) for each tomato tree. Application of chelated-Ca increased the Ca contents in leaves and fruits of cherry tomato showing as 19.9% and 23.4% in newerly prepared chelated-Ca-200 ($200mg\;L^{-1}$), 8.1% and 6.8% in commecrial Calciolid Ca-300 ($300mg\;L^{-1}$) compared to 3152.6 and $63.2mg\;kg^{-1}$ in control, respectively. Application of chelated-Ge showed the increase in the germanium contents in both leaves and fruits of cherry tomato by over 6 times than those of control and over 4 times than Ge $132^{(R)}$-20 application. As a result of this study, it seemed that the application of chelated-Ca and chelated-Ge would be more effective than the existing commertial one in the absorption of calcium and germanium by cherry tomato.

• Korean Journal of Food Science and Technology
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• v.51 no.5
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• pp.480-485
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• 2019

The present study was conducted to compare antioxidant capacities of protein hydrolysates from four different edible insects (Protaetia brevitarsis larvae, Allomyrina dichotoma larvae, Gryllus bimaculatus imago, and Tenebrio molitor larvae) which have recently been registered as food varieties in Korea. Protein hydrolysates were prepared from each insect using enzymatic hydrolysis using alcalase, and were then separated into a fraction containing ${\leq}3kDa$. According to $RC_{50}$ values and trolox equivalent antioxidant capacity results obtained from five different antioxidant analyses, the Gryllus bimaculatus (GB) hydrolysate showed relatively high levels of antioxidant capacity and, in particular, the GB hydrolysate showed considerably strong antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and in ferric reducing antioxidant power (FRAP) assays. The GB hydrolysate also showed the strongest inhibitory effect on peroxidation of linoleic acid, and its rate of inhibition at $100{\mu}g/mL$ on day 3 of treatment was 60.26%. These results suggest that protein hydrolysates from edible insects including GB represent potential sources of natural antioxidants.

• 축산식품과학과 산업
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• v.9 no.2
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• pp.58-65
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• 2020

우울증은 동기, 의욕, 관심, 주의력, 정신기능 및 식욕의 감소를 특징으로 하는 일종의 기분 장애이다. 우울증은 유전적, 내분비 및 환경적 스트레스를 포함한 다양한 원인에 의해 발생하지만 가벼운 우울증은 식이요법으로 개선되는 것으로 보고되었다. 따라서 우울증 환자를 치료하기 위해서는 기능성 및 영양 보충제를 포함한 다양한 식품 공급원이 필요하다. 치즈에는 숙주 건강에 유익한 영향을 미치는 생리 활성 펩타이드가 포함되어 있다. 특히 저지(Jersey) 우유는 홀스타인(Holstein) 우유보다 고형분 함량이 높은 것으로 보고되었다. 이 연구는 저지(Jersey) 와 홀스타인(Holstein) 우유의 가우다 치즈(Gouda cheese)가 만성 스트레스(CUMS, chronic unpredictable mild stress)에 미치는 영향을 조사했다. 치즈를 먹인 만성 스트레스 마우스 모델의 개선적 변화는 젖소 종에 관계없이 통계적으로 유의미하게 효과적으로 나타났다. 흥미롭게도 PCR을 통한 분변 미생물 균총 분석에서 저지 치즈를 섭취함으로써 Bacteroidetes가 증가하고 Firmicutes가 유의적으로 감소하는 것으로 나타났다. 종합하면, 본 연구는 치즈 섭취가 스트레스 개선 작용이 있음을 제시하며, 특히 장내 미생물 균총의 유익한 방향으로의 변화가 관찰되는데, 치즈의 생리활성물질 혹은 장내미생물 균총의 대사물질들이 이러한 행동·정신학적 개선 작용과의 연관성이 있음을 시사한다.