• Applied Biological Chemistry
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• v.37 no.5
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• pp.379-384
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• 1994

Casein or soybean protein was subjected to the reaction with caffeic acid-tyrosinase system at $30{\sim}35^{\circ}C$ pH 6.8 with aeration for 5 hr. The effects of the modified proteins on male Wistar rats were studied by pair-feeding of a cholesterol-free diet for 2 weeks. Significant decrease in protein digestibility for the rats fed with the modified proteins was observed. The feeding of modified protein from casein caused an enlargement of caecum. The concentration of serum cholesterol and triglyceride in the rats fed with modified proteins were mostly unchanged against the rats fed with untreated proteins. These results suggest that the decrease in protein digestibility induced by enzymic browning-reaction did not cause the decrease in concentration of serum cholesterol.

• Food Science of Animal Resources
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• v.29 no.6
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• pp.659-667
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• 2009

Casein is considered to be the main source of protein in milk; therefore, many studies have been conducted to identify casein-derived bioactive peptides and their physiological effects. Casein is inactive within the parent protein but can be liberated by various proteases and enzymatic hydrolysis during microbial fermentation and gastrointestinal digestion. Once absorbed, casein exhibits different bioavailabilities in the body. Specifically, casein-derived peptides function as angiotensin converting enzyme (ACE) inhibitor in the cardiovascular system; thus, they are expected to reduce and prevent hypertension. Additionally, casein-derived peptides behave as opioid-like peptides in the nervous system, which impacts relaxation. These peptides are also expected to modulate various aspects of immune functions. Finally, caseinophosphopeptide (CPP) and glycomacropeptide (GMP) may exhibit a number of nutritional effects such as the absorption of calcium, iron or zinc. Many studies have been conducted to evaluate casein-derived peptides due to their multifunctional properties and the results of these studies have contributed to the development of a wide variety of functional dairy products. The purpose of this paper was to review the generation of bioactive peptides, their absorption and metabolism, and their specific bioactive effects.

• 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 Food Science and Technology
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• v.30 no.5
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• pp.1035-1039
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• 1998

Phase separation is the typical phenomenon in protein-polysaccharide mixtures because of thermodynamic incompatibility between two macromolecules. Phase separations of casein-alginate-water systems were investigated by using phase diagram under varying pH (6, 8 and 10) and NaCl concentrations (0, 0.25 and 0.5 M). Incompatibility decreased with increasing pH and decreasing NaCl concentration. Molecular weight of alginates did not significantly affect the phase diagram of casein-alginate-water systems. The results strongly suggested that compatibility of casein and alginate involved electrostatic interactions.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.21 no.1
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• pp.53-66
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• 1995

The gene for ${\gamma}$-casein, a milk protein, is a member of a family of casein gene which is expressed in mammary glands of the animal during the late gestation and lactation periods binder the influence of various hormones. In order to elucidate tile mechanisms b)'which hormones regulate the coordinate induction of milk protein genes, the mouse ${\gamma}$-casein gene was isolated and characterized. The ${\gamma}$-casein gene was screened from a mouse genomic library constructed in bacteriophage EMBL3 with the ${\gamma}$-casein CDNA used as probe and one clone was obtained. The ${\gamma}$-casein CDNA as probe was partially sequenced and contained ATG start codon and 5'-noncoding region. The cloned genomic DNA was digested with Sal I restriction enzyme, by which the insert DNA can be isolated from EMBL3 vector. Three DNA bands were observed and the size of DNAs was approximately 28kb, 14kb and 9Kb, respectively Accordingly the size of the insert DNA was calculated with approximately 23Kb. The result of Southern blot analysis, however, showed that the cloned genomic DNA was not hybridized with the synthetic oligonucleotides (40 mer) of cDNA 5'-end region, but it was hybridized with the y -casein CDNA. This means that tile cloned y -casein gene may not contain its promoter region. The ${\gamma}$ -casein genomic DNA containing the promoter region has been screening from mouse genomic library with oligonucleotides of CDNA 5'-end region as probe, and twenty-nine clones was obtained.

• Journal of Aquaculture
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• v.10 no.1
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• pp.77-85
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• 1997

A 6-week feeding trial was conducted to determine the nutritional value of various dietary animal protein sources in juvenile Koran rockfish. White fish meal (WFM), flounder muscle meal (FMM), blood meal (BM), casein & gelain (CG), egg white albumin (EWA) and squid liver powder (SLP) were used as the animal protein sources, Crude protein content and available energy of the experimental diets were 50% and 15.9 kJ/g, respectively. There were significant differences among all dietary groups in weight gain (WG), feed efficiency (FE), and protein effiency ratio (PER). WFM and FFM were the best animal protein sources among the dietary groups. FMM diet had significantly higher (P<0.05) WG, FE, and PER values than those of fish fed the WFM diet. WG, FE, PER, and specific growth rate (SGR) values of fish fed BM diet were significantly higher (P<0.05) than those of fish fed EWA diet. Significant differences were found in whole body composition, hemoglobin (Hb), hepatosomatic index (HSI), and hematocrit (Ht). These results showed that low-temperature processing of lyophilized flounder muscle meal resulted in superior performance of rockfish relative to the other evaluated animal protein sources.

• Food Science of Animal Resources
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• v.23 no.4
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• pp.350-355
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• 2003

Raw skim milk and colloidal calcium phosphate-free skim milk were treated with microbial transglutaminase (TGase), ultracentrifuged at varying rates and were observed to contain textural properties using a scanning electron microscope (SEM). Skim milk showed irregular signs of conformation at lower centrifugal rate, and associated regular (10,000 ${\times}$g) and thin with broad holes (20,000 ${\times}$g). The associated texture became thick and irregular (40,000 ${\times}$g), and fine particles were regularly associated (100,000 ${\times}$g). When skim milk was incubated for 1 hr with TGase, casein micelles aggregated and broadened as centrifugation rate increased. When skim milk was incubated for 8 hrs with TGase, casein micelles associated to large widened aggregates, and were associated regularly which then became irregular (100,000 ${\times}$g). When colloidal calcium phosphate-free skim milk incubated for 1 hr with TGase showed no sediment, the milk incubated for 8 hrs with TGase associated together, yielding broadened and regular layers as the centrifugation rate increased. It is assumed that such phenomena could be caused by protein crosslinking reaction with TGase and conformational change of casein molecules, as well as dependencies on reaction time, temperature and ultracentrifugation rate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.8
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• pp.1359-1366
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• 2004

Ultra high temperature treated (UHT) skim milk and colloidal calcium phosphate-free skim milk were treated with microbial transglutaminase (TGase), ultracentrifuged at various rates, lyophilized, and observed for morphological properties with a scanning electron microscope (SEM). UHT skim milk showed small holes of associated micelles at lower centrifugal rates, and became thick and irregular, and fine particles were associated regularly at higher centrifugal rates. When UHT skim milk with TGase was incubated for 1 hour, casein micelles aggregated and broadened as centrifugation rate increased. When UHT skim milk with TGase was incubated for 8 hours, casein micelles were associated irregularly to large aggregates and widened. Colloidal calcium phosphate-free skim milk with TGase incubated for 1 hour and separated by two-step centrifugation showed aggregated lump, while the milk incubated for 8 hours with TGase was associated with broadened, compact, and regular layers as the centrifugation rate increased. Such phenomena were caused by heat treatment, protein crosslinking reaction catalyzed by TGase and conformational changes of casein molecules, and could be dependent on reaction time, temperature and ultracentrifugation rate.

• Korean Journal of Food Science and Technology
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• v.12 no.4
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• pp.263-271
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• 1980

Detoxified and deallergenized castor bean protein isolate was prepared from defatted castor bean pomace for use in animal feedstuffs and human foods. Succinylation and acetylation of the ${\varepsilon}-amino$ groups of the protein improved markedly the water solubility of the protein at $pH\;7{\sim}8$. The results of the amino acid analysis of the protein isolate revealed that the sulfur-containing amino acids and L-lysine were limiting amino acids and that succinylation and acetylation caused some little loss of the amino acid content. The L-methionine enriched plastein was synthesized from the protein isolate or the acylated protein isolates and DL-methionine ethyl ester by one step process with papain. By this method the extent of incorporation of L-methionine was about 50%. Pepsin hydrolyzed both unmodified and modified protein isolates at the same rate (about 92%). Tryptic hydrolysis, however, was less for the succinylated protein isolates (about 42%) and less for the acetylated protein isolates (about 26%). The protein efficiency ratio of L-methionine enriched protein isolate (about 2.5 weight %) was 90% that of reference casein. The protein efficiency ratio values of succinylated (88%) and acetylated (84%) protein isolate were 55 and 69% of reference casein, respectively.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1433-1436
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• 2000

The effect of addition of pectin on the stability of casein solution was studied to apply casein-pectin mixture to apple juice. The solubility of 0.1% casein solution was below 20% at pH 3-5. However, the solubility of 0.1% casein-0.1% pectin mixtures was over 70% at pH 2-10. The increase in the concentration of casein-pectin mixture showed adverse effect on the solubility. The apple juice (pH 3.4), containing 0.1-0.5% casein-pectin mixtures, remained stable without the precipitation of casein. The stability of apple juice including casein-pectin mixture was maintained upon heating at $100^{\circ}C$ for 10 minutes or refrigerating for a week. This study suggested the possibility of protein fortification to acidic beverages since casein-pectin mixture maintained stability in apple juice.