• Journal of Nutrition and Health
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• v.29 no.8
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• pp.861-866
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• 1996

Tannins in plant foods and beverages may produce antinutritional or toxic effects although some proteins with high affinity for tannins seem to function as defense mechanism to tannin toxicity. Our objectives were to investigate of tea tannins, iron and protein and to evaluate the role of proteins in tannin effects on iron solubility. Iron solubility in vitro was measured using tea with and without proteins. Mixtures of tea, protein in varying concentrations(either gelatin or bovine serum albumin), and iron(eithe 10 or 50ug/mL) were prepared. Controls contained water in place of tea. Iron bioavailability was assessed by measuring iron solubility in the simulated gastric condition with pepsin digestion. Bound iron was removed by centrifugation and soluble in tea alone. When iron concentratin was 10ug/mL, addition of small amounts of protein to tea dramatically reduced iron solubility, but solubility of iron increased in the tea mixturea as the concentration of protein was increased. The percnetage of iron that precipitated was much greater at 10ug Fe/mL than the values at 50ug Fe/mL suggesting that the iron binding sites on the tea-protein complex was saturated. These results suggest that interactions of iron with tea tannins are influenced by the concentratins of protein and iron.

• Korean Journal of Food Science and Technology
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• v.22 no.3
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• pp.343-349
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• 1990

The solubility of protein and phytate was measured at various pH's in distilled water and at various concentrations of NaCl, $CaCl_2\;and\;Na_2SO_3$ solutions, and then optimum condition for producing low phytate protein isolate from perilla flour was investigated. The protein solubility in water showed minimum at pH 4.0 and increased at pH higher or lower than 4.0, while phytate solubility was highest at pH 5.0 and decreased at pH higher or lower than 5.0. In NaCl solution, protein solubility was lowest between pH 3.0-4.0, while phytate solubility was high between pH 2.0-5.0 and abruptly decreased above PH 6.0. In $Na_2SO_3$ solution, protein solubility was lowest between pH 2.0-3.0 and phytate solubility showed maximum values between pH $5.0{\sim}6.0$, and it's solubility was low in 3% salt concentration at all pH ranges. In $CaCl_2$ solution, protein solubility in 3% salt concentration was relatively low at all pH ranges, and phytate solubility showed highest values between pH $2.0{\sim}3.0$ and abruptly decreased (1.0%) above pH 4.0. In order to make low phytate protein isolate, defatted perilla flour protein was extracted at pH9.0 and precipitated at pH 4.0 in 3% NaCl solution. The yield of low phytate protein isolate was 61.4% of total protein. This protein was found to contain 0.02% phytate by weight.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.8
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• pp.1159-1165
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• 2016

The nutritional value of feed proteins and their utilization by livestock are related not only to the chemical composition but also to the structure of feed proteins, but few studies thus far have investigated the relationship between the structure of feed proteins and their solubility as well as digestibility in monogastric animals. To address this question we analyzed soybean meal, fish meal, corn distiller's dried grains with solubles, corn gluten meal, and feather meal by Fourier transform infrared (FTIR) spectroscopy to determine the protein molecular spectral band characteristics for amides I and II as well as ${\alpha}$-helices and ${\beta}$-sheets and their ratios. Protein solubility and in vitro digestibility were measured with the Kjeldahl method using 0.2% KOH solution and the pepsin-pancreatin two-step enzymatic method, respectively. We found that all measured spectral band intensities (height and area) of feed proteins were correlated with their the in vitro digestibility and solubility ($p{\leq}0.003$); moreover, the relatively quantitative amounts of ${\alpha}$-helices, random coils, and ${\alpha}$-helix to ${\beta}$-sheet ratio in protein secondary structures were positively correlated with protein in vitro digestibility and solubility ($p{\leq}0.004$). On the other hand, the percentage of ${\beta}$-sheet structures was negatively correlated with protein in vitro digestibility (p<0.001) and solubility (p = 0.002). These results demonstrate that the molecular structure characteristics of feed proteins are closely related to their in vitro digestibility at 28 h and solubility. Furthermore, the ${\alpha}$-helix-to-${\beta}$-sheet ratio can be used to predict the nutritional value of feed proteins.

• Journal of the Korean Home Economics Association
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• v.28 no.2
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• pp.37-45
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• 1990

The purpose of this study was to determine the foaming properties of two small red bean protein isolates at various conditions. Data concerning the effects of pH, temperature, MaCl concentration, sugar concentration and protein concentration on the properties such as solubility, foam expansion, foam stability were presented. The results were summarized as follows : 1. The crude protein contents of two small red beans were 26.14% and 22.71%. The percentage of nonpolar amino acid group was the highest and that of sulfur containing amino acid group was the lowest. 2. Protein solubility showed the minimum at pH 4.5 which is isoelectric point of small red bean protein isolate adn heat treatment lowered solubility(P<0.05). At pH 4.5, solubility increased sighificantly as 0.4M NaCl was added. However, the effect of sugar concentration in the solubility was not significant. 3. Foam expansion of two small red bean protein isolates was high at pH 4.5 and heat treatment at 10$0^{\circ}C$ lowered foam expansion(P<0.05). While addition of NaCl, sugar did not affect the foma expansion, gradual increment of the protein isolates concentration up to 9% decreased the foma expansion slightly. 4. Foam stability was significantly high at pH 4.5 and heat treatment at 10$0^{\circ}C$ lowered foam stability. Addition of sugar caused slight decrease in foam stability. From 1% to 9% suspension, foma stability increased significantly as protein concentration increased(P<0.05)

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.769-773
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• 2001

Protein content of okara and soybean were found to be 37.3% and 42.5%, respectively by micro-Kjeldahl analysis. Solubility of okara protein in phosphate buffer (pH 8) was 10% versus soy protein of 68.4%. Insolubilization of okara protein was mostly due to disulfide bonding between cysteine residues caused by excessive heat treatment during soymilk processing: hydrophobic interactions and hydrogen bondings were involved to lesser extent. Optimum extraction temperature and time were $60^{\circ}C$ and 40 min. Typical solubility profile of soy protein disappeared for okara protein though minimum solubility of the protein was around pH 3.0. Treating okara with protease was effective in solubilizing okara protein and solubility increased to 19.2%. Optimum reaction temperature and time were $80^{\circ}C$ and 50 min, respectively. Cell wall degrading enzyme did not increase solubility of the protein, however. Through enzymatic reaction okara protein could be effectively solubilized for uses as food ingredient.

• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.279-283
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• 1992

This study was undertaken to investigate the effects of added phytate and pH on the solubility and in vitro digestibility of low-phytate rapeseed protein isolate. Phytate content of low-phytate rapeseed protein isolate was 1.5%, as a result of 66% removal from defatted rapeseed flour and the protein: phytate ratio was 58:1. Solubility of rapeseed protein isolate at pH 2.0 and pH 11.5 was much higher than near the isoelectric point, pH 5.0. It's solubility was lowered by adding an increased amount of phytate especially at pH 2.0. The inhibitory effect of phytate toward pepsin digestibility of rapeseed protein isolate decreased by the increasing amount of phytate added. It is suggested that the production of low-phytate rapeseed protein isolate is necessary to improve the functionality and nutritional value in order to utilize it as food material.

• Food Science of Animal Resources
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• v.21 no.3
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• pp.192-199
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• 2001

The objective of this study was to investigate the effects of hot- and cold-boning on sarcomere length, drip loss and protein solubility of post-rigor porcine longissimus muscle. A total of ten pigs(borrow, 100$\pm$5 kg) were randomly selected at a commercial plant and the carcasses were split in half after slaughter. The longissimus muscle of the left side was dissected and chilled at 0$^{\circ}C$ after trimming of subcutaneous fat whereas the right side carcasses were served for cold-boning after chilling for 24 hrs. The temperature, pH and sarcomere length of porcine longissimus muscle were measured at postmortem 1, 3, 6, 12 and 24 hours. Drip loss, cooking loss, Minolta L*a*b*, shear force and protein solubility were measured at postmortem 24 hrs. The pH of cold-boning samples was rapidly decreased whereas temperature and sarcomere length of hot-boning samples were rapidly decreased during 24 hrs of chilling. Hot-boning muscles showed significantly (P<0.05) higher pHu and shorter sarcomere compared with cold boning muscles because of cold shortening. However, there were no significant differences in drip loss, cooking loss and shear force value between hot- and cold boned samples. The samples of hot-boning showed lower Minolta L* value and higher sarcoplasmic protein solubility compared with cold boned samples. These results suggest that the pale color changing of porcine longissimus muscle could be inhibited by hot-boning due to rapid chilling of the muscle although sarcomere length could be shortened because of cold shortening. Also these results show that hot-boning of porcine carcass could have a high protein solubility without negative effects of drip loss or tenderness of porcine longissimus muscle.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.5
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• pp.811-815
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• 1995

Effect of deamidation with Neutrase on the solubility of bovin serum albumin(BSA), egg albumin(EA), soy protein isolate(SPI) was investigated. Solubility of deamidated BSA in distilled water was decreased from 98% to 83% against native BSA at pH 4~8, minimum solubility of deamidated BSA was pH 6. Solubilities of native BSA and deamidated BSA in 0.2M NaCl solution were shown 100% as compared greately decreasing both solubilities in 1.0M NaCl at acidic pH. According to deamidation, solubility of EA in distilled water was increased below pH 4 and above pH 6, while solubility of EA in NaCl solution was decreased by deamidation at acidic pH. Solubility of SPI in distilled water was greately increased by deamidation at overall pH, deamidation was increased solubility in NaCl solution above pH 5. There was, however, no difference on solubility by deamidation below pH 5.

• Food Science of Animal Resources
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• v.23 no.1
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• pp.63-69
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• 2003

This experiment was carried out to study changes in solubility and emulsifying properties of whey protein. Whey protein hydrolysates were obtained from tryptic hydrolysis of whey protein concentrate at pH 8.0 and 37$^{\circ}C$ for 6 hours. Emulsifying activity of whey protein hydrolysate was highest at 4 hours of hydroysis and at 5.50% of DH. During hydrolysis of whey protein concentrate with trypsin, ${\alpha}$-lactalbumin was not easily broken down. But ${\beta}$-lactoglobulin was hydrolysed rapidly from the early stage of hydrolysis, producing several low molecular weight peptides, which have to participate in increasing emusifying activity. The solulbility of hydyolysates tended to increase depending on hydrolysis time; however, there was a gradual decrease after 5 hours. The hydrolysate had a minimum solubility near the isoelectric point range (pH 4∼5). The more hydrolysed the whey protein concentrates, the more soluble they are near the pl. They aye also more soluble above pH 6. Emulsifying activity of hydrolysates showed similar results to solubility. Creaming stability gradually increased when hydrolysis increased, increasing rapidly above pH 8 after 4 hours of hydrolysis.

• Korean journal of food and cookery science
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• v.9 no.4
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• pp.278-283
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• 1993

This study was attempted to investigate the effects of enzymatic modification of milk protein with protease on functional properties. The selected functional properties were solubility, emulsifying activity (EA), emulsion stability(ES), foam expansion(FE), and foam stability(FS). These properties were measu-red from pH 3.0 to pH 8.0. The proteases used in this study were iaolated from Meju(fermemted soybean) and had specific activity of 250 units/㎎ protein at pH 7.0, 1600 units of pretense was used for 1gr. of skim milk protein. Skim milk showed 30.5％ degree of hydrolysis for 1 hr. and 36.4% degree of hydrolysis for 3.5 hrs. of protease treatment at pH 7.0. Solubility of native skim milk, control, 1 hr. and 3.5 hrs. groups were 3.37, 3.64, 10.21, 14.34％o at pH 4.0 respcetively. The emulsifying activity of native skim milk, control, 1 hr. and 3.5 hrs. groups were 38.8,42.0,43.0,46.7ft at pH 4.0, respectively. Enzymatic modification resulted in the increase of solubility and emulsifying activity at pH 4.0. However at pH 5.0 emulsifying activity of 1 hr. and 3.5 hr. group were lower than native skim milk and control groups. 1 hr. protease treatment was found to be most effective way of increasing foam expansion at pH 4.0 to 6.0. It was supported that, protease treated skim milk can be used to improve solubility, emulsifying activity, foam expansion at acid pH. meju protease. skim milk, solubility, emulsion, foam.