Upon heating at +**, microbial transglutaminase (MTG) suppressed coagulation of whey protein concentrate (WPC) solution, decreasing solubility and increasing viscosity, particularly with addition of-* units of MTG. Creep testing of the gel prepared by treating freeze-dried WPC with +* units of MTG showed that the WPC gels decreased in instant elasticity E* and that the ratio of Newtonian viscosity, hN, for E* increased. WPC gels treated with MTG increased their water-holding capacity. In MTG treatment of WPC solution, low crosslinkage was observed at high concentration and at low pH. These observations are assumed to be due to the molecular structure of the WPC῍ It is suggested that heat tolerance is conferred on the WPC with treatment by MTG, and that this property seems to arise due to crosslinking between a-lactalbumin and b-lactoglobulin, two main milk proteins.
On the dependence of frequency for viscoelasticity, soy protein dispersion showed structural viscosity. Soy protein dispersion at pH 0.1 and pH 3.2 showed weaker conformation of protein molecules for shear than that at pH +,.*. It assumed that the weak conformation of soy protein molecules at pH 0.1 and pH 3.2 was due to the grobular stage without attraction among molecules. Based on the relationship between protein concentration and log G῏ and log h῏, protein dispersion at pH 0.1 showed the curve with upper salience, on the other hand, that at pH +,.* showed the curve with lower salience. h῏/G῏ ratio showed the peak at about pH 3./, and showed that the unholding of protein molecules was in maximum in this pH. h῏/G῏ ratio showed about +.. (w*.+ Hz) at pH +,.*. In summary, for good spinning of soy protein dispersion, it was suggested that the h῏/G῏ ratio was about +.. (w*.+ Hz), and the curve need to be lower salience in the relationships between protein concentration and log G῏ and log h῏.
The e#ect of peptides on the physical properties of soy protein gel treated with MTG were studied by breaking test and creep test. According to the addition of polylysine (PL), elasticity (E*) and Newtonian viscosity (h N) increased, and retardation (t+) decreased. On the other hand, on the addition of glutamine peptide (GP), the soy protein gel was increased on h N and t+. Namely, MTG-treated soy protein gel increased in elasticity by addition of PL, and increased in viscosity by addition of GP. By addition of peptides of wheat protein (GL) and soy protein (SP), the MTG-treated soy protein gel increased in h N and t+ according to the increasing of the dosage. Especially, the addition of GP and GL-* were e#ective on increasing of viscosity for MTG-treated soy protein gel.
῍῍῍῍῍῍῍῍῍῍῍῍῍῍῍῍By applying the correlation diagrams of instant elasticity E* and constant viscosity hN of the creep parameter, the physical properties within di#erent types of gel-type processed foods can be determined. In sausage, E, decreased, and hN remained unchanged by cooking. Regarding the relationships between creep parameter and sensory evaluation score, the texture preference of sausage before cooking correlated with elasticity E, (r̮*.0+3). On the other hand, the texture preference of sausage after cooking highly correlated with retardation time, t (t+̮*.3+1, t,̮*.221).(Received Mar. ++, ,**/ ; Accepted Jul. ,/, ,**/)̯Q̰῾ῷ̲̲̳῎QQ̰Q̯ῥῌ ῼ̯ +ῑ ̰`ῲῧΌQ ̰`Qῠῧ ῩῨ̰QQῶQQ̰Qῠ̰ῴ̰`ῢῥQῩ
On the production of restructured meat using microbial transglutaminase (MTG), there was the report that meat cubes showed acceptable binding in combination with MTG and caseinate. The acceptability of food proteins except of caseinate was studied for binding sausage pieces by MTG, and the mechanism of binding was investigated. By optimizing the volume of water added for food proteins, not only caseinate but also gelatin and soy protein showed e#ective binding by MTG. The amount of e-(g-glutamyl)lysine linkage in binding surface of sausage was contributed to binding strength. The amount of the crosslinkage in bound sausage pieces was just-῏1/ ῎mol, on the other hand,-,*῏2.0 ῎mol in glue paste. Tight binding was obtained by binding the adhesive surfaces of sausage. Based on the examination by microscope, it was suggested that glue paste permeated into a narrow space of binding surface of sausage, and gelled by MTG afterwards.
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