Gelation Property of Alcohol-Extracted Soy Protein Isolate and Effects of Various Reagents on the Firmness of Heat-Induced Gels

Abstract

Gelation property, thermal property, protein subunits distribution, and molecular forces involved in gelation of alcohol-extracted soy protein isolate were investigated using texture analyzer, differential scanning calorimeter, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and various reagents. Results showed that salts and pH played important roles in gel firmness, and a power law relationship between gel firmness and protein concentration was observed. The effects of various reagents revealed that disulfide bonds play a major role in soy protein gel formation, while the involvement of electrostatic interactions, hydrogen bonds, and/or hydrophobic interactions also occurred in gel networks. Thermal analysis indicated that both alcohol-extracted soy protein isolate and commercial soy protein isolate (isoelectric precipitation) have undergone serious denaturation, while the gel firmness of alcohol-extracted soy protein isolate was significantly greater than that of commercial soy protein isolate. Sodium dodecyl sulfate polyacrylamide gel electrophoresis image showed that there was almost no difference for protein subunits among alcohol-extracted soy protein isolate, commercial soy protein isolate, and soy powder. Hence, as an alternative environmental friendly extraction method, alcohol-extraction of soy protein isolate has a great prospect to replace presently applied isoelectric precipitation method.

Modification of rice protein with glutaminase for improved structural and sensory properties

“…Urea can influence the hydration properties of the protein and also weaken or break down hydrophobic interactions by forming hydrogen bonds to exposed amide groups on the protein (Zhang & Cremer, ; Shan et al ., ). To investigate the possible molecular interactions during rice protein aggregation, the untreated rice protein and treated rice protein were dissolved in 6 mol L −1 urea solution to interrupt hydrophobic interactions before the particle size was determined.…”

“…In this study, the D[3,2] and D [4,3] values of the treated rice protein were closer than those for the untreated rice protein, indicating that enzymatic deamidation had a certain effect on particle shape and made rice protein particles more regular. Urea can influence the hydration properties of the protein and also weaken or break down hydrophobic interactions by forming hydrogen bonds to exposed amide groups on the protein (Zhang & Cremer, 2010;Shan et al, 2014). To investigate the possible molecular interactions during rice protein aggregation, the untreated rice protein and treated rice protein were dissolved in 6 mol L À1 urea solution to interrupt hydrophobic interactions before the particle size was Data are presented as mean AE standard deviation (SD) and different superscript letters in the same column indicated significant differences (P < 0.05).…”

Addition of Salt Ions before Spraying Improves Heat- and Cold-Induced Gel Properties of Soy Protein Isolate (SPI)

“…These results may be due to the functional groups buried in the protein matrix becoming sufficiently exposed to improve the interactions between the protein molecules at low ionic strength; Ca 2+ , Mg 2+ , and Na + ions could bind negatively charged groups on the protein molecules, which leads to conformational changes that make more hydrophobic groups available at the surface [40]. Thus, the hydrophobic interactions and disulfide interactions were increased at low ion concentrations, while the high ionic strength resulted in salting-out as previously discussed, thus affecting the gelation of the protein [41]. Therefore, hydrophobic interactions and disulfide bonds were reduced at high ion concentrations (0.01-0.015 M).…”

Effects of NaCl and soy protein isolate on the physicochemical, water distribution, and mobility in frankfurters

“…Chen et al (2017) showed that NaCl supplementation (2 mol L À1 or 4 mol L À1 ) led to faster aggregation and gelation, and the particle size and weight of the aggregate increased with the increase of NaCl content. Shan et al (2015) found the highest SPI gel firmness value at 0.5 mol L À1 NaCl, and that higher-level gel firmness values could be detected at NaCl concentrations between 0.2 and 0.6 mol L À1 . To the best of our knowledge, few researches have focused on the effect of NaCl and SPI in reduced-salt emulsified meat products.…”

“…Gao et al (2015) found that the cooking yields of all pork batters with SPI were higher, indicating that SPI effectively participated in water and fat retention during heating. Another reason is that the SPI gel properties were affected by salt, and the gel strength increased at adequate NaCl concentrations (0.3 À0.6 moL L À1 ) (Shan et al, 2015).…”