Influence of Heating Temperature on Conformational Changes of Soybean Proteins

Observations on the dissociation of .beta.-conglycinin into subunits by heat treatment

“…Shielding of repulsion forces among denatured 8-conglycinin resulted in a profound increase in turbidity upon heating ( Figure 1). These readily aggregating characteristics are in good agreement with previous reports (Iwabuchi and Yamauchi, 1984;Hashizume et al, 1975;Hashizume and Watanabe, 1979). Results obtained by turbidity measurements described above (Table I; Figure 1) demonstrated the fact that under the limited salt-free conditions and pH range above 7.2 a transparent solution of 8-conglycinin was obtained upon heating a t 100 "C for 5 min.…”

Molecular understanding of heat‐induced phenomena of soybean protein

“…These indicate that the release of the acidic polypeptides by heating may expose the basic polypeptide to an aqueous system. The concentration of hydrogen ions (pH 7.6) of the aqueous system (the standard buffer) used in this experiment and also by Wolf and Tamura (44), and by Hashizume et al (46) is very close to the isoelectric point of the basic polypeptide (49). Therefore, the distance among basic polypeptides may be closer, and the interchange between sulfhydryl and disulfide residues is favorable.…”

“…Heating unfolds its conformation, and both acidic and basic polypeptides may then be exposed to an aqueous system. The potential of the hydrogen ion (pH 7.6) of the aqueous system (standard buffer) used in the present experiment (48), and also in Hashizume et al (46), is much closer to the isoelectric point of the basic polypeptide (49) than that of the acidic polypeptide. Therefore, the distance among basic polypeptides may decrease (II), and interchange between sulfhydryl and disulfide residues among basic polypeptides then becomes possible (III).…”

“…Therefore, the present work, as described below, provides molecular insight using purified glycinin. (68) At low protein concentration (<0.5%), extensive studies have provided a basic knowledge of thermal denaturation of soybean glycinin (41,44,(46)(47)(48)(50)(51)(52)(53)(54)(55)(56)(57)(58), and these are considered as the basis of thermal denaturation (gelation) of glycinin at high protein concentration.…”

Effect of selective thermal denaturation of soybean proteins on soymilk viscosity and tofu's physical properties

“…The discrepancies on soybean protein denaturation temperatures in the literature were not peculiar and could be explained by different experimental and sample conditions (Lakemond, de Jongh, Hessing, Gruppen, & Voragen, 2000;Puppo & Anon, 1999;Renkema, Gruppen, & Vliet, 2002). Differences in the conformational changes by heating at the same temperature between soymilk and the acid-precipitated protein solution were observed, and these differences were attributed to the differences of ionic strength of the two solutions (Hashizume & Watanabe, 1979).…”