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COMPARATIVE STUDY OF STRUCTURAL CHARACTERISTICS AND THERMAL BEHAVIOR OF WHEY AND ISOLATE SOYBEAN PROTEINS
Author(s) -
SORGENTINI DELIA A.,
WAGNER JORGE R.
Publication year - 1999
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1999.tb00033.x
Subject(s) - chemistry , differential scanning calorimetry , ionic strength , thermal stability , soy protein , electrophoresis , trypsin , denaturation (fissile materials) , hydrophobic effect , lectin , chromatography , soybean proteins , food science , enzyme , crystallography , biochemistry , nuclear chemistry , organic chemistry , physics , aqueous solution , thermodynamics
Electrophoretic profiles, sulfhydryl(SH)/disulfide (SS) groups content, and surface hydrophobicity (H 0 ) values of whey soybean proteins (WSP) and native soy isolates (NSI) were determined. WSP, composed mainly by Kunitz trypsin inhibitor (KTI), and lectin (L), has a H 0 value of 24.0 ± 1.0, which is 6.8 times lower than that of NSI ones, and SH/SS groups content in the same range of NSI. The thermal behavior of WSP and NSI was studied by differential scanning calorimetry (DSC). The WSP thermogram in water, similar to NSI, showed two main peaks (Tp values: 74.0 ± 0.5 C and 90.4 ± 0.8C) attributed to thermal denaturation of KTI and L, respectively. These endotherms are slightly affected by μ, whereas those of NSI are strongly affected (Tp of 7S and 11S peaks increase 17C and 20C respectively, by increasing NaCl concentration from 0 to 1M). WSP has low Ho values not noticeably affected by ionic strength changes, whereas NSI has higher Ho, that increase in saline media and favor intermolecular hydrophobic interactions. The consequent low tendency to protein aggregation by hydrophobic interactions in WSP would explain their lower thermal stability at high μ. Control proteins of both preparations (7S and 11S enriched fractions for NSI, and purified trypsin inhibitors, urease and lectin for WSP) were use to confirm these results.