Thermal Behavior of Soy Protein Fractions Depending on Their Preparation Methods, Individual Interactions, and Storage Conditions

Abstract

Different soy protein isolates (SPI) and whey soy protein (WSP) samples were obtained from fresh and stored soybean flour. Some samples were subjected to a long, cold storage. DSC thermograms of SPI showed the two characteristic endotherms, corresponding to denaturation of β-conglycinin and glycinin. Low value of denaturation enthalpy and high glycinin denaturation temperature were related to a reduction of protein solubility of SPI. DSC thermograms of WSP also showed two characteristic endotherms, corresponding to Kunitz trypsin inhibitor and lectin. The methods and conditions of preparation and storage of WSP samples were factors that modified their thermal behavior. Some SPI-WSP mixtures (1:1) exhibited more complex thermograms and higher denaturation temperatures. Thermograms of SPI-denatured WSP mixtures showed that the thermal stabilization of soybean storage proteins was attributed to protein-protein interactions. The differences in the thermal behavior of single or mixed SPI and WSP could not be explained on the basis of mineral content.

A comparative study of lipid and hypochlorous acid induced oxidation of soybean proteins

“…Again, the acid and basic subunits of the 11S glycinin were the most stable towards the incubation with or without oxidizing lipids at 70 C. Remarkably, protein aggregation was observed as soon as after 24 h of incubation as manifested by smearing towards the top of the gel. However, the observed aggregation was probably due to thermal degradation of the 7S conglycinin which is known to have a lower denaturation temperature compared to the 11S glycinin (Sobral, Palazolo, & Wagner, 2010). In the case of incubation with fish oil only, slightly more severe decrease of the band intensity of the 11S glycinin bands was observed in line with the previous observed modification of amino acid.…”

Relationships Between Soybean 11S Globulin Content and Thermal and Retrogradation Properties of Nonwaxy Maize Starch

“…As shown in Table I, significant differences were observed in T o I and T p I of mixtures with different soybean 11S globulin content (P < 0.05), and the T o I and T p I of mixtures showed a positive correlation with soybean 11S globulin content (r = 0.917, P < 0.01; r = 0.775, P < 0.05, respectively). However, it is different with the reaction of soybean proteins (Sobral et al 2010). Higher amounts of 11S globulin in mixtures could increase the onset and peak temperatures (T o I and T p I) of the maize starch gelatinization.…”

Influence of drying conditions on the gelling properties of the 7S and 11S soy protein fractions

“…Heat denaturation involves the breaking of intramolecular bonds, unravelling and aggregation of the protein molecules. Thus the greater number of disulphide bridges and intra and inter subunits presents in the 11S-rich fraction led to higher energy required to denature the protein fraction (Sobral et al, 2010) denaturation enthalpy. The similar values found for enthalpy under the different drying conditions, for both the 7S rich fraction and 11S rich fraction, indicated that the samples showed similar degrees of denaturation, with the exception of samples dried under the most extreme temperature (spray dried at 180 • C).…”