Enhancing The Foaming And Emulsifying Properties Of Soybean Protein Isolate By Enzymatic Modification

Soybean protein is not only an important protein source for human nutrition but also an industrial material with low price and low cholesterol level. However, its poor functionality limited its used in the food industry. For example, its foaming property is far worse than egg white protein. In this study, the influence of enzyme modification on the structure and functionality such as foaming property of soybean protein isolate was investigated。SPI was hydrolyzed by alcalase, then the different molecular weight hydrolysates (MW<5kDa and MW>10kDa) were separated by ultrafiltration. Subsequently, the hydrolysates with proper molecular weights were cross-linked by TGase. In conclusion: the foaming capacity and foaming stability were improved significantly after the enzyme modification; the emulsifying activity was improved significantly but the emulsion stability was depressed.Then the enzyme modification on the foam properties and the emulsifying properties of SPI was researched from the view of the hydrophilic-hydrophobic properties. The hydrophilic peptides and the hydrophobic were separated and cross-linked by TGase on different combination, then the foam properties and the emulsifying properties were measured. The results were the foam capacity and foam stability were improved but the emulsifying activity and the emulsion stability were depressed, this results were related to the change of the surface hydrophobicity and the content of amino group.The structural properties (solubility, surface hydrophobicity, surface tension, the content of amino group,the distribution of molecular weight), the foam properties and the emulsifying properties were measured and be compared with the original SPI. the foam properties had obvious connection with solubility, surface hydrophobicity, surface tension and the distribution of molecular weight.The relationship between the structural properties and foam properties and the emulsifying properties: the larger the molecular weight was, the better the foam stability and the emulsifying activity were; the higher the NSI was ,the better the foam capacity was; the lower the surface tension was, the better the emulsifying activity was; the more the free amino groups was, the foam stability and the emulsion stability were.The research is meaningful to the structure modification and widely application of soybean protein isolate.