Study On Glycosylation Modification Of Soy Protein Isolate And Its Gel Properties

Soy protein is a high quality plant protein source and has many important functional properties in foods,such as solubility,foaming,emulsifying,antioxidant,gelation and water holding.Among the functional properties of soy protein,gelation plays an important role,which directly affects the quality of soy protein products.Glycosylation modification of soy protein isolate(SPI)could obtain more excellent functional properties.In this paper,the SPI was used as the raw material,and the reducing sugars with different molecular sizes were used as the glycosylation reaction object.Using biochemistry,enzymology,protein chemistry,spectroscopy and rheology,the effects of small molecule sugar and polysaccharide glycosylation on the structure and functional properties of soy protein isolate(SPI)were investigated.Study on the structure and function of SPI by different molecular size sugars,including solubility,surface hydrophobicity,rheology,etc.Analysis of the effects of glycosylation modification of different sugars and SPI on the structure of soy protein isolate,such as secondary(?-helix,?-sheet,?-turn);analysis of MTG enzyme cross-linked glycosylated SPI the action mechanism of gel formation process,exploring the formation mechanism of MTG enzyme cross-linked glycosylated SPI gel,and determinating the glycosylated SPI by studying the mechanism of protease gelation of maltodextrin and SPI gel rheological properties,microstructure.The main conclusions are as follows:(1)Glycosylation of SPI by glucose,fructose,maltose and lactose could significantly improve the structural and functional properties of SPI.The glycosylation of glucose,fructose,maltose and lactose with SPI both improved the solubility,surface hydrophobicity and secondary structure of SPI and improved the rheological properties of the gel.The secondary structure analysis of infrared spectrum showed that the glycosylation treatment reduced the content of ?-helix,?-turn and random coil structure of protein and increased the content of ?-sheet structure.Among the four small molecular sugars,maltose has the most obvious effect on the modification of soy protein isolate,followed by glucose,fructose and lactose.(2)Glycosylation of SPI with polysaccharide significantly improved the structural and functional properties of SPI.After the glycosylation of maltodextrin,dextran,chitosan and xanthan gum with SPI,the solubility,surface hydrophobicity and secondary structure of SPI were significantly improved,and gel rheology features have also been improved.The secondary structure was studied by infrared spectroscopy.The results showed that the content of ?-helix,?-turn and random coil structure of protein decreased slightly after glycosylation,and the content of ?-sheet structure increased slightly.Among the four polysaccharides,the most obvious effect on the glycosylation modification of SPI was maltodextrin,followed by dextran,chitosan and xanthan gum.(3)The structural properties of the MTG-induced SPI-MD gel were investigated.SDS-PAGE analysis confirmed that glycosylation had occurred.Glycosylation could improve the solubility,rheology and gelation of soy protein isolates.The experimental results show that the gel strength,storage modulus(G'),loss modulus(G")and water holding capacity are improved to form a denser and more uniform MTG-induced SPI-MD gel network.There is a correlation between these factors.In addition,based on infrared spectroscopy,we found that glycosylation changed the secondary structure of the gel sample,?-helix,?-turn,random curl content,and ?-sheet content increased.These results indicated that glycosylation promotes cross-linking of MTG by altering protein structure.Therefore,glycosylation could promote gelation of MTG-induced SPI-MD gel and expand its application in the food protein gel industry.