FOOD SCIENCE ›› 2020, Vol. 41 ›› Issue (19): 74-82.doi: 10.7506/spkx1002-6630-20191006-006

• Basic Research • Previous Articles     Next Articles

Preparation and Properties of Enzymatic Glycosylation Products of Casein with Soluble Soybean Polysaccharide

LIU Yuqi, QIN Xiaoli, KAN Jianquan, ZHONG Jinfeng   

  1. (College of Food Science, Southwest University, Chongqing 400715, China)
  • Online:2020-10-15 Published:2020-10-23

Abstract: The present work investigated the impact of mass ratio of casein to soluble soybean polysaccharide and transglutaminase concentration on the physicochemical and structural properties functionalities of conjugates formed between casein and soluble soybean polysaccharide, through the determination of various physicochemical indicators, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, Fourier transform infrared spectroscopy (FTIR) analysis, endogenous fluorescence spectroscopy (EFS) analysis and scanning electron microscope (SEM) observation. When the mass ratio of casein to soluble soybean polysaccharide was 1:1 and the transglutaminase concentration was 5 U/g, a high degree of glycosylation was obtained as evidenced by a browning index of 0.542, intermediate content of 0.907, and grafting degree of 19.9%. The physicochemical properties of the cross-linked product were improved compared with those of casein, the solubility increasing from 47.2% to 67.0%, the emulsifying activity from 116 to 123 m2/g, and the emulsion stability from 16.9 to 37.6 min. The results of SDS-PAGE and FTIRS indicated that soluble soybean polysaccharide was successfully grafted to casein. EFS analysis showed the degree of cross-linking and protein structural changes after cross-linking. The results of SEM suggested that the cross-linked product exhibited a non-homogeneous and loose porous network microstructure. Additionally, when applied to prepare oil-in-water emulsions, the cross-linked product imparted higher surface charge and stronger steric hindrance to emulsion droplets than casein, thereby stabilizing the emulsion droplets against environmental stresses. The results from this study are of reference significance for improving the emulsifying properties of casein, enhancing the physical stability of oil-in-water emulsions stabilized with casein-soluble soybean polysaccharide complex, and applying casein and sugars.

Key words: casein; soluble soybean polysaccharide; transglutaminase; Maillard reaction; emulsion physical stability

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