title: Functional properties of a cross-linked soy protein-gelatin composite towards limited tryptic digestion of two extents.
abstract: BACKGROUND
  Both enzymatic cross-linking and hydrolysis are used to treat food proteins for functionality modification. The present study aimed to reveal the impact of limited tryptic digestion on some functional properties of a cross-linked composite generated from soy protein isolate and gelatin by transglutaminase.
  
  
  RESULTS
  The composite was digested by trypsin for 1.5 and 4 h to produce two hydrolyzed composites with degrees of hydrolysis of 1% and 2%, respectively. Electrophoretic and chemical analysis showed that only part of the composite was degraded, and the gelatin fraction in the composite was more sensitive to tryptic digestion than the soy protein fraction. The hydrolyzed composites exhibited higher protein dispersion index at pH 4.5 or 7.0 and surface hydrophobicity, better digestibility in vitro, emulsifying property and oil absorption capacity, but lower water holding capacity and rheological properties (apparent viscosity, storage and loss modulus) than the composite. Compared to soy protein isolate, the hydrolyzed composites had better rheological properties, and higher water-holding capacity and emulsion stability index.
  
  
  CONCLUSIONS
  The applied tryptic digestion conferred some improved properties on the hydrolyzed composites compared with the composite or soy protein isolate, and has potential for obtaining a new functional ingredient for processed foods.
authors.affiliation: Key Laboratory of Dairy Science, Ministry of Education, Northeast Agricultural University, 150030, Harbin, People's Republic of China.
authors.forename: Wen-Wen
authors.initials: WW
authors.lastname: Sheng
authors.forename: Xin-Huai
authors.initials: XH
authors.lastname: Zhao
mesh_terms: D004655:Emulsions; D005780:Gelatin / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D014674:Plant Proteins, Dietary / Q000378:metabolism*; D012212:Rheology; D012995:Solubility; D030262:Soybean Proteins / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism*; D014783:Viscosity; D014867:Water
chemical_list: D004655:Emulsions; D014674:Plant Proteins, Dietary; D030262:Soybean Proteins; D014867:Water; D005780:Gelatin; D014357:Trypsin
keywords: functional property; limited hydrolysis; rheological property; soy protein-gelatin composite; trypsin