title: Optimization of the enzymatic deamidation of soy protein by protein-glutaminase and its effect on the functional properties of the protein.
abstract: The effects of enzymatic deamidation by protein-glutaminase (PG) on the functional properties of soy protein isolate (SPI) were studied. Conditions for the deamidation were evaluated by means of response surface methodology (RSM). Optimal conditions based on achieving a high degree of deamidation (DD) with a concurrently low degree of hydrolysis (DH) were 44 °C, enzyme:substrate ratio (E/S) of 40 U/g protein and pH 7.0. Under optimal conditions, both DD and DH increased over time. SDS-PAGE results indicated that lower molecular mass subunits were produced with increasing DD. Far-UV circular dichroism spectra revealed that the α-helix structure decreased with higher DD, while the β-sheet structure increased until 15 min of deamidation (32.9% DD), but then decreased at higher DD. The solubility of deamidated SPI was enhanced under both acidic and neutral conditions. SPI with higher DD showed better emulsifying properties and greater foaming capacity than SPI, while foaming stability was decreased. It is possible to modify and potentially improve the functional properties of SPI by enzymatic deamidation using PG.
authors.affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 1302 West Pennsylvania Avenue, Urbana, Illinois 61801, United States.
authors.forename: Inthawoot
authors.initials: I
authors.lastname: Suppavorasatit
authors.forename: Elvira Gonzalez
authors.initials: EG
authors.lastname: De Mejia
authors.forename: Keith R
authors.initials: KR
authors.lastname: Cadwallader
mesh_terms: D055598:Chemical Phenomena; D005972:Glutaminase / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D017433:Protein Structure, Secondary; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry*
chemical_list: D030262:Soybean Proteins; D005972:Glutaminase