11-6 |
Pectinase and proteases: Effects on protein and functional properties of soy protein ingredients |
S. JUNG1, P. A. Murphy1, and L. A. Johnson2. (1) Dept. of Food Science & Human Nutrition, Iowa State Univ., 2312 Food Sciences Bldg., Ames, IA 50011, (2) Center for Crops Utilization Research, Iowa State Univ., Dept. of Food Science & Human Nutrition, 1041 Food Sciences Bldg., Ames, IA 50011 Soy protein ingredient production can be improved using several approaches. First, the protein extractability yield on a production scale is about 50%, which results in a considerable economic loss. Additionally, soy products could be modified in order to increase their functional properties. One approach to improve these parameters is through enzyme modification. The objectives of this work were: 1. to increase the protein extractability from defatted soy flakes using pectinase; 2. to determine the functional properties of the protein isolate obtained with the use of this enzyme; 3. to compare the functional properties of Extruded-Expelled (E-E) flour and soy concentrate after hydrolysis with proteases at a low degree of hydrolysis (DH<10%). The protein content was determined by Dumas and Biuret methods. The protein characteristics were followed by SDS-PAGE electrophoresis and differential scanning calorimetry (DSC). Functional properties included solubility profile (pH 3.5-8), hydrophobicity, emulsification capacity, activity and stability, and foaming capacity and stability. The pH stat method was used to determine the degree of hydrolysis. The slurry obtained after enzyme modifications was freeze-dried before analysis. Multifect Pectinase at a concentration of 5 and 10% (enzyme weight / protein weight) led to an increase of around 50% of protein extractability compared to the control. The protein isolate obtained with this pectinase showed interesting functional properties, with modifications of the emulsification activity and foaming activity and stability. In addition to changes in the protein functionality, modifications of the enthalpy of denaturation and the SDS-PAGE profiles of the protein isolate were observed. The glycinin (11S) was not altered by the treatment, however, b-conglycinin (7S) was modified by deglycosylation. The extent of modification of the 7S was dependant of the enzyme concentration. Additionally, hydrolysates from soy E-E flour and soy concentrate, obtained at a DH of 4 and 6%, were characterized by their functional properties.
Session 11, Food Chemistry: Proteins I
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