14B-11 |
Production of soy protein concentrate by ultrafiltration |
N. S. Krishna Kumar, M. K. Yea, and M. CHERYAN. Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 109 Agricultural Bioprocess Lab., 1302 W. Pennsylvania Ave., Urbana, IL 61801 The growing demand for soy products has created interest for new and improved methods of producing soy protein concentrates and isolates. Traditional processing techniques sometimes result in products with poor functional properties and generates a whey-like waste stream containing proteins and other components. To overcome these problems and produce superior products, we are using membrane technology for the manufacture of soy products. The appropriate membrane and operating parameters can selectively remove undesirable components resulting in purified protein isolates or concentrates with better functional properties since the microenvironment is not being altered during ultrafiltration (UF). The objective of this work was to optimize membrane processing parameters to maximize yield and minimize cost of producing soy protein concentrates. Defatted soy flour was suspended in water and processed at 50°C with a commercial 4" spiral wound ultrafiltration module. The independent variables were feed concentration, pressure, cross-flow rate and concentration factor. The measured variables were flux, rejection of protein and other components, and yield of product. With soy flour suspensions of 2% total solids (TS), the flux at a transmembrane pressure of 35 psi (240 kPa) and pressure drop of 10 psi (69 kPa) was 73 liters per square meter per hour (LMH). Flux decreased significantly at higher retentate solids concentrations. Typical asymptotic flux behavior was observed when transmembrane pressure was increased due to concentration polarization effects. Protein content was increased from 50% (dry basis) in the flour to 65-70% by ultrafiltration and/or diafiltration. There are several benefits of using membranes for producing soy products, among them: the mild processing conditions, the chemical-free production process and the retention of soy whey proteins in the UF product. This should result in better functional properties as well as higher yield of product compared to traditional methods.
Session 14B, Food Chemistry: Physicochemical properties
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