Author
 |
Sessa, David |
|
Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/3/2003 Publication Date: 10/15/2003 Citation: Sessa, D.J. Processing of soybean hulls to enhance the distribution and extraction of value-added proteins*. Journal of the Science of Food and Agriculture 84.2003. p. 75-82. Interpretive Summary: Soybean hulls, with an annual production of over 3 million metric tons and a cost of three cents per pound, are a source of two valuable proteins: peroxidase (SBP) and a Bowman-Birk type protease inhibitor (BBI). Industrially, SBP is used as oxidant in European bread-baking and can be used as a replacement for formaldehyde in cross-linking phenols for adhesive production. BBI is a potent anticarcinogen and chemopreventive agent. Because these proteins are minor constituents of hulls, air classification was used to distribute and enrich them in fractions amenable for their concentration and purification. Processing including aqueous extractions of air-classified fractions, column chromatography to concentrate BBI, ultrafiltration/diafiltration to concentrate SBP were used. Selective fractions from air-classification of hulls can be processed to concentrate these value-added proteins. Information should be useful to scientists in industry and academia interested in finding new and expanded uses for soy hulls. Technical Abstract: Soybean hulls contain peroxidase (SBP) and Bowman-Birk type protease inhibitor (BBI). SBP is used in the European bread-baking industry and BBI isolated from dehulled, defatted soy flour possesses cancer preventive and anticarcinogenic properties. Because hulls possess a low percentage of nitrogen where fiber and other carbohydrates are the major components our objective was to determine whether air classification of milled hulls could be used to fractionate and enrich these value-added proteins. Hulls were pin-milled three times at 18000 rpm, followed by air classification to yield fractions with particle size distributions ranging from <15 micrometers (um) to >30 um. The finely ground fractions with particle sizes ranging from <15 to 18 um were enriched with nitrogen and lipid when compared with the coarser ground fractions. Yields of extractable nitrogenous components from aqueous extracts were quantified at a variety of pHs, homogenization speeds and times. BBI and SBP were confirmed by polyacrylamide gel electrophoresis with known standards. Based on assays for SBP and BBI activities, BBI was concentrated in the fines fractions, whereas, SBP resided mainly in the coarest fraction. Dry milling and air classification of soybean hulls can be used to distribute the BBI and SBP into two product streams to facilitate their isolation and purification. |
