15 Composition and Functionality of Protein, Starch, and Fiber from Wet and Dry Processing of Grain Legumes 1
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F. W.Sosulski and K. Sosulski 1
Department of Crop Science and Plant Ecology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0 Biomass Resources, Saskatchewan Research Council, Saskatoon, Saskatchewan, Canada S7N 0X1
Downloaded by CORNELL UNIV on September 9, 2016 | http://pubs.acs.org Publication Date: June 18, 1986 | doi: 10.1021/bk-1986-0312.ch015
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The field pea (Pisum sativum) and small fababean (Vicia faba minor) were pin milled and a i r classified into protein and starch fractions or, alternately, the protein, starch and fiber were extracted by an aqueous alkali procedure. The efficiencies of protein (75-80%) and starch (88-93%) recoveries by the dry process were higher than the 73-79% recoveries by wet processing, and there were no losses of solids in the whey and wash water or need for effluent recovery. The starch fraction was similar to refined starch in most functional properties except for a low amylograph viscosity. The protein fraction showed low nitrogen solubility and rather low water hydration and oil absorption values relative to those of the proteinates but oil emulsification was quite high. Refined legume fiber had a water hydration capacity of over 20 g/g product. C h a r a c t e r i s t i c a l l y , legume seeds are r i c h in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal d i e t s . Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water s o l u b i l i t y , water and fat binding and emulsification. Thus soybean f l o u r s , protein concentrates and i s o l a t e s have been used widely as n u t r i t i o n a l supplements and functional ingredients in foods. Most grain legumes are consumed primarily as whole or s p l i t seeds, and only limited quantities are processed into flours or more refined products. Starchy legume flours appeared to have weaker functional properties than defatted soybean or lupine flours (1) , due in part to t h e i r lower protein contents. To overcome the problem of variable protein composition among samples of f i e l d peas and other grain legumes, Youngs (2^) developed a process for separation of the protein and starch fractions in the seeds by fine grinding and a i r c l a s s i f i c a t i o n . The fine f r a c t i o n , obtained in 0097-6156/86/0312-0176506.00/0 © 1986 American Chemical Society
Ory; Plant Proteins: Applications, Biological Effects, and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
Downloaded by CORNELL UNIV on September 9, 2016 | http://pubs.acs.org Publication Date: June 18, 1986 | doi: 10.1021/bk-1986-0312.ch015
15.
SOSULSKI AND SOSULSKI
Protein, Starch, and Fiber from Grain Legumes
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yields of about 25%, contained 48-67% of protein, depending upon the legume species (3). The functional properties of oil absorption, emulsification and whippability in the a i r - c l a s s i f i e d protein fractions were greatly enhanced over the f l o u r s . The oligosaccharides, t r y p s i n i n h i b i t o r s , hemagglutinins, saponins, phytic acid and, in fababean, vicine and convicine concentrated into the fine f r a c t i o n with the protein ( 4 ^ ) . Numerous other investigators have evaluated the fractions obtained by a i r c l a s s i f i c a t i o n of finely-ground flours from f i e l d pea, fababean and other starchy legumes (6,7_,
