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Bioactive Proteins and Energy Value of Okara as a Byproduct in Hydrothermal Processing of Soy Milk

Stanojevic, Sladjana P., Barac, Miroljub B., Pesic, Mirjana B., Jankovic, Vanja S., Vucelic-Radovic, Biljana V.
Journal of agricultural and food chemistry 2013 v.61 no.38 pp. 9210-9219
antinutritional factors, bioactive properties, carbohydrates, cooking, cysteine, energy, functional foods, lectins, lipids, nutritive value, physicochemical properties, proximate composition, soybeans, soymilk, trypsin inhibitors, urease
The nutritional properties of raw okara obtained as a byproduct from six soybean varieties during hydrothermal cooking (HTC) of soy milk were assessed. The composition and residual activity (rTIA) of trypsin inhibitors (TIs), contents of lectin, proteins, fats, and carbohydrates, and energy values (EV) were correlated with the respective physicochemical properties of soybean and okara. Kunitz (KTI) and Bowman–Birk (BBI) TIs both comprised okara rTIA. TIs content was higher in okara (5.19–14.40%) than in soybean (3.10–12.17%), which additionally enriched okara by cysteine. Contents of KTI (r = 1.00;p < 0.05) and BBI (r = 0.89;p < 0.05) as well as BBI monomeric (r = 0.89;p < 0.05) and polymeric forms (r = 0.95;p < 0.05) in okara and in soybean were strongly correlated. Low urease index activity indicated that okara was heated adequately to inactivate antinutritional factors. The proximate composition of raw okara, advantageous rTIA, and a very low EV (2.74–3.78 kJ/g) qualify this byproduct for potential application in food preparation as a functional ingredient in dietary products.