Evaluation of three methods for the extraction of proteins from soybean curd residue (okara)

GOMEZ AG; AMBROSI V; POLENTA GA; GUIDI SM

Ciudad Autónoma de Buenos Aires

Conferencia; VII INTERNATIONAL CONFERENCE ON PROTEINS AND FOOD COLLOIDS CIPCA VII; 2017

Dra. Ana M.R. Pilosof (Departamento de Industrias/ITAPROQ-Conicet, FCEN, UBA), con la colaboración del grupo dirigido por la Dra. María Cristina Añón del CIDCA-CONICET-UNLP.

The development of foods enriched with high-nutritional-quality proteins is strategic to properly accompany the exponential growth of the older population, associated to the significant increase in the life-expectancy. This would help prevent the development of degenerative muscle losses associated to age, generally known as sarcopenia. Therefore, the exploration of new protein sources beyond the classical ones will be a key factor for the innovative development of protein ingredients for such purposes. There is a clear tendency nowadays towards the use of plant origin proteins in replacement of animal proteins, mainly because of economical and health reasons. Among these, soybean-base products are playing an increasingly important role in the food industry, because of the higher nutritional quality and better digestibility of their proteins in comparison to other proteins of plant origin. Okara is a by-product obtained during the processing of soybean for soy milk and tofu. The high amounts of okara generated by the food industry, together with its underutilization, constitute in some Countries a serious environmental problem. The functional and nutritional properties of okara are comparable to those of soy isolates, with the ratio of essential total amino acids being similar to those of soy milk and tofu. Although okara can be considered as a promising alternative source of protein, its low solubility prevents from the generalized use of this product. Considering that in Argentina, okara is mainly used as an animal food, the objective of the present study was to nutritionally characterize the okara obtained from the production of a popular soy milk in Argentina, and to compare the protein recovery yield of three different extraction methods: solubilisation in basic medium and precipitation by pH change (A), solubilisation in basic medium and concentration by ultrafiltration (3 kDa cutoff membrane) (B), and solubilisation in buffered phenol and precipitation in ammonium acetate methanolic solution (C). Okara samples obtained from the industry were transported to the lab, conditioned, frozen and stored under vacuum at -20° C until use. Different analyses were performed: total protein content, ash, total lipid content, humidity, and protein profile by SDS-PAGE. Expressed in relation to the dry weight, okara had a total protein content of 11,71 ± 0,04 %, 1,84 ± 0,18 % of ash, 13,32 ± 0,14 % of total lipids, and 82,01 ± 0,82 % of humidity. The highest yield was obtained by the method C, which was 50% and 64% higher than A and B methods, respectively, while no difference was found in the protein pattern among the three methods. According to results, phenolic extraction showed the best performance among the method assayed. However, by considering other practical and economical aspects, the solubilisation in basic medium followed by ultrafiltration would present a more feasible alternative.