Aspectos quÃmico, fÃsico-quÃmico e sensorial de extratos de soja e tofus obtidos dos cultivares de soja convencional e livre de lipoxigenase / Technological, physicochemical, biochemical and sensorial studies of soybean extracts and respective tofus obtained from conventional and lipoxygenase-free soybean cultivars. / Technological, physicochemical, biochemical and sensorial studies of soybean extracts and respective tofus obtained from conventional and lipoxygenase-free soybean cultivars. / Aspectos quÃmico, fÃsico-quÃmico e sensorial de extratos de soja e tofus obtidos dos cultivares de soja convencional e livre de lipoxigenase

Sueli Ciabotti

The work was conducted in the laboratories of the Food Science Department of the Federal University of Lavras âMG. Soybean grains [Glycine max (l) Merrill] utilized were: conventional cultivar BRS 133 and cultivar BRS 213, genetically improved and suitable for human consumption, lipoxygenase-free, granted by Embrapa-Soja PR. For reasons proved, soybean consumption has increased in the western countries, but, with a factor limiting by the population, which is the flavor of its products which are ascribed to the action of lipoxigenase enzyme in soybean grains by the hydroperoxidation of polyunsaturated fatty acids and by the interaction of the hydrolysis products with proteins. The objective of this work was to evaluate under the technological, chemical, physicochemical, biochemical and sensorial soymilk and respective tofus obtained from soybean cultivars: conventional with and without the use of bleaching in their early processing steps and the lipoxygenase-free cultivar. The manufacture process by the use of the bleaching of conventional soybean grains presented unfavorable values as to losses of soaking water-soluble solids and total solids in the soybean extract and further, it presented a low yield of tofu and the texture measured by the texturometer was markedly affected. In the sensorial analyses, the heat processing to which conventional soybean was submitted proved indispensable to make the âflavorâ of the soybean extract more agreeable to the panelistsâ taste not interfering either in their appearance or in their color, having always as a reference, lipoxygenase free soybean, but, bleaching, in turn, depreciated not only âflavorâ but also âtextureâ and âappearanceâ of the respective tofus. The composition of macronutrients was similar in both soybean cultivars studied. Alterations in the chemical composition of the soymilk and of the tofus were ascribed to bleaching (98 oC/5â) and grain hydration to which conventional soybean was submitted, where substances were leached into the soaking water of the grains. The bleaching step of conventional soybean grains enabled greater The heat treatment (bleaching) to which the grain was submitted for making of the soymilk was effective in reducing retention of isoflavones in tofu (68%) and the tofu which less retained isoflavones was the one obtained from lipoxygenase-free soybean (44%). lipoxygenase activity as compared with the soybean free of this enzyme enough to eliminate the activity of the trypsin inhibitors in 79% of the conventional soybean tofu, 81% in the bleached soybean tofu and 82% in the lipoxygenase free soybean tofus.

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