Effect of Solid-State Fermentation Tempe Type on Antioxidant and Nutritional Parameters of Buckwheat Groats as Compared with Hydrothermal Processing

The effect of fermentation with Rhizopus oligosporus, roasting and cooking on functional parameters and nutritional composition of unroasted buckwheat groats was studied. Tempe showed 57 and 124% higher activity against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS●+) than cooked unroasted and roasted groats, respectively. Efficient doses of mg material necessary to scavenge ●OH (IC50) and exert reducing power (RP0.5) were decreased in tempe (by 61% and about 30%, respectively, as compared with roasted groats). All the parameters were strongly correlated with the soluble phenol level. Tempe contained more thiamine (2.5-fold) and riboflavin (7.5-fold) than cooked buckwheat. It had 143 g/kg protein of the highest Cys + Met and Tyr + Phe levels. In vitro bioavailability of tempe protein (56%) was higher than cooked unroasted groats (41%) and similar to cooked roasted ones. Sensory analysis of buckwheat tempe was concluded with a good overall assessment. Tempe-type fermentation may be recommended as a favorable technique of unroasted buckwheat groats processing. Practical Applications Conventional cooking and/or roasting of buckwheat seeds influences the nutritional composition and partially diminishes the functional parameters of groats. Tempe-type product obtained from unroasted groats is a convenient food of improved parameters that may broaden the gluten-free product spectrum on the market. Fermented buckwheat groats are also a potential source of flour of advantageous antioxidant parameters for application as a food additive.