Contents and bioconversion of β-glycoside isoflavones to aglycones in the processing conditions of soybean tempeh

Cristiane Wing Chong Borges,Josemeyre Bonifácio Da Silva,Elza Iouko Ida,José Marcos Gontijo Mandarino,Silvia Benedetti,Mercedes Concórdia Carrão-Panizzi

doi:10.1590/s0100-204x2016000300009

Cristiane Wing Chong Borges, Josemeyre Bonifácio Da Silva + Show 4 more

Open Access

https://doi.org/10.1590/s0100-204x2016000300009

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Abstract

Abstract: The objective of this work was to evaluate the effect of the processing conditions of soybean tempeh on the contents of β-glycoside isoflavones and on their bioconversion into aglycones. Different times of soaking (6, 12, and 18 hours), cooking (15, 30, and 45 minutes), and fermentation (18, 24, and 30 hours) with Rhizopus oligosporus at 37°C were evaluated for tempeh preparation. Grains from the cultivar 'BRS 267' were used, and the experiment was carried out according to a central composite design (23). The response functions comprised the contents of genistin, malonyldaidzin, malonylgenistin, daidzein, and genistein, quantified by ultraperformance liquid chromatography (UPLC). Soaking, cooking, and fermentation times change the content, profile, and distribution of the different forms of isoflavones in tempeh. The highest bioconversion of glycoside isoflavones into aglycones occurred in 6-hour soaked soybean grains, whose cotyledons were cooked for 15 minutes and subjected to 18-hour fermentation.

Highlights

Tempeh is a traditional Indonesian food of high nutritional quality, obtained by fungal fermentation of dehulled, soaked, and cooked soybean grains (Starzyǹska‐Janiszewska et al, 2014)
The tempeh is obtained by fermentation of soybean grains with Rhizopus oligosporus, and it is an excellent protein source that has all the essential amino acids for human nutrition, in addition to dietary fibers, calcium, vitamin B12, folic acid, low sodium content, and unsaturated fats (United States Department of Agriculture, 2008)
Soybean grains are soaked in water for 10 to 12 hours, at room temperature, in order to facilitate the removal of the hulls

Summary

Introduction

Tempeh is a traditional Indonesian food of high nutritional quality, obtained by fungal fermentation of dehulled, soaked, and cooked soybean grains (Starzyǹska‐Janiszewska et al, 2014). It is commercially available in different forms, such as fried, boiled, steamed or roasted. The tempeh is obtained by fermentation of soybean grains with Rhizopus oligosporus, and it is an excellent protein source that has all the essential amino acids for human nutrition, in addition to dietary fibers, calcium, vitamin B12, folic acid, low sodium content, and unsaturated fats (United States Department of Agriculture, 2008). The preparation process of soy tempeh includes soaking soybean grains, cooking their cotyledons and fermentating them by the inoculation with Rhizopus. Rhizopus oligosporus is the most often used fungus for fermentation of soybean tempeh, due to its rapid growth between 30 and 42°C (Shurtleff & Aoyagi, 2001)

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