The influence of traditional stir-frying with oil on acceptability, antioxidant activities, nutrients, and the phytic acid content of fermented soybean (tempeh)

Abstract

Purpose

The purpose of this paper was to investigate the acceptability of processed tempeh and the effect of stir-frying on uncooked tempeh composition, total phenolic content (TPC), antioxidant (AO) activities and the phytic acid (PA) concentration.

Design/methodology/approach

Fermentation was performed in the solid-state using soybean (Glycine max) inoculated with Rhizopus oligosporus. The acceptability of tempeh was evaluated by administering a questionnaire. The TPC of uncooked and stir-fried tempeh was examined using Folin-Ciocalteu’s method, and PA was analyzed by high-performance liquid chromatography. AO activities were measured by the thiobarbituric acid reactive substance (TBARS) and ferric ion reducing/antioxidant power methods. The stir-fried tempeh was more acceptable than other preparations to the panelists.

Findings

In comparison with the uncooked tempeh, stir-fried tempeh showed higher fat composition, in addition to decreased levels of minerals, PA and TBARS.

Originality/value

Soy foods are an important source of protein. However, conventional cooking methods could change the chemical properties in soy foods. To avoid additional oil that adds calories, consumers might opt for other cooking methods, such as steaming.

Citation

Setiawan, B., Thamtam, S.K., Jati, I.R.A., Purwestri, R.C., Nohr, D. and Biesalski, H.K. (2016), "The influence of traditional stir-frying with oil on acceptability, antioxidant activities, nutrients, and the phytic acid content of fermented soybean (tempeh)", Nutrition & Food Science, Vol. 46 No. 2, pp. 259-271. https://doi.org/10.1108/NFS-09-2015-0105