Abstract
Abstract Characteristics of water-soluble flours from soy (SF), soy tempe (STF), and germinated-soy tempe (GTF) were compared with those of commercial soy protein isolate (SPI). Defatted flour of soy, soy tempe, and germinated soy tempe were extracted in alkaline water (pH 9) and freeze dried to produce water-soluble flours. Protein contents of SF, STF, and GTF were 49%, 47%, and 51%, respectively, and lower than that of SPI (84%). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles showed that STF and GTF contained lower molecular size of proteins compared to SF and SPI. Trypsin inhibitor activity was detected only in SPI. The most abundant phytic acid was contained in SF, followed in order of decreasing abundance, by SPI, STF, and GTF. Antiradical activities measured by DPPH assay also showed significant variations, and the activity was highest in GTF, followed in order of decreasing activities, by STF, SF, and SPI. The foaming and emulsion capacities of STF and GTF were significantly lower than SPI, but higher than SF. These data strongly suggest that STF and GTF have better functional characteristics than commercial SPI. However, optimization of the extraction process is needed to improve the yield and protein content.
Highlights
Tempe is popular fermented food in Indonesia
There is no significant difference in moisture content among samples
Ash as water-soluble component was solved during extraction which resulted in water-soluble flour with high ash content
Summary
Tempe is popular fermented food in Indonesia. The health benefits of tempe have been reported (Astuti et al, 2000). Zhan & Ho (2005) reported that tempe could significantly reduce total cholesterol, LDL, and triglycerides content in blood. Tempe is known to contain high quality and high digestibility of protein. Mice fed with tempe flour showed significantly higher feed conversion ratio and true protein digestibility than mice fed with soy flour (Astawan et al, 2015). Soybean as the raw material of tempe is rich in essential amino acids compared to other plant protein sources (Soares et al, 2005). The antinutrient compounds of soybean was reduced during tempe processing (Haron & Raob, 2014)
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