Application of two extraction methods: SPME and SAFE for identification of volatile compounds and key odorants in tempeh

Abstract

Tempeh is a traditional Indonesian fermented product, made from soy seeds inoculated with mould, Rhizopuz oligosporus. Tempeh is highly nutritious, easily digestible and delicious food, and is especially interesting for consumers looking for products rich in healthy components for their diet. The aim of this study was to estimate the changes in the flavour compounds profile during fermentation and frying of tempeh. For tempeh production bean seeds (Phaseolus vulgaris) were boiled and inoculated by spores of Rhizopus oligosporus. Volatile compounds produced after the fermentation and frying processes, were isolated using SPME and SAFE techniques SPME extraction allowed the monitorization of volatile compounds formed during tempeh fermentation such as pyrazines, ketones, aldehydes, alcohols and sulphuric compounds. It has been noticed that longer fermentation time increased formation of pyrazines, aldehydes, ketones and alcohols but had no influence on sulphuric compounds. On the other hand frying of 5 days fermented tempeh produced an increase of aldehydes and sulphuric compounds. By application of SAFE extraction and GCO analysis, many compounds were identified in tempeh with 24 hours of fermentation, 5 days and in fried tempeh with highest FD for boiled potatoes and popcorn notes. Application of GC×GC/TOFMS analysis allowed for their identification as methional and methyl pyrazine.