Abstract
The organic volatile flavor compounds in fermented stinky tofu (FST) were studied using SPME-GC/MS. A total of 39 volatile compounds were identified, including nine esters, seven alcohols, five alkenes, four sulfides, three heterocycles, three carboxylic acids, three ketones, two aldehydes, one phenol, one amine and one ether. These compounds were determined by MS, and conformed by comparison of the retention times of the separated constituents with those of authentic samples and by comparison of retention indexes (RIs) of separated constituents with the RIs reported in the literature. The predominant volatile compound in FST was indole, followed by dimethyl trisulfide, phenol, dimethyl disulfide and dimethyl tetrasulfide. In order to find a better extraction time, the extraction times was optimized for each type of SPME fiber; the results show that the best extraction time for Carboxen/PDMS is 60 min, for PDMS/DVB 30 min, for DVB/CAR/PDMS 60 min and for PDMS 75 min. Of the four fibers used in this work, Carboxen/PDMS is found to be the most suitable to extract the organic volatile flavor compounds in fermented stinky tofu.
Highlights
Stinky tofu, called chao tofu, chaw tofu or gray sufu, is one of the traditional Chinese soybean foods
In order to find better extraction time for the four solid-phase microextraction (SPME) fibers, the organic volatile flavor compounds in fermented stinky tofu (FST) 1 were extracted for five different time periods (15, 30, 45, 60 and 75 min, respectively) at 50 °C
The results show that 60 min is more suitable for Carboxen/PDMS among the five chosen extraction time periods
Summary
Called chao tofu, chaw tofu or gray sufu, is one of the traditional Chinese soybean foods. Like some varieties of cheese, stinky tofu has an unpleasant smell, but it tastes delicious, so stinky tofu is called Chinese cheese. According to the process technology, there are two kinds of stinky tofu: unfermented stinky tofu (UST) and fermented stinky tofu (FST) [1]. FST is usually gray, so it is called gray sufu. UST is made by soaking tofu cubes in special stinky brines for 4–6 h. The tofu cubes aren’t fermented before soaking. UST is very popular and often homemade in southern China. It is usually cooked and consumed as snack by deep-fat frying
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