Isolation and Identification of Yeast from Acidic Tofu Whey and its Application to Soy Yogurt
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Abstract:
The yeast strain Y isolated from acidic tofu whey was identified as Pichia amenthionina Y by morphological examination, 26S ribosomal DNA sequence analysis, and by means of the Biolog microbial identification system. Further analyses indicated that this strain can grow in a wide temperature range (26 ℃~42 ℃), and that its optimal temperature is 36 ℃. Strain Y and lactic acid bacteria XPL-1 were used as combined starter culture to prepare soy yogurt,, and headspace solid phase microextraction with gas chromatography and tandem mass spectrometry (SPME-GC-MS) was employed to analyze the volatile components in the soy yogurt samples. The data were normalized and then analyzed by principal component analysis (PCA). The results indicated that the characteristic beany flavor of the soy yogurt generally disappeared, and abundant alcohol and ester aroma components were generated, including ethyl acetate, octyl acetate, isoamyl acetate, phenylethanol, and 2,3-butanediol. A higher concentration of ethyl acetate was found in the soy yogurt after fermentation at 36 ℃, in the presence of 2-ethyl hexanol and other aroma components, indicating that P. amenthionina Y is a thermophilic yeast that can produce aroma and remove the beany flavor, and has good prospects for development and practical applications.
