| Summary: | 碩士 === 大同大學 === 生物工程研究所 === 92 === Abstract
In this study, rice vinegars and red yeast rice vinegars were prepared. The biochemical changes of rice vinegars and red yeast rice vinegars during koji-making, alcohol fermentation, acetic acid fermentation and aging periods were under investigation. Meanwhile, aromatic volatiles of rice vinegars and red yeast rice vinegars were also identified and quantified. The results revealed that red yeast rice could be obtained after culturing Monascus ruber BCRC31535 on rice for 10 d. The content of monacolin k increased to 45.3 mg/kg dry wt. Addition of red yeast rice to rice koji decreased the α-amylase activity of rice koji. During alcohol fermentation of rice moromi and red yeast rice moromi, the amount of reducing sugar decreased and the amount of alcohol increased with increasing time. The concentration of ethanol in rice moromi and red yeast rice moromi increased to 10% after 5 d of alcohol fermentation. The content of red pigment in red yeast rice moromi also increased. However, the content of red pigment content in rice moromi was much lower. The concentration of monacolin k in red yeast rice moromi was below detection limit. During acetic acid fermentation of rice wine by Acetobacter aceti BCRC 12325, the concentration of ethanol decreased and acetic acid formed. The final concentration of acetic acid of rice vinegar and red yeast rice vinegar was 4.7% and the content of red pigment in red yeast rice vinegar slightly decreased at the end of fermentation. The aroma compounds identified in rice vinegar and red yeast rice vinegar were similar. Twenty-four compounds, including 7 alcohols, 7 esters, 6 acids, 2 aldehydes and 2 ketones, were identified. The amount of 2,3-butanediol was highest in rice vinegar and red yeast rice vinegar, followed by 2-phenylethanol. After acetic acid fermentation for 48h, the amount of 2,3-butanediol significantly increased. However, the amounts of most of the aroma compounds decreased after aging for 2 months.
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