| Summary: | 碩士 === 高苑科技大學 === 化妝品應用系碩士班 === 107 === This study was to investigate the fermentation of Astragalus membranaceusaqueous extract with yeast. Yeast is a wild yeast strain derived from autologous fermentation of pineapple. First, the yeast is activated, cultured, and identified. The yeast was cultured in YPD (Yeast Extract Peptone Dextrose) liquid medium at a constant temperature of 30 °C for 22 hours, and the pH value dropped to about 5.49.Compared with other solid-liquid ratios, this yeast has the best growth condition at a ratio of 1:40 (Astragalus membranaceus: deionized water, W:V).The optimal formula design and verification were done by using the central composite design (COD) and experimental designsoftware (Design Expert). A series of different amount combinations of sucrose (carbon source), skim milk (nitrogen source), and bacterial amount (yeast) were designed. In experiments, it was found that the less nitrogen source, the better the growth of this yeast in the aqueous extract of Astragalus membranaceus. Therefore, the influencing factor of nitrogen source is deleted.Fermentation was carried out by two factors (carbon source and bacterial amount) and 1:40 aqueous extract of Astragalus membranaceus to observe the bacteria growth.We found that the optimal growth of yeast was obtained at 60 hr by adding 20% sucrose and 1.2% bacteriaamount to the 1:40 Astragalus aqueous extract.Fermentation was carried out for 72 hours with 20% sucrose and 1.2% bacterial amount. During the fermentation period, the total polyphenol content was found to be between 145.24 and 192.86 mg Gallic acid / mL; the total sugar content was between 25.33 and 40.15 mg glucose / mL; the DPPH free radical scavenging power was between 2.58 and 4.89 mg Gallic acid / mL ; and the protein degrading enzyme activity was between 19.7 and 29.5 unit / mL.The sensory evaluation of appearance, color, flavor, acidity, sensation, overall sense and total acceptance have high acceptance, indicating that the fermentation broth of Astragalus membranaceusaqueousextract and yeast has potential to become a nutrition drink of health-care on the market in the future.
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