Abstract:

The production of purple sweet potato vinegar was explored based on alcohol fermentation by inocluation of
mixed pure cultures of Saccharomyces cerevisiae and Lactobacillus acidophilus. One-factor-at-a-time experiments and
orthogonal array design were employed to optimize inoculum sizes of both starter cultures, inoculation time, volume ratio
between saccharified solutions of purple sweet potato and rice, fermentation temperature and fermentation time on the
contents of alcohol and total acid in fermentation broth. The optimal alcohol fermentation conditions for producing purple
sweet potato vinegar were establsihed as follows: 0.3% Saccharomyces cerevisiae and 10% Lactobacillus acidophilus
cultures were simultaneously inoculated to mixed saccharified solutions of purple sweet potato and rice at a ratio of 5:5 and
then fermented at 30 ℃ for 84 h. The contents of alcohol and total acid of fermentation broth obtained under the optimized
conditions were 7.15% and 0.63 g/100 g, respectively. In conclusion, total acid content in fermentation broth can be
increased by inoculation of Lactobacillus acidophilus, resulting in improved quality of purple sweet potato vinegar.

Key words: purple sweet potato vinegar, alcohol fermentation, lactic bacteria, liquid fermentation