Abstract:

The two-step fermentation process of Saccharomyces cerevisiae and lactic acid bacteria was studied to prepare passionfruit pericarp pulp with high viability of lactic acid bacteria and Saccharomyces cerevisiae, good retention of polyphenols and mellow flavor. Through single factor and orthogonal experiments, the fermentation process parameters of single lactic acid bacteria and yeast were optimized by taking the number of live S. cerevisiae and lactic acid bacteria, total phenol and ethanol production as the indexes. On this basis, by measuring the changes of total acid content, viable bacteria number and total phenol content, the technological parameters of the two-step fermentation of passionflower pericarp pulp were determined. The total fermentation time was 40 h. The initial inoculation amount of the mother bacteria was 1.5%. After 16 h of fermentation at 29 ℃, 2.0% mixed Lactobacillus (L. casei∶L. plantarum = 1∶1) was added, and the fermentation continued at 37 ℃ for 24 h. In the fermentation broth, the number of live Lactobacillus was 8.9 lg CFU/mL, the number of live S. cerevisiae was 7.78 lg CFU/mL, the total phenol content was 24.0 μg/mL, and the total acid content was 4.4 mg/mL. The two-step fermentation method had the advantages of S. cerevisiae producing aroma, ethanol inhibiting impurities, and lactic acid bacteria improving acidity and retaining polyphenols.

Key words: passionfruit, Saccharomyces cerevisiae, lactic acid bacteria, two-step fermentation