Effects of mixed fermentation of different lactic acid bacteria and yeast on phytic acid degradation and flavor compounds in sourdough

Sourdough plays an important role in improving product quality. In this study, single-strain and mixed fermentation of Lactobacillus paracasei LG0260, Lactobacillus plantarum LG1034, Lactococcus lactis LG0827, Saccharomyces cerevisiae J2815 and Saccharomyces cerevisiae J8202 were used to prepare type II sourdough, which was used to evaluate the ability of mixed fermentation to improve the quality of sourdough and increase volatile flavor compounds. In sourdough, mixed fermentation reduced the number of lactic acid bacteria (LAB) and yeasts colonies, accompanied by a decrease in acidity. However, the organic acid analysis found that mixed fermentation increased the content of acetic acid and reduced the content of lactic acid. Mixed fermentation enhanced the degradation of phytic acid. It was found that sourdough MY1L3 degrades up to 96.6% of phytic acid. In addition, the total polyphenol content of mixed fermentation was decreased, but the DPPH free radical scavenging ability was enhanced. It was found by HS-SPME-GC-MS that mixed-fermented sourdough had more complex flavor compounds, such as acids, aldehydes, and esters. The differences in the metabolic properties of different starter cultures in sourdough will provide a theoretical reference for the improvement of sourdough quality.