Influence of 4 lactic acid bacteria on the flavor profile of fermented apple juice

The objective of this study was to evaluate the influence of 4 lactic acid bacteria (LAB), Lactobacillus acidophilus, L. rhamnosus, L. casei and L. plantarum, on the flavor profile of fermented apple juice. The changes in bacterial populations, concentrations of organic acids and overall volatile aroma compounds were monitored during fermentation (0–80 h) and after 1, 7, 14, 21 and 28 days of refrigerated storage. All 4 strains exhibited a good capacity for growth in the apple juice. L. casei and L. rhamnosus produced larger concentrations of total acids and showed higher microbial viability than the other strains. The formation of lactic acid at the expense of malic acid was a common feature of the fermented samples, and this trend was most evident in the samples containing L. acidophilus . The aromatic profiles of the fermented juices were characterized by the presence of 53 volatile compounds. By using an electronic nose, we were able to discriminate among the different samples during refrigerated storage. While most of the volatile compounds associated with the typical aroma of apple juice were retained or enriched after fermentation and storage, some new compounds like acetaldehydes and ketones were generated from the fermentation by LAB. L. acidophilus affected the volatile profiles of the fermented juice more than the other strains. It significantly increased the important aromatic components: 2-ethylhexanol, 3-methyl-1-butanol, 2-methyl-1-butanol and ethyl acetate.