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Cider fermentation with three Williopsis saturnus yeast strains and volatile changes

Aung, Ma Thandar, Lee, Pin-Rou, Yu, Bin, Liu, Shao-Quan
Annals of microbiology 2015 v.65 no.2 pp. 921-928
ciders, ethanol, ethyl acetate, fermentation, isoamyl alcohol, odors, pH, volatile compounds, yeasts
Williopsis saturnus var. subsufficiens NCYC 2728, W. saturnus var. saturnus NCYC 22 and W. saturnus var. mrakii NCYC 500 were used to carry out cider fermentation to assess their impact on the volatile composition of cider. The changes of yeast cell population, °Brix and pH were similar among the three yeasts. Strain NCYC 500 grew best, with the highest cell population of 1.14 × 10⁸ CFU ml⁻¹, followed by strains NCYC 2728 and NCYC 22 (8 × 10⁷ CFU ml⁻¹and 3.19 × 10⁷ CFU ml⁻¹respectively). Esters were the most abundant volatiles produced, followed by alcohols. Among the esters, ethyl acetate, 2-phenylethyl acetate, isoamyl acetate, cis-3-hexenyl acetate and hexyl acetate were the major volatiles. The major alcohols were ethanol, isoamyl alcohol, 2-phenylethyl alcohol and isobutyl alcohol. The three Williopsis yeasts transformed volatile compounds during cider fermentation with significant variations in terms of volatile production and degradation. This study implied that fermentation with Williopsis yeasts could result in cider with a more complex yet fruity aroma.