Impact of Co-Inoculation Patterns of Wickerhamomyces anomalus and Saccharomyces cerevisiae on Cider Quality and Aromatic Profiles

Co-inoculation with <i>Saccharomyces cerevisiae</i> and non-<i>Saccharomyces</i> yeasts is an effective method to improve the flavor of cider. <i>Wickerhamomyces anomalus</i>, known for its high ester production capacity, was evaluated in combination with <i>S. cerevisiae</i> to identify optimal mixed yeast inoculants for improved sensory characteristics. Three <i>W. anomalus</i> strains and three inoculation ratio attributes (1:5, 1:1, and 5:1) were tested to assess their impact on the physicochemical indices and sensory attributes of cider. All the strains used as starters developed fermentation-producing ciders with alcoholic degrees between 6.22 and 6.36 (% <i>v</i>/<i>v</i>). Co-inoculation with <i>W. anomalus</i> resulted in significantly higher ester, volatile acid, and higher alcohol levels compared to those of <i>S. cerevisiae</i> monocultures, increasing the complexity of fruity and floral aromas. Furthermore, the proportion of <i>W. anomalus</i> strains in the inoculations was positively correlated with increased aromatic esters and higher alcohols. The Sc-Wa (1:5) cider showed the highest contents of ethyl ethanoate and 3-methylbutan-1-ol, contributing to a nail polish-like aroma. Sc-Wa (1:1) yielded a higher aromatic diversity than did Sc-Wa (5:1), suggesting that co-inoculation with a ratio of 1:1 may provide an effective fermentation strategy for cider aroma enhancement. These findings offer valuable insights into how non-<i>Saccharomyces</i> yeasts can be effectively applied in cider co-fermentation, providing a foundation for their future use in industrial applications.