Assessing the Impact of Simultaneous Co-Fermentation on Malolactic Bioconversion and the Quality of Cider Made with Low-Acidity Apples

Abstract

This study investigated the synergistic effects of combining Saccharomyces cerevisiae and Oenococcus oeni during the alcoholic fermentation of a low-acidity cider. The initial population of indigenous wild lactic acid bacteria (LAB) in the apple must was 104 CFU/mL. Alcoholic fermentations were carried out without (Cider I) and with (Cider II) the O. oeni inoculation at 105 CFU/mL. As S. cerevisiae grows, a declining trend was observed in indigenous and inoculated LAB populations. While the wild LAB exhibited higher sensitivity than O. oeni, they were not eliminated during alcoholic fermentation. The addition of O. oeni impacted the growth and metabolic activity of S. cerevisiae. The bioconversion of malic acid into lactic acid predominantly occurred during the growth phase (43–66%) and stationary phase (4–27%). The resurgence of O. oeni following alcoholic fermentation significantly impacted the production of volatile compounds. After 20 days of fermentation, Cider II displayed a twofold increase in these compounds, resulting in a more favorable sensory profile according to evaluators. Consequently, malolactic fermentation (MLF) coincided with alcoholic fermentation, leading to a reduction in malic acid content. Furthermore, post alcoholic fermentation, MLF positively enhanced the aromatic quality of low-acid cider made from apples with low acidity.