NMR-based metabolic profiling of different yeast fermented apple juices

NMR based metabolic profiling was used to investigate metabolic changes in ciders fermented by yeast species as valuable tool for the identification of metabolites responsible for yeast activities. 1H NMR spectra of apple ciders produced by Saccharomyces cerevisiae EC1118, Torulaspora delbrueckii TD291, Starmerella bacillaris YR21, Hanseniaspora osmophila HO16, Hanseniaspora uvarum Y4M, and Saccharomyces uvarum SU3, revealed to be dominated by glycerol and organic acids signals. The aromatic region showed the presence of low intense signals referred to epicatechin, catechin, chlorogenate, xanthine, uracil, tyrosol, fumarate, histamine, and histidine. The anomeric region showed signals related to xylose, arabinose, glucose, fructose and sucrose. Finally, in the aliphatic region, signals due to amino acids like alanine, aspartate, asparagine, isoleucine and threonine, organic acids like acetate, lactate, malate, pyruvate, quinate, succinate, and alcohols like 2,3 butanediol, ethanol, and glycerol and sterol were detected. Principal component analysis performed considering NMR data from either all spectral regions and only aromatic region revealed the potentiality to discriminate the yeast action. Signals due to glucose, fructose, glycerol, malate, fumarate, tyrosol, histidine, and histamine resulted discriminant for sample differentiation. This study, the first one by NMR, provides preliminary insights on the metabolic differences among yeast species involved in cider production.