Volatile composition of bilberry wines fermented with non-Saccharomyces and Saccharomyces yeasts in pure, sequential and simultaneous inoculations.

Bilberry (Vaccinium myrtillus L.) juice was fermented with Torulaspora delbrueckii (TD291 and TD70526) and Schizosaccharomyces pombe (SP3796 and SP70572) in pure fermentation as well as in sequential and simultaneous inoculations with Saccharomyces cerevisiae 1116 (SC1116). Altogether, 56 volatile compounds were identified and semi-quantified with HS-SPME-GC/MS in bilberry products. Yeast fermentation prominently enhanced the aroma complexity of bilberry with a sharp increase in alcohols, esters, aldehydes, and acetals. Compared to S. cerevisiae, T. delbrueckii produced less ethanol but more fusel alcohols that potentially enhance "alcohol" and "nail polish" odors in TD70526 and less "fruity" esters in TD291. SP70572 resulted in high productions of undesirable compounds of acetoin and acetaldehyde but a low content of higher alcohols and esters, SP3796 produced a high content of fatty acid ethyl esters and acetoin. In comparison with monoculture of non-Saccharomyces yeast, sequential and simultaneous cultures of S. pombe and S. cerevisiae significantly decreased the content of acetoin while increased the relative level of esters; sequential cultures of T. delbrueckii and S. cerevisiae remarkably increased the concentration of acetaldehyde; simultaneous inoculations of S. cerevisiae with TD70526 and TD291 significantly decreased the content of fusel alcohols and increased the content of esters, respectively. The findings suggested that non-Saccharomyces yeasts possess the potential to affect and modulate the aromatic profile of fermented bilberry products. Sequential and simultaneous inoculations with S. pombe strains and S. cerevisiae as well as simultaneous fermentation using T. delbrueckii strains and S. cerevisiae are optimal strategies to positively influence the aroma profile of bilberry wines.