Comparison of fermentation behaviors and properties of raspberry wines by spontaneous and controlled alcoholic fermentations.

Torulaspora delbrueckii is a widely studied non-Saccharomyces yeast, described as having a positive impact on the organoleptic quality of wines, however, little is known about its impact on the production of raspberry wine. In this study, we compared combined use of S. cerevisiae/T. delbrueckii pair, i.e., in sequential inoculation (RT) and co-fermentation (RC) modes, with spontaneous fermentation (RU) and single S. cerevisiae inoculation (RS), on various properties of raspberry wine including fermentation behaviors (using yeast counts and next-generation sequencing method), basic composition (by OIV, 2019), volatile profile (using headspace-gas chromatography-ion mobility spectrometry), sensory property (by quantitative descriptive analyses) and biogenic amine levels. All the alcoholic fermentations were completed within 9 days; T. delbrueckii was inhibited by S. cerevisiae in the co-culture; and Saccharomyces and Mrakia were the most abundant species in RU. A total of 40 aromas was identified, with RT abundant in volatile esters, ketones and terpenes and others showing relatively lower intensities. During sensory evaluation, RT was characterized by 'fruity' and 'sweet' notes; RC was notable for a high 'floral' attribute; RU scored the highest in 'pungent' and RS showed intermedium intensities for most descriptors. Partial least squares regression showed the relationship between aromas and sensory descriptors. As for biogenic amine, RU contained the highest total amount and RS had the least. Overall, RT had greater potential to be used in the production of raspberry wine.