Production of the Sicilian distillate "Spiritu re fascitrari" from honey by-products: An interesting source of yeast diversity.

The "Spiritu re fascitrari" (SRF) is a typical Sicilian distillate obtained from the by-products of traditional process of honey production. Although some alcoholic fermentation of honey based products have been described, the present research represents the first investigation on the yeast ecology and the physico-chemical characteristics of honey by-products subjected to an alcoholic fermentation followed by distillation. All samples collected during manufacturing process were analysed for the count of total, osmophilic and osmotolerant yeasts. The honeycombs and equipment surfaces showed the presence of yeasts that was 1.7 and 1.1 Log (CFU/mL), respectively. After enrichment, yeast populations increased and a significant increase of yeasts was registered during the alcoholic fermentation (AF), reaching loads higher than 7LogCFU/mL after day 6. A total of 2816 colonies of yeasts were isolated from the count plates and the following species were genetically identified: Lachancea fermentati, Pichia anomala, Pichia kudriavzevii, Saccharomyces cerevisiae, Wickerhamomyces anomalus, Zygosaccharomyces bailii and Zygosaccharomyces rouxii. During the spontaneous AF process, the species S. cerevisiae, Z. bailii and Z. rouxii were mainly isolated and the feed conversion ratio of sugars into ethanol was about 53%; high contents of acetic acid and glycerol were also found. The highest concentrations of volatile organic compounds (VOCs) were registered for esters, alcohols and aldehydes (346.55, 331.041 and 13.65μg/L, respectively). Many VOCs identified as "specific floral markers" such as nonanal and 1-hexanol, 1-octanal and linalool oxide were found. Although more studies are needed, our results suggested that the S. cerevisiae strains isolated in this study must be evaluated in situ for their potential to act as starters for the continuous production of SRF. This because these strains are expected to drive the fermentation process reducing the risk of off-odour and off-flavour formation.