Stability in by-product formation as a strain selection tool of Saccharomyces cerevisiae wine yeasts

A strain of Saccharomyces cerevisiae homozygous for different physiological and metabolic characters was inoculated into two grape musts and the stability of the characters was tested by isolating clones at different fermentation stages. A total of 60 cell-clones were collected and asci dissected from each, yielding a total of 1200 single spore cultures, which were then tested for the segregation of several genetically controlled traits. From the parental strain, 10 asci were dissected and the 40 single spore cultures obtained were used as controls. Micro-fermentations were performed with the 200 single spore cultures obtained from clones isolated at the end of Trebbiano and Aglianico must fermentations. The majority of these spore cultures produced amounts of the secondary compounds at the same level as the parental strain. The progeny of three clones from the Trebbiano fermentation exhibited a significant increase in the production of isoamyl alcohol, whereas the progeny of one clone from the Aglianico fermentation differed in the production of acetoin and amyl alcohols. The variability found in the levels of by-products can also affect the organoleptic properties of the final product. The introduction of the 'metabolic characteristics stability' as a selective index for industrial strains is advised.