Impact of selected wild yeasts starters on the volatilome and phenolic contents of Gordal, Manzanilla and Hojiblanca naturally fermented green olives

The impact of wild yeast starters previously isolated from table olive fermentations and selected for their volatile profile (Pichia kluyveri L13, Kluyveromyces lactis L39 and Wickerhamomyces anomalus L25) and/or its β-glucosidase activity (W. anomalus L25) on the volatilome and phenolic content of natural-style green table olives was investigated. For this, the selected yeast strains were inoculated in brines of natural-style green olives from Gordal, Manzanilla and Hojiblanca cultivars and fermentations were carried out for 6 months. In each case, spontaneous fermentations were carried out in parallel and served as controls. Metagenomic studies showed that the three strains were able to survive along the fermentations and affect the microbial composition of the brines. In all the three olive cultivars, the use of K. lactis L39 as starter resulted in a fermented product with a higher concentration of volatiles associated to pleasant aromas compared to that from the corresponding uninoculated fermentation. Despite W. anomalus L25 was a β-glucosidase-positive strain, its use as starter did not manage to reduce the total phenol content or the oleuropein content in pulp compared to the corresponding uninoculated control, demonstrating that the presence of β-glucosidase activity is not necessarily related to the ability to hydrolyze oleuropein.