Influence of yeasts on the oil quality indexes of table olives.

After moisture, fat is the major constituent of table olives. However, scarce studies have been carried out to determine the influence of microorganisms and type of processing on the modification of their quality indexes. The present survey studies the influence of lipolytic (Candida boidinii TOMC Y5 and Wickerhamomyces anomalus TOMC Y10) and nonlipolytic (Debaryomyces etchellsii TOMC Y9 and Pichia galeiformis TOMC Y27) yeasts on the oil quality indexes of Manzanilla and Hojiblanca green fruits processed as directly brined and lye-treated table olives. Overall, the inocula scarcely used available sugars, except the lipolytic C. boidinii strain in lye-treated olives. Acetic acid production was limited in all conditions, except for the D. etchellsii strain in directly brined Manzanilla fruits. Ethanol formation was also reduced, although the W. anomalus (in both types of elaboration) and the C. boidinii (in lye-treated olives) strains produced significantly higher proportions. Apparently, changes in the oil quality indexes of processed olives were not related to the presence of yeasts, and hence, could have been caused by the endogenous activity of the fruits. A principal component analysis using the microbiological, physicochemical, and oil quality data supported this hypothesis, grouping treatments according to olive variety and type of elaboration, while segregation due to yeast inocula was not observed.