Using a polynomial model for fungi from table olives

Table olives are one of the most important fermented vegetables in the food industry because of their worldwide economic importance. Enterobacteriaceae, lactic acid bacteria and yeasts are among the most relevant microorganisms involved in olive fermentation determining safety, quality and flavour of the final product. Fungi can play a double role during table olive processing acting as spoilage or desirable microorganisms. This article addresses the effects of some factors (pH, NaCl, temperature, phenols) on the growth/survival of yeasts and moulds, both some wild isolates from olive brine and some yeasts from a public collection (Pichia guilliermondii, P. holstii, Wickerhamomyces anomalus). The research was divided into two steps: a 1st step was aimed at assessing fungal growth by evaluating separately each factor; in a 2nd step, NaCl, pH and temperature were combined through a simple DoE (design of experiment). For this last step, W. anomalus and P. guilliermondii were used as test fungi. Generally, fungi were not inhibited either by temperature, salt or acidic/alkaline pHs. Moreover, the approach of DoE pinpointed that the effect of some factors could experience a shift and change over the time.