Effect of starter cultures on fermentation of naturally and alkali-treated cv. Conservolea green olives

The effect of starter cultures, i.e. a commercial (CM, based on Lactobacillus pentosus appropriate for olives fermentation) and an autochthonous (OSC, developed by oleuropeinolytic strains belonging to the Lactobacillus plantarum group, isolated from olives) on the microbiological profile and physicochemical traits during the fermentation of naturally (untreated) and alkali-treated cv. Conservolea green olives was studied in comparison to uninoculated spontaneous fermentation (SP, control). In addition, the reduction of the natural bitterness of the product during processing was assessed. Lactic acid bacteria in OSC treatment were dominated faster and grown in higher populations than CM or SP during the first ten days of the fermentation, resulting in a more intense drop of the brine pH leading to a faster fermentation. Fruit phenolic compounds and antioxidant capacity decreased more in alkali-treated than in naturally processed olives. In alkali-treated olives the bitter taste was not detectable regardless the fermentation process applied. However, in the naturally processed olives the OSC treatment resulted in a medium-low while CM or SP in medium to medium-high bitter taste, indicating that the use of OSC might be a promising tool for the efficiency of processing of naturally green olives.