Towards Controlled Fermentation of Table Olives: LAB Starter Driven Process in an Automatic Pilot Processing Plant

Abstract

The results of an experimental trial, carried out using a specifically prepared microbial starter, in an automated pilot plant, are presented. The microbial starter was composed by Lb. pentosus strains. The automatized process was compared with natural fermentation in plastic vats, as control. Relevant process parameters, chemico-physical determinations, instrumental texture, and microbiological analyses were carried out to monitor the fermentation process. Driving the process in controlled conditions resulted in a more rapid acidification, pH reaching lower values than the control. In controlled conditions, inoculated lactobacilli carried out a fast colonization supplanting more rapidly spoilage microflora. In started samples, yeasts number increased until reaching 5 log at 60 days, keeping this value constant until the end of the trials, while, in control batches, their growth was more rapid, reaching 5 log from 15 to 30 days, but their number decreased to 3 log at 90 days. The two processes produced olives with comparable texture profile. However, olives coming from the controlled process resulted debittered in 3 months (descriptive sensory analyses and oleuropein quantification in HPLC), while naturally fermented olives resulted not yet debittered at the end of the trial (180 days). Slight differences were found in few other sensory descriptors. Our results showed that, along with the use of effective autochthonous microbial starters, the innovation of processing plants is the next step towards the shortening of the processing time and the safety assurance of the product, while retaining the sensory quality of naturally fermented olives, using an environmentally friendly technology.