Purpose: To evaluate the ability of lactic acid bacteria with probiotic properties used as starters in olive fermentation to retain adequate populations during the shelf life of fermented green table olives under modified atmospheres.
Methods: Samples of 100 g of fermented green olives cv. Halkidiki, were packed in polyethylene pouches in modified atmospheres (70% N2:30% CO2) and stored at 4 and 20 °C for 12 months. The experiment consisted of four packaging treatments with olives previously fermented by: indigenous microbiota (C), Lactobacillus pentosus (A), Lactobacillus plantarum (B), and mixture of both strains (S). The inoculated strains have been previously selected for retaining in vitro probiotic potential. Microbiological (lactic acid bacteria-LAB, yeasts/molds), physicochemical (pH, acidity, salt content, color, firmness) and sensory analyses were conducted throughout storage. The survival and the variability of the LAB strains were assessed by pulsed field gel electrophoresis (PFGE).
Results: The population of LAB at the beginning of storage was 5.5-5.9 log CFU/g. At the end of storage period, the population of LAB at 4 °C decreased up to 0.5 log CFU/g, depending on the case, whilst at 20 °C increased approximately 1 log CFU/g in the cases A and S, 0.5 log CFU/g in B and remained stable in C. According to the PFGE, the survival of the inoculated strains was higher for Lb. pentosus, depending on the case and the storage temperature. According to the sensory and physicochemical analyses, the quality characteristics of the olives were better preserved at 20 °C.
Significance: Fermented green olives with lactic acid bacteria exhibiting probiotic potential were found to contain adequate amounts (106-107 CFU/g) of the inoculated starters even after a 12 month storage, retaining desirable sensory characteristics.
This study was funded by the EU project PROBIOLIVES (FP7-SME-2008-2-243471)