Survival of potential probiotic lactic acid bacteria on fermented green table olives during packaging in polyethylene pouches at 4 and 20 °C

Abstract

The survival of selected lactic acid bacteria (LAB) with in vitro probiotic potential was studied during storage of cv. Halkidiki green olives previously subjected to inoculated Spanish-style fermentation. After fermentation olives were packed in polyethylene pouches, covered with freshly prepared brine (9%, w/v, NaCl), acidified with 2‰ (w/v) citric acid and 1.5‰ (w/v) ascorbic acid, and stored at 4 and 20 °C for 357 days. Four packing treatments were studied, namely olives previously fermented by (i) the indigenous microbiota (control); (ii) Lactobacillus pentosus B281; (iii) Lactobacillus plantarum B282; and (iv) a co-culture of both LAB strains. Microbiological analyses were performed on the olives in parallel with physicochemical changes (pH, titratable acidity, salt content, aw and colour) at the early (day 1), middle (day 197) and final stage (day 357) of storage, as well as sensory evaluation at the end of the storage. The survival of probiotic strains was confirmed by Pulsed Field Gel Electrophoresis (PFGE). LAB decreased throughout storage reaching a final population of ca. 3.5–4.0 log CFU/g and 4.5–5.0 log CFU/g at 4 and 20 °C, respectively. The pH values ranged between 3.90 and 4.61 during storage depending on packaging condition. PFGE analysis revealed that L. pentosus B281 and L. plantarum B282 showed a high survival rate with a recovery of 100 and 96%, respectively, at 4 °C, and less than 20% for both strains at 20 °C. Finally, in the packing treatment with a co-culture of both strains, L. pentosus dominated over L. plantarum throughout storage at both temperatures.