INDUCED LACTIC-ACID FERMENTATION DURING THE PRESERVATION STAGE OF RIPE OLIVES FROM HOJIBLANCA CULTIVAR

The influence of initial sodium chloride concentration (6 and 0%, w/v), acetic acid concentration (0.6, 0.3 and 0.0%, v/v), type of process (natural and inoculated), and storage system (anaerobic and aerobic) on the inducement of a lactic fermentation for the preservation stage of Hojiblanca cultivar ripe olives was investigated. The addition of 6% NaCl prevented colonization by lactic acid bacteria in all cases. A high level of acetic acid (0.6%) was effective in preserving olives for 2 months, although yeast growth was not inhibited for longer periods of storage. Natural growth of Lactobacillus plantarum did not occur. Inoculation with this micro-organism was effective only in the two treatments with tap water (with no NaCl) as the initial covering solution, although survival was reduced to a half of the added organisms when the initial pH was corrected with 0.3% acetic acid. In these two treatments pH quickly reached appropriate values ( < 4.0) for olive stabilization. Aerobic conditions led to low concentrations of carbon dioxide, without disturbing growth of lactic acid bacteria. Thus, the aerobic lactic acid fermentation, with tap water initially, was the most adequate preservation procedure for the storage of ripe olives prior to their oxidation treatment. Results of trials conducted on an industrial scale showed the same pattern and confirmed the viability of the new procedure.