Establishment of conditions for green table olive fermentation at low temperature

Abstract

Four Lactobacillus plantarum strains were isolated from table olive cold fermentation brines. Their specific growth rate and acidification in MRS broth and in green table olive brines were studied by means of a mixed 2 pH (4.5 and 5.0)×3 salt (3, 4 and 5%, w/v, NaCl)×3 incubation temperature (9, 12 and 15°C) levels factorial design. In MRS broth, the greatest effect (linear) on acidification was due to temperature. In brine, the effects were considerably less, pH (linear) being the most important for specific growth rate, and temperature (linear) for acidification. In both media, an initial pH of 5.0 led to good acidification at 12–15°C. The effectiveness of the conditions found (initial pH of 5.0; 3%,w/v, NaCl; and incubation at 12°C) was confirmed in simulated green olive fermentations with three of the strains, which proved especially robust. Behaviour in terms of growth and acidification rates was similar for these strains, and comparable to that observed in traditional processes, although mannitol and sucrose were not metabolised and fructose was only partially used. This leads to the possibility of obtaining normal fermentation processes of table olives in cold regions when appropriate initial conditions and starter cultures are used.