Effect of different brining treatments on the fermentation of cv. Conservolea green olives processed by the Spanish-method

The effect of different initial brining conditions on the spontaneous fermentation of cv. Conservolea green olives was studied. The different treatments included: (a) brine acidification with 2‰ (v/v) lactic acid (control), (b) addition of 25‰ (v/v) 1 n HCl (c) substitution of the initial brine by 20% (v/v) with a brine from a previous fermentation (brine re-use). Microbial growth, pH, titratable acidity and organic acids were monitored. Brine re-use process was the most effective in minimizing the likelihood of spoilage since it decreased the survival period of enterobacteria (24 days), followed by the HCl treatment (28 days) and the control (35 days). However, after 35 days of fermentation, pH values reached a plateau above 4.8 in all treatments indicating that supplementary treatments were necessary to enhance lactic acid fermentation and attain acidity/pH levels that would improve the physicochemical characteristics of the final product and ensure its safety. Addition of 1.5% (w/v) glucose in the HCl-treated and brine re-use processes as well as 5‰ (v/v) lactic acid in the control was performed. All supplementary treatments were effective in reducing pH to a final value of 4.3-4.5. However, glucose increased the final concentration of lactic acid in brine re-use and HCl-treated processes (73.4 and 67.8 mm, respectively) compared with the control that was lacking in acidity (44.7 mm), denoting a clear advantage of glucose over lactic acid as a supplement.