Effect of acidification with citric acid on the microbiological, chemical and quality characteristics of natural-style green table olives from Manzanilla and Hojiblanca cultivars

The effect of acidification with citric acid on the microbiological and chemical characteristics and quality attributes of natural-style green table olives of the Manzanilla and Hojiblanca cultivars was investigated. Spontaneous and yeast-inoculated fermentations were performed on samples with added citric acid, and the corresponding non-acidified samples were used as controls. An additional treatment using lactic acid was also included for comparison purposes. Values of pH in all acidified samples were below 4.0 throughout fermentation, but in the controls the pH exceeded the safety limit of 4.3. The growth rate of yeasts in brine was significantly affected by the pH value. No other microbial group was detected in the fermenting brines. Treatment with citric acid was not effective in reducing oleuropein content compared to controls. Differences were found in the chemical composition between the samples treated with citric acid and the controls, these differences being more numerous in the Hojiblanca cultivar. In olives treated with lactic acid, compared to citric acid, the formation of lactate esters and a larger production of succinic acid were highlighted. Acidification with citric or lactic acid had no impact on the firmness and color parameters of Manzanilla olives, but significantly affected color of the Hojiblanca olives.