Profile of anti-lactic acid bacteria compounds during the storage of olives which are not treated with alkali

Abstract

The objectives of this study were: (1) to characterize the phenolic and oleosidic compounds in the preservation solutions of black ripe olives, particularly those with antimicrobial activity and (2) to explain the growth of lactic acid bacteria (LAB) in the olive brines. Fruits were put into industrial tanks and preserved in acidified solutions under aerobic or anaerobic conditions. Lactic acid was analyzed as a marker of LAB growth in the olive brines. Hydroxytyrosol was the most concentrated phenolic compound in these solutions followed by hydroxytyrosol 4-glucoside, hydroxytyrosol 1-glucoside, tyrosol and salidroside. Among the oleosidic compounds, secoxyloganin and oleoside 11-methyl ester were found in a concentration between 0.3 and 3 mM, whereas secologanoside and oleoside were always detected at a concentration below 0.2 mM. Likewise, a notable concentration of the dialdehydic form of decarboxymethyl elenolic acid either free or linked to hydroxytyrosol was found at the beginning of preservation, which was high enough to inhibit LAB growth. However, an acidic degradation of these antimicrobials occurred with time, particularly in the summer, and it allowed for the growth of lactobacilli and the formation of lactic acid. The results of this study are a contribution to explain the microbial fermentation in acidified solutions of olives which are not treated with NaOH on an industrial scale.