Olive Fermentation and Processing: Scientific and Technological Challenges

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ABSTRACT: The 3 main commercial table olive preparations are the Spanish‐style green olives, the Greek‐style naturally black olives, and the Californian‐style black ripe olives. In all cases, fruits undergo fermentation in brine solution, which preserves them and increases palatability. Lactic acid bacteria dominate in brines of green olives, while mainly fermentative yeasts are found in brines of black ones. The fermentation is spontaneous and begins as soon as olives are put into brine. Research on table olives has been going on for 100 years, but many questions remain. Previous work has focused on the efficient utilization of starter cultures in order to control the fermentation, to guarantee the absence of spoilage, and to govern the relationship between olive flavor and microorganisms. Nowadays, there is concern over environmental problems that the fermentation solutions represent, in particular their high NaCl content. Fermentation or simply storing olives in water without salt presents some problems. The high concentration of sodium benzoate used for storing black ripe olives by the American industries is not advisable for European processes due to the residual amount of preservative in the final product. Fermentation of green olive wash waters, in order to obtain valuable products, is being pursued, but polymeric inhibitors are problematic and undesirable microorganisms grow. The consumption of organic foods is increasing and black olives fit the definition since they are processed without chemical treatment. However, the hydrolysis of the bitter compound oleuropein, either by microorganisms or acids, needs to be studied.