Fermented olives (Olea europaea L.): A detailed insight into morphological changes and phenolic profile from harvest to jar

The aim of this research was to determine the changes in fruit quality parameters, antioxidant capacity and phenolic content during natural fermentation of five olive cultivars. During processing, the fruit weight and firmness decreased and dry matter increased in all cultivars. Nine phenolic compounds were studied in detail during natural fermentation for the first time. 'Istrska belica' have the highest contents of phenolics, which require the longest processing period. Oleuropein content decreased during processing in all cultivars, resulting in fruit browning, a decrease in antioxidant capacity and an increase in other derived phenolic compounds. We found that the contents of bitter phenolic compounds stabilized a few months before the end of processing and the bitter taste in the final products did not differ between cultivars, although their content varied between cultivars. Understanding phenolic variations during the olive processing could reduce processing time and increase phenolic content in the final product.