Evaluation of polyphenol decay in the oily fraction of olive fruit during storage using a mild sample handling method

A mild sample handling method able to minimize polyphenol degradation due to endogenous enzymes during the sample preparation permitted the assessment of polyphenol decay in the oily fraction of the olives during their storage before processing. During 7 days of storage at 15°C, the concentration of polyphenols in the olives was stable in vegetation water, whereas in the oily fraction of the fruits it remained almost constant in the first 3 days and then decreased rapidly. The polyphenol decay of the oily fraction of the stored olives can be attributed to the oxidoreductase enzymes of the fruit as well as those produced by the microbiota grown in the carposphere during storage. The activity of phenoloxidase in the olive pulp decreased drastically in the first 2 days of storage, and then decreased gradually, whereas peroxidase activity showed a gradual reduction throughout the entire storage period. The microbiological analysis showed a rapid increase of bacteria and yeast number during the first 4 days, then the values leveled out during the storage period. Phenoloxidase activity of microbic origin was low during the first 3 days then increased rapidly, whereas peroxidase activity increased during the first 3 days then leveled out to the same values for the duration of the storage time. Practical applications: The mild sample handling method of extraction studied was able to minimize olive oil polyphenol degradation during the sample preparation due to the endogenous enzymes of the olive fruits. The use of this method allows for the improvement of virgin olive oil quality, through the assessment of polyphenol concentration decay during all the stages of olive oil production, including that of fruit storage before processing.