Preliminary studies on phenolic behavior in lyophilised olives

The widespread recognized health benefits of Mediterranean diet are also due to the consumption of virgin olive oil and its nutraceutical properties mainly related to peculiar phenolic compounds. The numerous studies regarding this class of secondary metabolites have been boosted in the last decades. Unfortunately, only a very small fraction of the phenolic compounds of the olives is extracted in virgin olive oil, while, after olive crushing, the unextracted fraction and is partially degraded by chemical or enzymatic pathway and part remains in the waste. The main enzymes involved in this degradation are β-glucosidase, esterase, polyphenoloxidase and peroxidase and their action is strongly mediated by the presence of the constitutional water of the fruit [1, 2]. The water in fresh olives is close to 50% of the weight. As a consequence, the storage conditions of the olive before milling can influence the enzymatic activity and the phenolic profiles of the extracts from olive pastes and olive oil. The aim of this work was to study the changes of phenolic content in olive pastes obtained by fresh, frozen and freeze-dried fruits and to clarify some biosynthetic aspects related to secoiridoids over ripening. The three Tuscan cultivars Frantoio, Moraiolo and Leccino have been studied working on samples from 2011 and 2012. The results have shown a strong increase of the total phenolic content in all the extracts obtained by freeze-dried olives for all the cultivars in every ripening period when compared with the corresponding fresh fruits. The research was also focused to identify alternative uses of the olive flours obtained by unripe dried fruits .The stability over time of the fine powder obtained from the freeze-dried fruit and its high phenolic content suggest the possible use of this product as ingredient for functional foods or food supplements for humans.