Study of the variation of the phenolic and polyphenolic content and of the antioxidant capacity of extracts obtained from osmotically pre-treated and frozen fruits

Over last years consumers are paying more and more attention to a diet rich in fruits and vegetables that assure a proportionate intake of antioxidant compounds such as carotenoids, tocopherols, ascorbic acid, flavonoids and other phenolic compounds. Several scientific studies proved the efficacy of these minor compounds of foods in contrasting or slowing down degenerative and cardiovascular diseases. Freezing is a useful technology for preservation of nutritional compounds of food over long periods; but thawing causes a dramatic decrement of organoleptic and nutritional characteristic due to the high content of water in fruits. Several technologies, based upon osmotic processes (OD, PVOD, VI, ICF, etc.) could be used as pre-treatment, in order to improve fruit performance in freezing/thawing processes. This work reports results on the preservation of antioxidant capacity (based on ABTS radical cation test) and phenolic content (determined by HPLC) of some fruits (apples, nectarines and strawberries) osmotically pre-treated and subsequently frozen. Results show that these technologies could preserve phenolic content of fruits along with the storage period and during thawing for direct consumption.