ANTIOXIDANT PHENOLICS IN ESCAROLE AND RADICCHIO DURING STORAGE OF FRESH-CUT ´READY-TO-USE´ PRODUCT

Abstract

In this study, escarole (Cichorium endivia L. var. latifolium Hegi) and radicchio 'Rosso di Chioggia' (C. intybus L.) were considered. The phenolic composition and content, the activity of polyphenoloxidase (PPO) and peroxidase (POD) and the antioxidant capacity in vitro were assessed during the storage for nine days at 4°C of the fresh-cut product packed in polyethylene bags in air atmosphere (commercial conditions). Both species showed to be rich in chlorogenic acid, other caffeic acid derivatives and some flavonoids (kaempferol glycosides in escarole and quercetin glycosides in radicchio). Moreover, in radicchio four anthoeyans, one of which particularly abundant (probably identified as kuromanin) were found. The total phenolic content in 'radicchio' was about 4-5 times higher than in escarole. In both species, phenolic compounds showed the tendency to a gradual decrease during storage, followed by an increase more marked in escarole, in which it is evident after the fifth day in storage. Changes in oxidative enzyme activities were in good agreement with phenolic content variation: in particular, PPO activity had the same trend as chlorogenic acid (low initial decrease followed by an increase), whereas POD activity, initially stable, increased after the fifth day in storage, more markedly in escarole and slowly in radicchio. Both species showed a good level of 'antioxidant potential' until the end of the commercially accepted storage period for MPV (seven days in Italy and EU countries). There was some evidence that, after the fifth/sixth day in storage, phenolic compound content increased for the low temperature. So, the nutritional value of the product increased towards the end of its shelf-life (with respect to the antioxidant capacity). This finding will be more important, if in the future it will be possible, due to innovative technologies, to extend by 2-3 days the shelf-life of minimally processed leafy vegetables.