Phytochemical composition and antioxidant stability of fortified yellow passion fruit (Passiflora edulis)
2003
Yellow passion fruit juice (PFJ, Passiflora edulis f. flavicarpa) is an important component of many tropical fruit beverages, but limited data exist on its antioxidant chemical composition and stability during processing and storage. PFJ fortified with ascorbic acid (450 mg/L) and sucrose (10%) was compared to a nonfortified control, and each was evaluated with and without vacuum deaeration to remove dissolved oxygen. Following pasteurization, juices were stored for 28 days at 37 degrees C to accentuate physicochemical changes. Pasteurization (85 degrees C for 30 min) resulted in minor changes to physicochemical attributes, but appreciable changes occurred during storage that resulted in termination of the study after 28 days. Oxygen control strategies proved to be ineffective for quality retention and indicated oxygen-independent reactions affecting juice color, phytochemical content, and antioxidant activity. Ascorbic acid and sucrose fortification had an overall preservation effect on total carotenoids, the former resulting in hyperchromic shifts in absorbance, indicating their chemoprotection. Pasteurization resulted in a 25% loss in L-ascorbic acid, which was completely destroyed after 14 days of storage; losses coincided with increased juice browning and formation of 5-hydroxymethylfurfural. Numerous polyphenolics were present in PFJ, and 16 of them were tentatively characterized on the basis of spectral similarities to known standards. Individually, polyphenolics increased during pasteurization, only to decline during storage at elevated temperatures. Antioxidant activity was measured in PFJ and in two subfractions (hydrophilic and lipophilic) after processing and storage, but antioxidant values were nonadditive. A significant chemical interaction affecting antioxidant capacity was found for hydrophilic juice components, but none was observed in the presence of lipophilic phytochemicals. Physicochemical attributes and overall quality of PFJ were retained following pasteurization but were significantly impacted by degradative reactions during accelerated storage.
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