Possible Influences of Water Loss and Polyphenol Oxidase Activity on Anthocyanin Content and Discoloration in Fresh Ripe Strawberry (cv. Oso Grande) During Storage at 1 °C

F : F : F : F : Fresh ' '' ''Oso Grande' strawberr awberr awberr awberr awberries wr ies wr ies wr ies wr ies wrapped in polyvinyl chlor apped in polyvinyl chlor apped in polyvinyl chlor apped in polyvinyl chlor apped in polyvinyl chloride str ide str ide str ide str ide stretch film lost 0.7% of their initial etch film lost 0.7% of their initial etch film lost 0.7% of their initial etch film lost 0.7% of their initial etch film lost 0.7% of their initial weight during storage for 8 d at 1 °C, whereas unwrapped fruit lost 11%. Greater water loss was associated with weight during storage for 8 d at 1 °C, whereas unwrapped fruit lost 11%. Greater water loss was associated with weight during storage for 8 d at 1 °C, whereas unwrapped fruit lost 11%. Greater water loss was associated with weight during storage for 8 d at 1 °C, whereas unwrapped fruit lost 11%. Greater water loss was associated with weight during storage for 8 d at 1 °C, whereas unwrapped fruit lost 11%. Greater water loss was associated with darker and less red fruit, lower concentrations of anthocyanins and other soluble phenolics, and higher polyphenol darker and less red fruit, lower concentrations of anthocyanins and other soluble phenolics, and higher polyphenol darker and less red fruit, lower concentrations of anthocyanins and other soluble phenolics, and higher polyphenol darker and less red fruit, lower concentrations of anthocyanins and other soluble phenolics, and higher polyphenol darker and less red fruit, lower concentrations of anthocyanins and other soluble phenolics, and higher polyphenol o o o oxidase (PPO) activity xidase (PPO) activity xidase (PPO) activity xidase (PPO) activity xidase (PPO) activity. Anthocyanin degr . Anthocyanin degr . Anthocyanin degr . Anthocyanin degr . Anthocyanin degradation and o adation and o adation and o adation and o adation and oxidation of soluble phenolic compounds xidation of soluble phenolic compounds during storage. Proper handling to reduce water loss during postharvest operations should be used to maintain during storage. Proper handling to reduce water loss during postharvest operations should be used to maintain during storage. Proper handling to reduce water loss during postharvest operations should be used to maintain acceptable color of strawberries during shipping and retailing. acceptable color of strawberries during shipping and retailing. acceptable color of strawberries during shipping and retailing. acceptable color of strawberries during shipping and retailing. acceptable color of strawberries during shipping and retailing. K K K red color of strawberry fruit is due to the presence of anthocyanin pigments in the fruit epidermis and cortex. Pelargonidin-3-gluco- side (PGN) and cyanidin-3-glucoside were identified as the main monomeric anthocyanins of strawberry fruit. PGN comprises 80% of the total anthocyanin content in strawberry while cyanidin-3- glucoside is present in smaller amounts (Bakker and others 1994). Strawberry pigments, like other anthocyanins, are relatively un- stable and may easily lose their bright color due to degradation by oxidative enzymes such as polyphenol oxidase (PPO), which is primarily localized in the cortex of strawberry fruit with the antho- cyanins and other phenolics (Lopez-Serrano and Ros Barcelo 2001). In fact, browning in fruits is primarily attributed to PPO activity, which is able to act on phenolic compounds in the pres- ence of oxygen (Nicolas and others 1994). PPO catalyzes the hy- droxylation of monophenolics, leading to the formation of o- diphenol compounds and to the oxidation of o-dihydroxy compounds to quinones. The quinones subsequently undergo polymerization, producing characteristic yellow to brown colors in the fruit tissue (Mayer and Harel 1979; Spanos and Wrolstad 1992). Changes in anthocyanins seem to be one of the causes of fruit browning, and their degradation is the result of coupled ox- idation by PPO in the presence of other phenolic compounds (Wesche-Ebeling and Montgomery 1990; Kader and others 1999; Jiang 2000; Zhang and others 2000). These authors suggested that oxidation and polymerization reactions of anthocyanins with PPO- produced quinones and intermediate oxidation products, rather than direct PPO action on anthocyanins, may play a role in antho- cyanin losses and color changes in processed fruits. However, little is known about the development of superficial browning in fresh