Impact of processing and storage conditions on color stability of strawberry puree: The role of PPO reactions revisited

The effect of pre-heating fresh strawberries (hot break) and the use of refrigerated temperatures prior to pasteurization on the stability of anthocyanins, vitamin C, color and polyphenol oxidase (PPO) activity during storage (42 days at 35 degrees C) of strawberry puree was studied. Hot break resulted in 20% residual PPO activity and caused 10% anthocyanin degradation, whereas vitamin C was unaffected. After mashing, purees were stored at 4 degrees C and 25 degrees C for 3 h. During this period, anthocyanins and PPO activity remained constant independently of the processing history but ascorbic acid was oxidized faster at 25 degrees C. Pasteurization caused complete inactivation of PPO, reduction of anthocyanins (25%), of a* value (6%) and of vitamin C (50%). Neither partial inactivation of PPO early in the processing (hot break) nor the use of refrigeration prior to pasteurization had a positive effect on color and anthocyanin stability of strawberry puree during subsequent storage, suggesting that PPO-derived reaction products formed during processing have a very limited impact on color degradation during shelf-life.

Automated summary

The study showed that hot break process during puree making may cause some degree of anthocyanin degradation, while refrigeration before pasteurization did not have a significant positive impact on the color and anthocyanin stability of the puree. Pasteurization completely inactivated PPO, leading to reduction in anthocyanins and vitamin C.