Effect of pre‐treatment and freezing on the polyphenol oxidase activity and color stability of sliced peaches

A study was conducted to determine the polyphenol oxidase (PPO) activity and changes in surface color and hydroxymethylfurfural (HMF) content in fresh and pre-frozen peach slices stored at different temperatures. In this study, fresh (F) and pre-frozen (P) peaches were subjected to one of four treatments: (i) no treatment (N); (ii) blanching in boiling (96 °C ± 4 °C) water (B); (iii) dipping in 2% l-ascorbic acid and 2% citric acid (AC); or (iv) blanching placed in boiling water, cooling and dipping in 2% ascorbic acid and 2% citric acid (BAC). Peaches from each treatment group were held at -7, -9, or - 12 °C for 21 days.After 21 days of storage, PPO activity and browning was greater in peaches stored at -7 °C than the PPO activity and browning of peaches stored at -9 °C and - 12 °C. Overall, lightness (L*), yellowness (b*), chroma (c*) and hue (h*) decreased while redness (a*) increased during storage. The BAC peaches had less discoloration and lower PPO activity than peach slices exposed to other treatments. Non-enzymatic browning (HMF indicator) was more pronounced for blanched peaches during storage than unblanched peaches. Pretreatment of blanched peaches with ascorbic and citric acid reduced browning during 21 days at frozen storage for peaches held at -9 °C or - 12 °C.Storage at -12 °C significantly reduced browning and HMF formation in both blanched and unblanched peach slices in comparison with -7 °C storage. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.