Uneven enzymatic browning on fresh-cut apple and its measurement
Cut-surface color is one of the most important appearance factors for customer purchase decisions. Browning on the cut surface, which involves action of polyphenol oxidase (PPO), occurs when fresh-cut fruit is prepared and continues during storage in the presence of oxygen. Uneven browning on the flesh and core of apple may result from uneven distribution of phenolics and PPO. The aims of this study were to determine PPO activity and the amount of phenolics in 'Granny Smith' apple core and flesh and to measure browning discoloration in both crude enzyme extract and the cut apple surface. The effects of inhibitors (sodium chloride, citric acid, ascorbic acid, and their mixtures) on enzymatic browning retardation using endogenous and exogenous substrates were also investigated. The results showed an uneven distribution of PPO, phenolic and flavonoid content in apple. Higher enzyme specific activity was found in the core, while larger amounts of phenolics were found in flesh. Color change and browning index (BI), over 3.5 h, on the cut surface of apple treated with inhibitors were lower than those of the control (no treatment). Apple core had higher BI compared with flesh. Exogenous substrate was more specific towards PPO compared with endogenous substrate. The Trichromatic Color Analyzer (TCA) system was used to monitor color appearance, including lightness, chroma and hue, during continuing brown discoloration on the cut apple surface. Results at the time of the first measurement and after 610 min showed that mixed inhibitors could reduce in chroma shift more than lightness and hue shifts. TCA confirmed that greater uneven color distribution increased with time.
Duangmal, K., Worapotpisut, C., Romposa, N. and Katemake, P. (2017). Uneven enzymatic browning on fresh-cut apple and its measurement. Acta Hortic. 1179, 69-76
fresh-cut, browning, polyphenol oxidase, Trichromatic Color Analyzer system, color difference