Study on the Browning-related Enzymes and Substrates of Fresh-cut Potatoes
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Abstract:
This study compared the browning-related enzyme activity and substrates of freshly-cut Kexin No. 4 and Kexin No. 13 potatoes during storage, and discussed their browning mechanisms. The results showed that Kexin No. 4 potatoes exhibited slight browning 1 h after cutting and obvious browning after 4 h, while Kexin No. 13 potatoes retained good color 12 h after cutting and browned slightly after 2 d. The color of the juice from the two species was similar initially, but differed significantly after 25 min, with Kexin No. 4 juice being significantly browner than that of Kexin No. 13. Kexin No. 4 potatoes showed high polyphenol oxidase (PPO) activity. During storage after cutting the PPO activity of Kexin No. 4 potatoes was consistently higher than that of Kexin No. 13 potatoes. Additionally, the tyrosinase activity of Kexin No. 4 potatoes was always higher than that of Kexin No. 13 potatoes, and the peroxidase (POD) activity of Kexin No. 4 potatoes was lower than that of Kexin No. 13 potatoes. The phenylalnine ammonialyase (PAL) activities of both did not differ significantly (p<0.05). Protocatechuic acid, and not chlorogenic acid, may be the enzymatic browning substrates because mechanical damage, produced by cutting, can lead to enhanced peroxidation of membrane lipids resulting in increased malondialdehyde (MDA) content after cutting.
