影响鲜切马铃薯褐变相关酶及底物的研究

Study on the Browning-related Enzymes and Substrates of Fresh-cut Potatoes

摘要:

本文通过对克新4号和克新13号马铃薯鲜切贮藏期间，褐变相关酶活性、相关底物的比较研究，探讨鲜切马铃薯褐变机理。结果表明：鲜切后1 h，克新4号即出现轻微褐变，4 h后褐变明显，而克新13号鲜切后12 h仍具有较好颜色，2 d后出现轻微褐变。两个品种马铃薯汁液颜色在初始时比较接近，而25 min后汁液颜色差异明显，克新4号褐变程度明显重于克新13号。褐变重的马铃薯，PPO活性高。切割后贮藏期间，克新4号PPO活性始终高于克新13号。克新4号酪氨酸酶活性高于克新13号，POD活性始终低于克新13号，两个品种的PAL活性差异不显著（p<0.05）。褐变相关的主要底物可能是原儿茶酸，不是绿原酸。机械伤害增加了膜脂过氧化作用，导致了丙二醛含量的升高。

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.