鲜切雷竹笋冷藏过程中木质化机理的研究

研究鲜切雷竹笋在4℃冷藏条件下苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活力及丙二醛(MDA)、多酚、木质素含量的变化规律，探讨其木质化机理。结果显示：在冷藏过程中，PAL、POD活力、MDA含量呈先上升，后下降的趋势；PPO活力在前6d缓慢上升，第15天开始下降；多酚含量在冷藏前6d急剧下降，后缓慢上升，第12天又开始下降；木质素含量不断增加，基部为5%～26%，中部为3%～24%，尖部为2%～22%。结果表明：在冷藏期内，PAL、POD活力大幅度增加，是导致鲜切雷竹笋木质化的关键酶；酚类物质作为木质素合成的前体物质，参与木质素的合成；MDA可能参与鲜切雷竹笋的木质化进程，但需进一步验证；木质素含量从基部向尖部逐渐降低，木质化进程是从基部向尖部推进的。

Lignification Mechanism of Fresh-Cut Bamboo Shoots during Cold Storage

The activities of phenylalanine ammonialyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) and the contents of malondialdehyde (MDA), polyphenol and lignin in fresh-cut bamboo shoots stored at 4 ℃ were measured and the lignification mechanism was explored. The results indicated that the activities of PAL and POD and MDA content tended to increase and then decrease with increasing storage time. PPO activity slowly ascended during the first 6 days, and began to descend on the 15th day, whereas polyphenol content sharply declined during the first 6 days, then slow rose, and began to decline again on the 12th day. Lignin content showed a continuous increase, which was 5%－26% in the bottom, 3%－24% in the middle and 2%－22% in the top. These data suggest that the activities of PAL and POD considerably increase during cold storage, which are the key enzymes in the lignification of fresh-cut bamboo shoots. Moreover, phenolic compounds are involved in the synthesis of lignin by providing precursors. Meanwhile, MDA may also be involved in the lignification of fresh-cut bamboo shoots, which needs further identification. Lignin content gradually decreases from the bottom to the top of bamboo shoots, implying the lignification process proceeds from the bottom to the top.