龙眼果实采后容易发生果皮褐变，是影响采后龙眼果实品质和货架期最重要的因素。热处理是一种能延缓果蔬衰老、保持贮藏品质的环保型采后物理处理方法。本文探讨热处理对采后龙眼果实果皮褐变和酚类物质代谢的影响。采后“福眼”龙眼果实用50 ℃热水处理10 min，晾干，用聚乙烯薄膜袋密封包装，置于（15?1）℃下贮藏。贮藏期间定期测定果皮褐变指数、总酚含量、苯丙氨酸解氨酶（PAL）、多酚氧化酶（PPO）和过氧化物酶（POD）活性的变化。结果表明：与对照果实相比，50 ℃热水处理10 min可有效降低采后龙眼果实果皮褐变指数，降低果皮PPO和POD活性，提高果皮PAL活性，保持较高的果皮总酚含量。因此认为，50 ℃热水处理10 min可有效降低采后龙眼果实酚类物质代谢，从而延缓采后龙眼果实果皮褐变的发生。

Harvested longan is susceptible to pericarp browning, which is the most important factor affecting the quality and shelf-life of harvested longan. Heat treatment is an environment-friendly postharvest physical treatment, which can delay senescence and maintain quality of harvested fruits and vegetables. Effects of heat treatment on browning and phenolics metabolism in pericarp of harvested longan (Dimocarpus longan Lour.) were investigated in this paper. The harvested ‘Fuyan’ longans were treated with hot water at 50 ℃ for 10 minutes. Then they were dried, packaged and stored at (15?1) ℃. During storage, browning index, total phenolics content, activities of phenylalanine ammonialyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) in pericarp of harvested longan were determined. The results showed that as compared to the control fruits, the treatment with hot-water effectively reduced browning index, decreased PPO and POD activity, increased PAL activity, and remained higher total phenolics content in pericarp of harvested longan. Therefore, hot water treatment at 50 ℃ for 10 minutes can effectively reduce phenolics metabolism, thereby delaying the occurrence of browning in pericarp of harvested longan.

国家自然科学基金项目（30972070、31171776、31201445）；国家科技支撑计划项目(2007BAD07B06)；高等学校博士学科点专项科研基金项目（20123515120016、20133515110014）；福建省自然科学基金项目（2011J01079、2012J05040）