貯藏溫度及採收成熟度對‘新雪'梨果皮黑變與苯丙胺酸脫氨裂解酶及多酚氧化酶活性變化之影響

Effects of Storage Temperature and Harvest Maturity on Skin Blackening and the Activities of Phenylalanine Ammonia Lyase and Polyphenol Oxidase in Japanese Pear (Pyrus pyrifolia Nak. var. Shinsetsu)

本文探討貯藏溫度及採收成熟度對‘新雪’梨之果皮黑變與苯丙胺酸脫氨裂解酶（PAL）及多酚氧化酶（PPO）活性變化之影響。梨果貯藏於1、5、9及13℃中5週，在1℃者發生明顯可見的果皮黑變，這是低溫寒害的結果。果皮的黑變會伴隨著PAL與PPO活性的增加而加劇，亦以貯藏於1℃中最為明顯。此外，採收成熟度會影響果實黑變的程度；相較於低成熟度及高成熟度的梨果，中成熟度者的果皮黑變最輕微。經16週連續低溫貯藏，3個不同採收成熟度的果皮都有黑變現象，以高成熟度者最嚴重。雖然中成熟度果實的最高黑變面積百分比較低成熟度者為少，但中成熟度者正常果實之數量卻比其它2個成熟度者為多。低溫逆境誘導梨果PAL及PPO活性的轉變，可能造成果皮的黑變。而且，梨果實經低溫貯藏後的果皮黑變程度，與PAL及PPO活性間，具有很高的相關性。 The influences of storage temperature and harvest maturity on skin blackening and the activities of browning enzymes: phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) of Japanese pear (Pyrus pyrifolia Nak. var. Shinsetsu) was investigated. Fruits were stored at 1, 5, 9, and 13℃ for 5 weeks. Visible chilling injuries (CI) mainly skin blackening of fruits were occurred seriously at 1℃. An increase in PAL and PPO activities was related to the incidence of skin blackening symptoms. The increase in PAL and PPO activities occurred more rapidly at 1℃ than at 5, 9, and 13℃. Additionally, fruit maturity significantly enhanced skin blackening development; middle maturity fruits developed less skin blackening injury than lower or higher maturity fruits. After 16 weeks continuous low temperature storage, skin blackening symptom was occurred in all treatments, but more seriously in higher maturity fruits. Although skin blackening area in middle maturity fruit was lower than that of low maturity fruit, however, its numbers of normal fruit were the highest among three maturities. The results indicated that low temperature stress induced concerted activities of PAL and PPO, which might result in skin blackening of pear fruits. However, the appearances of skin blackening development of pear fruits after low temperatures storage was highly correlated to the response of PAL and PPO activities to chilling.