【作者】 肖红梅；

【导师】 周光宏；

【作者基本信息】 南京农业大学 ， 食品科学， 2003， 博士

【摘要】 贮前热处理可以减轻冷敏感果蔬冷害的发生，提高产品的贮藏性能，然而热处理的作用机理一直未明，成为研究的热点之一。本实验以樱桃番茄(Lycopersicu esculeatum Var．cerasifome)金桔品种为实验材料，研究了热处理对果实后熟生理的影响，同时研究了热处理对活性氧代谢和不同形态不同类型多胺的作用，以探讨贮前热处理减轻番茄冷害的机理。 1．30-48℃的热水处理10-60min，晾干，1±1℃(RH80％-95％)冷藏14天后，置于20℃后熟，以未经热水处理冷藏14天和未冷藏直接置于20℃后熟的果实为对照。结果表明，30-38℃热水处理1h能够保持膜的完整性，减少后熟腐烂，保持良好的食用品质，减轻冷害；而42-48℃的热处理则会对果实造成热伤害，增加果实的腐烂。其中以38℃处理1h抑制冷害的效果最佳。 2．用38℃的热水处理1h，晾干，1±1℃(RH80％-95％)冷藏37天后，置于20℃后熟。结果表明，热处理果实的后熟率为90.0％，而对照只有31.8％；贮前热处理有效地减轻冷害，并减少果实后熟期间的失重；显著增加番茄后熟期间多聚半乳糖醛酸酶(PG)和1-氨基环丙烷-1-羧酸(ACC)合成酶(ACS)的活性，促进ACC、乙烯合成和果实呼吸。热处理可能通过调节乙烯的生成量促进冷藏果实的后熟。 3．对照果实的抗坏血酸过氧化物酶(APX)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性在冷藏初期上升，后期下降。热处理增加SOD活性，不改变变化曲线；提高CAT、APX活性，并在整个冷藏期间保持高活性；而热处理果实POD活性在冷藏期间变化较小。由此推测，贮前热处理通过提高并维持冷藏期间抗氧化酶活性，从而减少过氧化氢的积累，降低氧化胁迫，保持细胞膜稳定，防止果实冷害。 4．热处理抑制果实内源游离态多胺(f-PAs)的累积，成倍增加结合态多胺(c-PAs)水平，对束缚态多胺(b-PAs)总量无影响，显著增加内源亚精胺(Spd)和精胺(Spm)的总量。由此推测热处理可能通过增加Spd和Spm含量，促进结合态多胺形成，以减轻番茄冷害。 5．外源腐胺(Put)和Spm处理后，Put、Spd和Spm总量增加，结合态多胺显著增加，膜泄漏减缓，果实的冷害减轻。由此推测Spm的增加，可以提高果实的耐寒能力，果实冷害下Spm的积累可能是防卫反应；同样Put处理有利于减轻番茄的冷害，博士论文:贮前热处理减轻番茄冷害机理的研究但其作用效果低于SPm. 6.甲基乙二醛双(鸟嗓吟膝)(MGBG)处理，可减少番茄c一Pas总量，不影响b一Pas总童.菲咯琳处理后果实b一PAs大大减少;。一PAs初期增加，后期显著减少.MGBG和菲咯琳处理显著加大膜的渗透和果实的冷害.由这些结果推测维持一定的束缚态多胺水平是减轻番茄冷害的前提，在此基础上提高结合态多胺的含量则可以降低果实的冷害. 以上结果推测热处理通过增加番茄SPd和sPm含量，促进游离态多胺向结合态多胺转变，和提高杭氧化酶的活性，来保持细胞膜的稳定，减轻番茄冷害.更多还原

【Abstract】 Heat treatment has been used for increasing the resistance of the fruit to chilling injury (CI),and also for improving storability. The mechanisms involved in the beneficial effects of heat treatment and the physiological basis associated with CI, however, still remain unclear. The objectives of this study were to evaluate the effectiveness of prestorage hot water, treatment to reduce CI and postharvest physiology, and whether these effects were related to changes in antioxidantion and contents of various types of polyamines (PAs). The effect of hot water treatment on chilling index, ripening index, electrolyte leakage, activities of SOD, CAT, APX, POD, ACS and PG, firmness, respiratory rate, ACC, ethylene, polyamines and so on in mature-green tomato fruits (Lycopersicu esculentum var. cerasifome) stored at 1C, 85%-90% RH before ripening at 20C were evaluated.1. Mature-green tomato were treated in water at 30-48 C for 10-60 min, and then ripened at 20C or stored at 1+1C for 14 days before ripening at 20C. It is found suitable hot water (30-38C) significantly reduced chilling injury and decay, whereas high temperature (42-48 C) increased decay. The treatment which tomato were treated at 38C for 60 minutes is the most effective one on reducing chilling injury.2. Mature-green tomato were treated in water at 38 C for Ihour, and then stored at 1+1C for 37 days before ripening at 20 C. Prestorage hot water treatment enhanced ACS activity, ACC, ethylene production and respiratory rate significantly. 68.2% control tomatoes didn’ t ripen normally after cold storage, whereas 90. 0% heated tomatoes ripened normally by increasing ethylene production.3. Prestorage hot water treatment increased the activities of SOD, CAT, and APX (P<0.05) but could not raise POD, and persisted high activities of CAT and APX during long chilling storage. These results indicated prestoragehot water treatment might keep membrane permeability by improving the activities of antioxidant enzymes.4. In order to investigate the relationship between polyamines and CI, free, conjugated and bounded polyamine levels (putrescine(Put), spermidine(Spd), and spermine(Spm)) were analyzed by high-performance liquid chromatography (HPLC). The most contents of polyamine in tomato fruit was free polyamine, and the lest one was bound polyamine.In the tomato fruit stored at 1 C, free polyamine (f-PAs) level increased, conjugated polyamine (c-PAs) level stablized, and bound polyamine (b~PAs) increased in 1 month then decreased. Heat treatment increased the level of Spd and Spm and c-PAs levels. Exogenous polyamine treatment increased f-PAs , c-PAs levels, but no effect on b-PAs levels. Put and Spm treatment inhibited membrane electrolyte leakage increase and reduced CI. These results implied that the increase in Spm and Put levels in response to chilling exposure might serve as a defense mechanism against CI, and the effectiveness of Spm was more resistance to CI than that of Put. MGBG treatment increased f-PAs level, decreased c-PAs level. 0-phenanthro treatment increased c-PAs level in first few days, and then reduced c-PAs level in late days, inhibited the increase of b~PAs seriously . MGBG and 0-phenanthro aggravated membrane electrolyte leakage and CI.These results indicated that bound polyamine level was the premise factors against chilling injury, and increase in Spd, Spm and conjugated polyamine levels in response to chilling exposure might reduc chilling injury of tomato fruit. And hot water treatment might delay chilling injury and decay of tomato fruit through a mechanism that involved Spd, Spm and conjugated polyamine levels.更多还原