梯度降温对鸭梨采后果肉膜脂过氧化及褐变的影响

Effect of Gradient Cooling on Membrane Lipid Peroxidation and Browning of Yali Pear Flesh after Harvest

以不同成熟度鸭梨为试材,采用每2.5d降1℃,30d降至(0±1)℃的梯度降温方法,探讨梯度降温对鸭梨果肉膜脂过氧化及褐变的影响。结果表明:鸭梨采后果肉褐变指数与丙二醛(MDA)含量、自由基含量呈显著的正相关,与还原性物质含量、保护酶活性呈显著的负相关。梯度降温提高了早采果果肉超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性,一定程度上延缓了VC、还原性谷胱甘肽(GSH)含量的下降,抑制了过氧化氢(H2O2)、超氧阴离子自由基(O2-.)的积累,降低了MDA含量和膜渗透率,从而抑制了鸭梨果肉褐变。与早采鸭梨相比,晚采鸭梨果肉中VC和GSH含量高但下降快,O2-.、H2O2和MDA积累量高,SOD和POD活性较低,梯度降温促进了晚采果果肉的膜脂过氧化和褐变。所以,适时采收结合梯度降温可以很好抑制鸭梨采后果肉褐变。

The effect of gradient cooling （storage at 12 ℃ and cooling them to （0 ±1） ℃ over 30 days at a gradual interval of 1 ℃ every 2.5 days） on membrane lipid peroxidation and browning of Yali pear flesh with different maturity was explored. The results showed that flesh-browning index had significantly positive correlation with MDA and radical content, and significantly negative correlation with reducing substance and protective enzyme. Gradient cooling improved the activities of SOD, CAT and POD, delayed the decrease of vitamin C and GSH contents to a certain extent, inhibited the accumulation of H2O2, O2-＂ free radicals, reduced MDA content and membrane permeability, and retarded flesh browning of Yali pears at the early stage after harvest. In contrast, the contents of vitamin C and GSH in the flesh of Yali pears at the late stage after harvest were obvious higher and revealed a fast decrease during storage. Meanwhile, higher contents of O2- , H2O2 and MDA, and lower activities of SOD and POD were also determined. Therefore, gradient cooling can accelerate membrane lipid peroxidation and flesh browning of Yali pears at the late stage after harvest. Timely harvesting combined with gradient cooling can efficiently inhibit the flesh browning of Yali pears during storage.