热水处理对近冰温贮藏鲜枣品质提高与膜脂代谢的相关性分析

Correlation Analysis of Hot Water Treatment on Quality Improvement and Membrane Lipid Metabolism of Fresh Jujube Stored at Near Freezing Point Temperature

以采后临泽小枣(Zizyphus jujuba Mill.cv.Linzexiaozao)为实验材料,探讨热水处理对近冰温贮藏鲜枣果实耐冷性与膜脂脂肪酸组分变化的影响。采后果实用60℃热水浸泡1 min,自然干燥后,装入带有若干小孔(孔径为2 mm)的聚乙烯塑料饭盒,置于(−1.5~−2)℃的冷库中贮藏,定期测定果实冷害指数、细胞膜透性、丙二醛(MDA)、脂氧合酶(LOX)活性及膜脂脂肪酸组分变化。与对照相比,贮藏50 d时,热水处理果实的冷害指数、相对电导率、MDA和LOX活性分别降低了7.56、17.93%、17.93μmol/g·FW和15.84 U/g·FW,不饱和脂肪酸油酸(C_(18:1))、亚油酸(C_(18:2))和亚麻酸(C_(18:3))的相对含量及膜脂脂肪酸不饱和指数(IUFA)、脂肪酸不饱和度(UFA/FA)分别增加了11.10%、9.13%、8.60%和55.17、0.65,饱和脂肪酸肉豆蔻酸(C_(14:0))、棕榈酸(C_(16:0))、硬脂酸(C_(18:0))和花生酸(C_(20:0))的相对含量也分别降低了54.10%、18.66%、17.93%和3.37%,且差异显著(P<0.05)。尤其是对照LOX活性与亚麻酸(C_(18:3))的相对百分含量变化有极显著(P<0.01)的负相关性(r=−0.931)。结果表明,鲜枣在近冰温冷藏下发生冷害的程度与膜脂中亚麻酸(C_(18:3))的相对含量变化存在相关性。热水处理抑制了鲜枣膜脂脂肪酸不饱和指数(IUFA)和脂肪酸不饱和度(UFA/FA)的下降,诱导膜脂中不饱和脂肪酸的降解速率减缓,从而维持较高的膜脂稳定性,使采后鲜枣近冰温贮藏的耐冷性增强。

The effects of hot water treatment on cold tolerance and fatty acid compositions of membrane lipids of fresh jujube fruit were investigated at a near freezing point temperature storage by Zizyphus jujube Mill.cv.Linzexiaozao experimental material.The harvested fresh jujube fruits were immersed in hot-water at 60℃for 1 min,and dried naturally,then packed into polyethylene plastic boxes with several small holes about 2 mm of diameter and stored at(−1.5~−2)℃.Chilling injury index,cellular membrane permeability,malondialdehyde(MDA),lipoxygenas(LOX)activity and fatty acid constituents of membrane lipids in fresh jujube fruits during cold storage were measured at fixed periods.As compared to the control fruit,the fruit chilling injury index,cellular membrane permeability,MDA content and LOX activity decreased by 7.56,17.93%,17.93μmol/g·FW and 15.84 U/g·FW,respectively,after storage for 50 days.The relative contents of unsaturated fatty acids oleic acid(C_(18:1)),linoleic acid(C_(18:2))and linolenic acid(C_(18:3)),index of unsaturated fatty acids(IUFA)and unsaturation degree of fatty acids(UFA/FA)increased in jujube pulp by 11.10%,9.13%,8.60% and 55.17,0.65,respectively,while the relative contents of saturated fatty acids myristic acid(C_(14:0)),palmitic acid(C_(16:0)),stearic acid(C_(18:0))and arachidic acid(C_(20:0))decreased in jujube pulp by 54.10%,18.66%,17.93% and 3.37%,respectively,and the difference were significant(P<0.05).Especially,there was a very significant negative correlation(P<0.01)between LOX activity and the relative percentage content of linolenic acid(C18:3)(r=−0.931)in the control.The results showed that there was a correlation between the degree of chilling injury of fresh jujube and the relative content of linolenic acid(C_(18:3))in the membrane lipid.Hot water treatment inhibited the decrease of the index of unsaturated fatty acids and the unsaturated degree of fatty acids of fresh jujube,and induced the slowdown of the degradation rate of unsaturated fatty acids of membrane lipid,so as to maintain the high stability of membrane fat and enhance the cold tolerance of postharvest fresh jujube during near freezing point temperature storage.