3种石榴果皮褐变与活性氧及膜脂代谢关系分析

Analysis of Browning and Reactive Oxygen Species and Membrane Lipid Metabolism in Husk of Three Pomegranate Cultivars

石榴冷藏过程中果皮易发生褐变,使贮藏品质下降。不同品种的石榴耐贮性不同。本文以“突尼斯软籽”“净皮甜”和“骊山红”3种石榴作为原材料,探究其在(4±0.5)℃,相对湿度85%~90%贮藏条件下的果皮活性氧代谢、膜脂代谢相关指标变化及差异,并分析上述指标与褐变之间的关系。结果表明:随着贮藏时间的变化,褐变指数升高,“突尼斯软籽”石榴果皮维持较低的褐变指数,贮藏第90天仅达到1.25,而“净皮甜”果皮褐变指数高达3.85;果皮的O_(2)^(·-)和·OH清除率下降,其中“净皮甜”和“骊山红”果皮的·OH清除率在贮藏第90天为0.97%和4.12%;活性氧水平提高,“突尼斯软籽”石榴果皮O_(2)^(·-)生成速率在贮藏结束时为25.31μmol/min·g;超氧化物歧化酶(SOD)活性降低,过氧化物酶(CAT)活性变化不明显;内源性抗氧化物质还原型谷胱甘肽(GSH)、类胡萝卜素、叶绿素等含量显著减少,贮藏第60天后,突尼斯软籽石榴GSH含量维持在252.9~273.7μmol/g,高于其余2个品种,“骊山红”石榴果皮ASA含量在108.0~121.8μg/g之间,处于最高水平。3种石榴果皮的细胞膜透率增加,丙二醛(MDA)不断累积,可溶性蛋白含量变化不明显。相关性分析结果显示石榴果皮褐变与活性氧代谢中O_(2)^(·-)和·OH的清除率、过氧化氢含量、SOD活性、还原型谷胱甘肽和叶绿素含量呈负相关关系,与O_(2)^(·-)生成速率呈正相关关系;与膜脂代谢中细胞膜透率和丙二醛含量呈正相关关系。主成分分析结果证实石榴果皮褐变与活性氧代谢及膜脂代谢密切相关,且“突尼斯软籽”石榴的贮藏品质与“净皮甜”和“骊山红”存在明显区别。

Pomegranate(Punica granatum L.)husk is prone to browning which would decrease the storage quality during cold storage.Different pomegranate cultivars have different storability.In the present study,three pomegranate cultivars(‘Tunisia soft seed’,‘Jingpitian’and‘Lishanhong)were used as raw material to explore the relation between husk browning and active oxygen species and membrane lipid metabolism,and further to compare the differences among three cultivars.The results showed that the browning index increased during storage time.The browning index of‘Tunisia soft seed’husk was relatively lower,reaching 1.25 on the 90th day of storage,while the browning index of‘Jingpitian’husk was as high as 3.85.The scavenging rates of O_(2)^(·-)and·OH radicals of three pomegranate husks decreased.The scavenging rates of·OH radicals of‘Jingpitian’and‘Lishan red’husk s were 0.97%and 4.12%on the 90th day of storage.The O_(2)^(·-)generation rate of‘Tunisia soft seed’pomegranate husk was 25.31μmol/min·g at the end of storage.The activity of superoxide dismutase(SOD)decreased,and the activity of peroxidase(CAT)did not change significantly.The contents of endogenous antioxidant substances such as glutathione(GSH),carotenoids and chlorophyll were significantly reduced.After 60 days of storage,the GSH content of‘Tunisia soft seed’pomegranate was maintained at 252.9-273.7μmol/g,which was higher than that of the other two cultivars.The content of ASA in‘Lishanhong’pomegranate husk was between 108.0-121.8μg/g,which was at the highest level.Cell membrane permeability of three pomegranate husks increased,malondialdehyde(MDA)accumulated,and soluble protein content did not change significantly.The results of correlation analysis showed that the browning of pomegranate husk was negatively correlated with O_(2)^(·-)and·OH free radical scavenging rate,hydrogen peroxide content,SOD activity,glutathione content and chlorophyll content of active oxygen metabolism and positively correlated with the O_(2)^(·-)production rate;positively correlated with tissue electrolyte leakage and malondialdehyde content of membrane lipid metabolism.Additionally,the results of principal component analysis further confirmed that the browning of pomegranate husk was closely related to the metabolism of reactive oxygen species and membrane lipid,and the storage quality of‘Tunisia soft seed’pomegranate was obviously different from those of‘Jingpitian’and‘Lishanhong’.