摘要:
柑橘果皮表面覆蓋著一層蠟質,具有多重重要的生理功能.以溫州蜜柑(Citrus unshiu Marc.)和冰糖橙(Citrus sinensis Osbeck)果實為原料,采用氣相色譜-質譜聯(lián)用(gas chromatography-mass spectrometry,GC-MS)對2 種類型柑橘果皮角質層組分進行定性和定量分析,并采用掃描電子顯微鏡對其微觀結構進行觀察.GC-MS分析表明,溫州蜜柑和冰糖橙外蠟含量分別為3.7 μg/cm2和2.2 μg/cm2,內(nèi)蠟含量分別為13.9 μg/cm2和18.4 μg/cm2.溫州蜜柑和冰糖橙的外、內(nèi)蠟中脂肪族物質主要成分相同,分別為烷烴、脂肪酸、伯醇,但品種間各組分比例及碳原子數(shù)分布存在差異.角鯊烯為冰糖橙果實外蠟結構特有組分.此外,三萜類物質僅在內(nèi)蠟中檢測出.溫州蜜柑和冰糖橙的角質膜層含量分別為44.00 μg/cm2和70.00 μg/cm2,二者含量差異顯著(P<0.05).掃描電子顯微鏡結果顯示溫州蜜柑的外蠟晶體呈不規(guī)則血小板狀,冰糖橙的外蠟晶體呈倒伏的血小板狀.除去外蠟導致溫州蜜柑和冰糖橙的水分損失速率顯著增加(P<0.05).相對于脂肪酸,烷烴在保水方面具有更重要的作用.兩種類型柑橘的角質層組分及微觀結構的差異可能促成了果實采后不同的貯藏特性,這為提高不同品種柑橘耐貯性提供了重要依據(jù).%The surface of citrus peel is covered with a layer of wax, exerting multiple important physiological functions. The qualitative and quantitative analysis of cuticular components in the fruit peel of Satsuma mandarin(Citrus unshiu Marc.) and Bingtang sweet orange(Citrus sinensis Osbeck)were carried out by gas chromatography-mass spectrometry(GC-MS). Scanning electron microscopy (SEM) was used to observe the difference in the cuticle microstructure of Satsuma mandarin and Bingtang sweet orange. GC-MS results showed that the epicuticular wax contents of Satsuma mandarin and Bingtang sweet orange were 3.7 and 2.2 μg/cm2, respectively, and the intracuticular wax contents were 13.9 and 18.4 μg/cm2, respectively. The major aliphatic components of epicuticular and intracuticular wax in two citrus cultivars were identical, including alkanes, fatty acids, and primary alcohols, but their proportions and carbon number distribution were dependent on cultivars. Farnesol was found to be exclusively present in the epicuticular wax of Bingtang sweet orange. Moreover, triterpenoid compounds were detected only in the intracuticular wax. The cutin contents of Satsuma mandarin and Bingtang sweet orange were 44.00 and 70.00 μg/cm2, respectively, being significantly different. SEM showed irregular platelet flattened platelet waxes to be deposited on the surface of Satsuma mandarin and Bingtang sweet orange, respectively.The removal of epicuticular wax could cause a significant increase of water loss rate in Satsuma mandarin and Bingtang sweet orange (P < 0.05). Compared with fatty acids, alkanes played a more significant role in water retention in fruits. The differences in the chemical composition and microstructure of cuticle between citrus varieties may contribute to the differences in postharvest storage characteristics, which will provide important evidence for improving the storage quality of different citrus varieties.