紫果西番莲果实发育过程中挥发性香气物质及相关酶活性的变化

以西番莲香气物质较丰富的紫果‘台农1号’为试材,选取未成熟（T₁）、近成熟（T₂）和完全成熟（T₃）3个时期果实,采用顶空–固相微萃取–气质联用（HS-SPME-GC-MS）技术测定3个果实发育过程的挥发性香气物质组成及含量变化情况,同时检测对应果实中酯类香气物质合成相关的脂氧合酶（LOX）和醇酰基转移酶（AAT）活性,以期了解不同发育时期果实主要致香物质变化情况及物质与相关酶活性之间的相关性。结果表明：随着西番莲果实成熟度的增加,挥发性香气物质的种类和含量均有很大的提高,3个时期检测的香气物质总数分别为72种、95种和136种,总峰面积呈倍数增加;未成熟（T₁）和近成熟（T₂）2个时期萜烯类和酯类物质为主要的挥发性香气物质,在完全成熟（T₃）时期主要的挥发性香气为酯类,其峰面积占总峰面积达80.31%;随着果实成熟度的增加,酯类香气的种类和含量不断的提升,其中己酸乙酯,1-甲基己酯-己酸、丁酸乙酯、辛酸乙酯、1-甲基辛酯-丁酸、己酸己酯、1-甲基己酯-丁酸、丁酸己酯、(Z)-3-己烯基酯-己酸、乙酸己酯、2-甲基-辛酯-丙酸、辛酸己酯、3-羟基乙酯-己酸、(Z)-2-丁酸-乙酯等含量提升或占比较大,这些脂肪酸代谢途径产生的酯类在西番莲果实成熟过程中可能发挥了致香作用。LOX是酯类合成第一步的限速酶,AAT为酯类合成最后的关键酶。对不同发育期果实酯类合成相关酶活性测定结果表明,随着果实成熟度的增加,LOX、AAT酶活性呈上升趋势,尤其是T₃时期AAT酶活性显著的提升。由此推断,紫果西番莲果实发育过程中LOX和AAT酶的活性与酯类香气成分形成直接相关,酶活性的提升促进酯类香气的合成。

Changes of Volatile Aroma Compounds and Related Enzyme Activities During Fruit Development of Passiflora edulis

In order to understand the changes of main aroma components and the correlation between aroma components and related enzyme activities in fruits at different development stages, purple fruits ‘Tainong No.1’, which is rich in aroma components, were selected as the test material, and three stages of fruit including immature stage (T₁), near mature stage (T₂) and fully mature stage (T₃) fruits were selected. The composition and content of volatile aroma substances during the development of the three fruit stages were determined by headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the activities of lipoxygenase (LOX) and alcohol acyltransferase (AAT) related to the synthesis of ester aroma components in corresponding fruits were detected. Results showed that with the increase of fruit maturity, the types and contents of volatile aroma compounds were greatly improved. The total numbers of aroma compounds detected in three different maturity stages were 72, 95 and 136, respectively, and the total peak area increased several times. Terpenes and esters were the main volatile aroma compounds in immature (T₁) and near mature stage (T₂), while esters were the main volatile aroma compounds in full mature (T₃) stage, with the peak area accounted for 80.31% of the total peak area. Among the esters, ethyl hexanoate, 1-methylhexyl hexanoate, ethyl butyrate, ethyl octanoate, 1-methyloctyl butyrate, hexyl hexanoate, 1-methylhexyl butyrate, hexyl butyrate, (Z) - 3-hexenyl ester hexanoate, hexyl acetate, 2-methyl-octyl-propionic acid, hexyl octanoate, 3-hydroxyethyl-caproic acid, (Z) - 2-butyric acid ethyl ester increased or accounted for a large proportion. The esters which were produced by fatty acid metabolism pathway may play an aromatogenic role in the ripening process of passion fruit. LOX was the rate limiting enzyme in the first step of ester synthesis, and AAT was the key enzyme in the last step. Results showed that the activities of LOX and AAT increased with the increase of fruit maturity, especially at T₃ stage. It was concluded that the activities of enzymes were directly related to the formation of aroma components during the fruit development of Passiflora edulis, and the enhancement of enzyme activities promoted the synthesis of ester aroma.