Analysis of volatile components in Annona montana fruit at different developmental stages

XU Zijian;LONG Yali;JIANG Xuefei;QIAO Fei;DANG Zhiguo;CHEN Yeyuan;Ministry of Education Key Laboratory of Protection and Development Utilization of Tropical Crop Germplasm Resources (Hainan University)·College of Horticulture and Landscape Architecture, Hainan University;Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences ·Key Laboratory of Crop Gene Resources and Germplasm Enhancement in Southern China;

Annona montana;;Fruit development;;Volatile component;;SPME;;GC/MS

【Objective】Annona montana is native to central America, the Amazon, and the islands in the Caribbean. It is a medicinal plant and produces edible fruit. It has been used as rootstock for cultivated Annonas since 1980 s in southern China, Guangdong province and Hainan Province. The fruit is nearly round and covered with many short fleshy spines. During ripening, the pulp turns from white to yellow,and emits unique aroma. Though the pulp is fibrous and with many seeds, it is with strong tropical fruit aromas and can be used as additive to make tropical flavor food or beverage. However, volatile components in the fruit have not been identified since the wild trees of Annona montana were introduced to China. Therefore, in this study the variation and composition of volatile components in Annona montana fruit were analyzed at different fruit development stages.【Methods】Volatile components were analyzed with HS-SPME-GC/MS. Flesh of green fruit, degreening fruit and ripe fruit was sampled and quickly frozen in liquid nitrogen and then preserved in-80 ℃. 15 g of the finely powdered flesh samples was transferred into a 40 m L Teflon capvial(Thermo Fisher Scientific) with 5 g of Na Cl and sealed with a silicone/PTFE sep-tum and a magnetic cap for continuous agitation and heating. Headspace volatiles were extracted by exposing a 75-μm carboxen-polydimethylsiloxane SPME fiber(Supelco, USA) to the vial headspace. The fiber was then inserted into an ISQ GC-MS(Thermo Scientific instruments, USA) injection port and the volatiles were desorbed and performed on an HP-INNOWAX column with helium as the carrier gas at a constant flow.【Results】At different stages of fruit development, the relative contents and types of volatile components changed greatly. A total of 16 volatile components with relative content higher than 1% in all three development stages were detected, including 2 aldehydes, 9 esters, 4 alcohols and 1 acid. In green fruit, the main volatile components were trans-2-hexenal, caproaldehyde, leaf alcohol and hexyl alcohol,and the relative content of the four components reached 82.61% with trans-2-hexenal accounting for48.09%. In degreening fruit, the main volatile components included caprylic acid methyl ester, prenyl acetate, methyl decanoate, 4-penten-1-yl acetate, cineole, and α-terpineol and linalool. These 7 compounds occupied 68.85% and caprylic acid methyl ester was most abundant(35.86%). Esters increased obviously in degreening fruit compared with green fruit. In ripe fruit, the relative contents of 9 volatile components were higher than 1%. They were prenyl acetate, ethyl caprylate, caprylic acid methyl ester, 4-penten-1-yl acetate, cineole, ethyl caproate, octanoic acid, α-terpineol and ethyl caprate. Their relative content was42.76% and prenyl acetate was the highest one(9.40%), followed by ethyl caprylate(9.29%). In ripe fruit,the relative content of prenyl acetate and caprylic acid methyl ester decreased dramatically. However, cineole and α-terpineol increased when compared with degreening fruit. Moreover, there were some newly appearing volatile components such as ethyl caproate(3.06%), ethyl caprylate(9.29%), methyl decanoate(1.03%) and octanoic acid(2.74%). The representative volatile component in green fruit was aldehydes,which accounted for 6.34%. In degreening fruit, the esters raised quickly and reached 63.69%. These results show that with fruit development the types of volatile components increased and their contents varied. Scent analysis of aromatic components displayed 14 types of scent in green fruit and green scent was the highest followed by fruit scent. There were 23 types of scent in degreening fruit, and 21 types in ripe fruit. In both degreening fruit and ripe fruit, the fruit scent load was the highest, and green scent dropped dramatically. The scent load in descending order in degreening fruit was fruit scent, aliphatic scent, dairy scent, jasmine scent, rose scent, animal scent, muguet scent, green scent, orchid scent, herb scent, ice scent, edible scent, acid scent, camphor scent, conifer scent, vanilla scent, earthy scent, wood scent,smoke scent, citrus scent, spice scent, narcotic scent and solvent scent. And in ripe fruit, the order was fruit scent, green scent, aliphatic scent, dairy scent, rose scent, herb scent, jasmine scent, ice scent, animal scent, orchid scent, muguet scent, camphor scent, acid scent, edible scent, narcotic scent, solvent scent, citrus scent, conifer scent, wood scent, aroma-chem scent and spice scent.【Conclusion】During fruit development of Annona montana, the volatile components and their relative contents changed obviously. The typical volatile components were esters in both degreening fruit and ripe fruit. The types of scent increased significantly and switched from green scent to fruit scent. The degreening fruit was with the most types of scent, and the mixture of fruit scent, aliphatic scent, dairy scent, jasmine scent, rose scent, and so on. All these contributed to the special flavor of the fruit. Since degreening fruit was with stronger aromatic scent than ripe fruit, it was suggested that the degreening fruit was the best for fresh-eating and flavor compounds extraction.