基于广泛靶向代谢组学分析白木通果肉不同成熟期的香气变化

Odor change of Akebia trifoliata ssp. australis pulp at different ripening stages based on widely targeted metabolomics

  • 摘要:目的】研究白木通果肉成熟过程中香气物质的变化规律,为白木通果实品质调控及香气物质开发利用提供参考依据。【方法】以白木通品种野牧童Ⅰ号果实硬熟期(Y0)、软化期(R0)、开裂期(K0)和后熟期(Y3)的果肉为试验材料,进行广泛靶向代谢组学和代谢物相对香气活性值(ROAV)分析,并基于差异挥发性代谢物进行KEGG代谢通路富集和感官风味分析。【结果】野牧童Ⅰ号4个时期果肉中共检测到448种挥发性代谢物,以萜类和杂环化合物的种类最多。Y0→R0→K0的整个树熟过程中,差异挥发性代谢物以上调为主,在Y0→Y3室温放熟过程中,差异挥发性代谢物以下调为主。Y0 vs R0差异挥发性代谢物富集显著的代谢通路为辅因子的生物合成(P<0.05,下同),Y0 vs K0和Y0 vs Y3中差异显著的代谢通路均为倍半萜和三萜生物合成,其次是辅因子的生物合成。4个时期果肉中鉴定出70种ROAV>1的关键香气成分,其中苯甲硫醇、3,6-壬二烯醛、5-乙基-3-羟基-4-甲基-2(5H)-呋喃酮、异戊酸苯乙酯等物质对野牧童Ⅰ号果肉香气的形成有重大影响。ROAV分析结果表明,果肉各成熟期的香味特征较为一致,甜香型占主要比重,贡献率为84.40%~89.89%,其次是辛香型和花香型,贡献率分别为2.89%~5.02%和2.71%~3.35%。果香和青香为各比较组中差异挥发性代谢物所注释到的共同感官风味特征。【结论】野牧童Ⅰ号果肉覆盖了青香、果香、甜香等多种香型,形成了其甘甜清润、鲜甜滑嫩、果香浓郁又带有淡淡椰子香的特殊风味。在树熟和采摘后室温放熟2个成熟过程中,果肉的整体香气变化较小,可将软化期采摘的果实作鲜食或短距离运输,硬熟期的果实作贮藏或长途运输。

     

    Abstract:Objective】This study aimed to investigate change patterns of aroma substances of Akebia trifoliata ssp. australis pulp during ripening, providing reference for fruit quality regulation and development and utilization of aroma substances of Akebia trifoliata ssp. australis.【Method】Fruits at hard ripening (Y0), softening (R0), cracking (K0), and ripening (Y3) stages of the variety Yemutong Ⅰ of Akebia trifoliata ssp. australis were taken as test materials. Widely targeted metabolomic analysis and relative odor activity value (ROAV) analysis were performed, and KEGG metabolic pathway enrichment and sensory flavor were analyzed based on differential volatile metabolites.【Result】A total of 448 volatile metabolites were detected in pulp of Yemutong Ⅰ at the four stages, with terpenoids and heterocyclic compounds being the most abundant. During the whole tree ripening process of Y0→R0→K0, the differential volatile metabolites were mainly up-regulated; the differential volatile metabolites were mainly down-regulated during the process of Y0→Y3 at room temperature. In Y0 vs R0, the significantly enriched pathway of differential volatile metabolites was biosynthesis of cofactor (P<0.05, the same below), while in Y0 vs K0 and Y0 vs Y3, the significantly different metabolic pathway was sesquiterpenoid and triterpenoid biosynthesis, followed by biosynthesis of cofactor. A total of 70 key odor components with ROAV > 1 were identified, among which benzyl mercaptan, 3,6-nonadienal, 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone, phenylethyl isovalerate, and other substances showed great influence on shaping pulp odor of Yemutong Ⅰ. ROAV analysis results showed that the odor characteristics of pulp at each ripening stage were relatively consistent: sweet odor type was dominant, with a contribution rate of 84.40%-89.89%, followed by spicy and floral odor types, with contribution rates of 2.89%-5.02% and 2.71%-3.35% respectively. Fruity and green odor types were the common sensory flavor characteristics annotated to the differential volatile metabolites across all comparison groups.【Conclusion】Pulp of Yemutong Ⅰ exhibits a complex odor type covering green, fruity, and sweet odors, forming a distinctive flavor characteri-zed by sweet and refreshing, tender and smooth, with rich fruity odor and a subtle hint of coconut substances. During the two ripening processes of tree-ripening and post-harvest ripening at room temperature, the overall pulp odor exhibits relatively minor changes. Therefore, fruits harvested at the softening stage are suitable for fresh consumption or short distance transportation, while those at the hard-ripening stage are more appropriate for storage and long distance transportation.

     

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