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

【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.