Study On Variation Of Ascorbic Acid Metabolism And Volatile Substances Of Actinidia Eriantha CV.'White' Among Different Maturities During Storage

Ascorbic acid(AsA,commonly known as vitamin C)acts as an important factor for evaluating the fruit quality of kiwifruit.In this paper,Actinidia eriantha cv.'White' fruit,a rich AsA cultivar,were harvested at 155 d,165 d,or 175 d after full bloom(marked as maturity ?,? or ?).For providing more imformation about quality control of cv.'White' fruit during postharvest,changes in quality,AsA metabolism and volatile components of fruit among different maturities were investigated during storage at 23 ?.The main results were as follows:1.The maturity ? fruit were rapid deterioration of quality during storage,and were suitable to be consumed in the local region.The maturity II fruit showed a long storage life and were suggested as one appropriate harvest maturity,but the taste and nutrition of these fruit were not better as compared to maturity I fruit.The maturity I fruit showed significantly higher contents of nutrients including phenols,organic acids and AsA(the contents of total phenol and AsA were maintained over 142.52 ?g·g-1 FW and 789.66 mg·100 g-1 FW,respectively),better taste,and longer storage life,as compared to maturity ? and ? fruit Thus,maturity I was considered as the best maturity for harvesting Actinidia eriantha cv.'White' fruit.2.AsA content in 'White' fruit among the three different maturities variated during postharvest,which mainly attributed to the differences in capabilty of AsA biosynthesis and regeneration metabolism among these fruit.AsA accumulation in maturity I fruit was associated with AsA biosynthesis and regeneration,and the key enzymes involed in the metabolic pathway were Ga1DH and DHAR.During storage,AsA content in the maturity ? fruit maintained a relatively steady level,while the content in maturity ? fruit accumulated,which mainly attributed to AsA regeneration.However,the key enzyme of AsA metabolic pathway of the former was MDHAR,and the latter was DHAR.3.A total of 41,33,and 36 kinds of volatile components were found in maturity I,II and III fruit,respectively.Aldehydes and ketones were the main volatile components in 'White' fruit throughout storage,among which 2-hexenal was accounted for the largest proportion.During storage,'White,fruit could inhibit the accumulation of undesirable flavor by maintaining higher relative contents of aldehydes and ketones,and lower relative contents of alcohols and esters(16%or less).During storage,there was variation in the volatile substances in fruit among different maturities.The maturity III fruit contained more kinds of aldehydes and ketones,and higher relative contents of esters and alcohols.The maturity II fruit contained higher relative contents of aldehydes,ketones,ethers and hydrocarbons.The maturity I fruit maintained richer volatile com-ponents(41 kinds)and higher relative contents of esters,aldehydes,ketones and alcohols during storage,and presented better flavor quality than the maturity ? and ? fruit.