外源抗坏血酸处理对人工脱涩柿果的保鲜作用

Effects of exogenous ascorbic acid treatment on persimmon fruit freshness after de-astringency

关键词:  柿, 贮藏, 抗坏血酸, 保鲜, 品质

Key words:  persimmon, storage, ascorbic acid, freshness, quality

摘要:

该研究以广西中部地区的早熟品种‘牛心柿'(Diospyros kaki cv. Niuxin)的果实为材料,研究果实萼片施用5%抗坏血酸溶液处理对CO₂脱涩柿果采后贮藏期果实软化和细胞壁降解以及抗氧化体系等相关生理生化指标的影响。结果表明:抗坏血酸对人工脱涩后‘牛心柿'果实的保鲜效果明显,与空白和去离子水对照相比,外源抗坏血酸处理更好地延缓柿果实硬度的降低和总色差的升高。抗坏血酸处理后7～15 d,原果胶的下降速率和可溶性果胶的上升速率得以延缓,细胞壁降解酶PG和Cx活性均低于空白和对照。同时,外源抗坏血酸阻滞了整个贮藏期果实内源抗坏血酸的减少,并抑制了POD的活性和MDA的积累,果实自身抗氧化体系功能受到保护。此外,抗坏血酸处理还在一定程度上提高了果实还原糖的含量。因此,采后外源施用抗坏血酸不仅可以延长脱涩后鲜食柿果的货架期,而且还有助于提高果实的商品品质。

Abstract:

Most persimmon fruit are of the astringent type, due to their richness in soluble tannin at maturity. Astringent persimmons need an artificial de-astringency treatment to become edible. Several of the common treatments, high CO₂, alcohol, warm water, and ethylene all cause rapid fruit softening problems. Hence, keeping fruit freshness after de-astringency is critical in the persimmon post-harvest industry, and efficient fresh keeping methods are in urgent need for this area. The present study aimed to clarify the effect of exogenous ascorbic acid(AsA)treatment on persimmon fruit softening, cell wall degradation, and antioxidant system changes after CO₂ de-astringency, in order to develop the me-thods extending persimmon shelf-life. Persimmon(Diospyros kaki cv. Niuxin)fruit harvested from middle part of Guangxi Zhuang Autonomous Region with routine CO₂ astringency removal treatment was taken as experimental material, after treating fruit sepal with five percent AsA solution, changes of physiologic and biochemical indexes related to persimmon fruit softening, cell wall degradation, and antioxidant system were studied. The results showed that AsA treatment maximized ‘Niuxin' Persimmon freshness. Exogenous AsA treatment produced higher firmness and lower total chromatism than either a blank or a control similarly treated with deionized water. From the seventh(7th)to the fifteenth(15th)days after treatment, AsA treatment delayed fruit protopectin decreasing rate and soluble pectin increasing rate, and treated fruit showed lower activity of cell wall degrading enzyme polygalacturonase(PG)and cellulase(Cx)than both of blank and control. During the whole storage period, the exogenous AsA treatment impeded the decrease of fruit endogenous AsA level, as well as better controlled peroxidase(POD)activity and malondialdehyde(MDA)accumulation, and the function of fruit antioxidant system was well protected. Additionally, the AsA treatment also enhanced reducing sugar content to a certain extent. Finally, the supplement post-harvest AsA treatment extends persimmon shelf-life after de-astringency and improves fruit commodity quality. The present work proposes to explain the physiological mechanisms of the fruit softening regulation by exogenous AsA treatment, provides basal knowledge and evidence for development of new post-harvest technologies, as well as offer guidelines to improving persimmon storability for the purpose of maintaining fruit quality in persimmon industry.