柿脱涩过程中褐变及相关酶活性的变化规律

Browning and related enzyme activities in de-astringent treatment of persimmon

【目的】研究涩柿果实CO_(2)脱涩过程中的褐变现象,了解褐变相关生理生化指标及酶活性的变化规律,为扩大CO_(2)脱涩技术的适用范围、提高涩柿产业经济效益提供理论支持。【方法】以极易褐变品种‘中柿1号’为试材,采用CO_(2)脱涩法对商熟期果实进行脱涩处理,根据褐变面积分为T1(25%~49%)、T2(50%~75%)和T3(≥75%)3个褐变等级,以未处理果实为对照(CK),对不同褐变等级柿果生理生化指标及褐变相关酶活性变化规律进行研究。【结果】随着褐变程度加重,‘中柿1号’果实硬度、L^(*)、a^(*)、b^(*)、可溶性单宁和总酚含量逐渐下降,MDA和不溶性单宁含量呈上升趋势,总黄酮和抗坏血酸含量及SOD、POD、CAT和PPO活性均呈先上升后下降的变化规律。相关性分析表明,可溶性单宁与不溶性单宁含量呈显著负相关关系,果实硬度、L^(*)和b^(*)值均与可溶性单宁含量呈显著正相关关系,a^(*)值与总酚含量呈显著正相关关系,抗坏血酸含量与POD、CAT活性呈显著正相关关系。【结论】用CO_(2)脱涩法处理柿果实时,高CO_(2)低O_(2)环境破坏了柿果实内部氧化还原的平衡状态,导致果实褐变。

【Objective】This study investigated the browning phenomenon in the process of CO_(2)deastringency treatment of persimmon fruit and examined physiological and biochemical indexes and enzyme activities related to the browning process to facilitate the development of persimmon fruit industry.【Method】The persimmon cultivar‘Zhongshi No.1’,susceptible to browning during CO_(2)deastringency treatment,was harvested at the commercial maturity stage for deastringency treatment.The treated fruit was divided into three grades of T1(25%-49%),T2(50%-75%)and T3(≥75%)according to browning area.Then,the physiological and biochemical indexes as well as SOD,POD,CAT and PPO activities were measured using untreated fruit as the control(CK).【Result】With the increase of‘Zhongshi No.1’browning degree,the fruit firmness,L^(*),a^(*),b^(*),soluble tannin and total polyphenols content decreased gradually,MDA and insoluble tannin showed an upward trend,while contents of flavonoids and ascorbic acid and activities of SOD,POD,CAT and PPO presented a up and down trend.Correlation analysis showed that soluble tannin had significantly negative correlation with insoluble tannin,fruit firmness,L^(*),and b^(*)values had significantly positive correlation with soluble tannin content,a^(*)value had significantly positive correlation with total polyphenol contents,while ascorbic acid,POD and CAT had significantly positive correlation with each other.【Conclusion】The balance of redox reaction was destroyed by high-CO_(2)/hypoxic condition of CO_(2)deastringency treatment and caused the browning of persimmon fruit.