壳聚糖和抗坏血酸复合处理提高台湾青枣采后保鲜效果

为了延长台湾青枣(Ziziphus mauritiana Lam.)的采后保鲜时间,基于抗坏血酸(ascorbic acid,As A)可提高果实抗氧化能力,壳聚糖涂膜处理能防止果实失水和微生物侵染,该文探讨抗坏血酸、壳聚糖涂膜及抗坏血酸和壳聚糖复合处理对台湾青枣(Ziziphus mauritiana Lam.)采后保鲜效果的影响.果实采收后当天,分别用30.0mmol/L抗坏血酸浸泡处理、8g/L壳聚糖涂膜以及30.0mmol/L抗坏血酸浸泡后并用8g/L壳聚糖涂膜复合处理,以双蒸水浸泡处理为对照,处理结束后,置于(25±1)℃和90%~95%相对湿度下贮藏,定期测定果实相关生理参数,扫描电镜观察果皮果实组织结构.结果表明,与对照相比,抗坏血酸或壳聚糖单独处理虽然对台湾青枣保鲜有一定效果,但复合处理后保鲜效果更好.表现为显著减少果实失水率和相对电导率(P<0.05),抑制果皮叶绿素降解及果实果胶酶和多聚半乳糖醛酸酶活性增加,降低原果胶分解成可溶性果胶的速率(P<0.05),使果实硬度和细胞完整性得以维持;延缓果实超氧化物歧化酶(superoxide dismutase,SOD)和过氧化氢酶(catalase,CAT)活性下降,降低膜脂氧化速率,果实过氧化氢和膜脂过氧化产物丙二醛含量显著下降(P<0.05);维持果实较高的可溶性固形物(total soluble solids,SS)、可溶性总糖(total soluble sugar,TSS)、可滴定酸(titratable acidity,TA)、谷胱甘肽(glutathione,GSH)及抗坏血酸含量.研究结果说明,抗坏血酸和壳聚糖复合处理可提高台湾青枣贮藏过程中的抗氧化能力,降低氧化伤害;降低果实失水率,减缓果皮叶绿素降解速率,延缓细胞降解和软化速率,维持果实细胞完整性,降低果实的腐烂率,从而达到延长采后果实保鲜的效果.

Improving preservation effects of Taiwan jujube fruits by using chitosan coating combined with ascorbic acid during postharvest period

In order to demonstrate the fact that ascorbic acid (As A) increased anti-oxidation and chitosan prevented dehydration and microbial attack, this paper systematically investigate effects of chitosan coating, As A, and their combinational treatment on preservation of harvested Taiwan jujube fruits during storage. In treatment of 30.0 mmol/L As A, 8 g/L chitosan, 30.0 mmol/L As A combined with 8 g/L chitosan, and dipped in deionized water (as control), respectively, all samples were stored in darkness at (25±1)℃ and 90%-95% relative humidity. Relative physiological parameters were measured and cells structures were observed by scanning electron microscope in pericarp and pulp tissue. Results showed that, compared to the control, As A or chitosan alone improved storability of harvested fruits and their combinational treatment showed a better effect. Fruits water loss and relative leakage rate of pericarp were markedly reduced (P<0.05), and an increase in pericarp chlorophyll degradation and activities of pectin methylesterases (PME) and polygalacturonases (PG) in pulp was inhibited, and degradation rate of protopectin to soluble pectin was markedly reduced (P<0.05). Thus, high degree of fruits firmness and integral cell structure was maintained. A decrease in activities of superoxide dismutase (SOD) and catalase (CAT) was alleviated, membrane oxidation rate was reduced, and thus contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were markedly decreased (P<0.05). An increase in contents of soluble sugars, total soluble solids, titratable acidity, glutathione and As A was achieved. It was indicated that chitosan coupled with As A treatment play active roles in enhancing anti-oxidation, decreasing oxidation injury, fruits water loss, and chlorophyll degradation, alleviating pericarp browning, delaying fruits softening, maintaining cell integrity, and reducing decay rate, thus realizing improved preservation effects of harvested Taiwan jujube during storage.