Effects of glycine betaine on the postharvest quality and cell wall metabolism of <i>Malus domestica</i> fruit

Quality decline resulting from senescence and fungal invasion is a crucial factor that impacts the economic value of fruit. The present study aimed to reveal the impacts of 10 mmol L−1 glycine betaine immersion for 10 min on cell wall degradation in ‘Qiujin’ apples during storage at ambient condition for 15 d. The results showed that glycine betaine exhibited higher levels of soluble solids content, flesh firmness, and water-insoluble pectin, while also delaying the increase in mass loss, total colouration difference, and water-soluble pectin content. Furthermore, glycine betaine effectively restrained the enzymatic activities and gene expressions of pectate lyase, pectin methylesterase, polygalacturonase, cellulase, β-galactosidase, and β-glucosidase, thereby inhibiting the reduction in water-insoluble pectin content and the formation of water-soluble pectin. These findings suggest that glycine betaine can preserve the postharvest quality of ‘Qiujin’ apples by suppressing the activity and gene expression of key enzymes involved in cell wall metabolism, as well as reducing respiratory rate and ethylene release. In conclusion, the utilisation of glycine betaine treatment may present an effective technique for alleviating softening in postharvest apples and can serve as a promising natural alternative to synthetic chemicals.衰老与真菌侵染引发的品质劣变，是影响果品经济价值的关键因素。本研究旨在探究10 mmol·L⁻¹甘氨酸甜菜碱（glycine betaine）浸果10分钟，对‘秋金’苹果在常温贮藏15天过程中细胞壁降解的影响。结果表明，甘氨酸甜菜碱处理可维持更高的可溶性固形物含量、果肉硬度与水不溶性果胶水平，同时延缓质量损失率、总色差及水溶性果胶含量的上升。此外，甘氨酸甜菜碱可有效抑制果胶酸裂解酶、果胶甲酯酶、多聚半乳糖醛酸酶、纤维素酶、β-半乳糖苷酶及β-葡萄糖苷酶的酶活性与基因表达，从而阻碍水不溶性果胶含量的下降与水溶性果胶的生成。上述研究结果表明，甘氨酸甜菜碱可通过抑制细胞壁代谢关键酶的活性与基因表达，同时降低呼吸速率与乙烯释放量，维持‘秋金’苹果的采后品质。综上，甘氨酸甜菜碱处理可作为缓解采后苹果软化的有效手段，亦是一类颇具应用前景的合成化学药剂天然替代方案。