Papaya fruit, widely consumed around the world, is mechanically and structurally affected by several enzymatic processes during ripening, where pectin methylesterase plays a key role. Hence, the aim of this work was to evaluate possible correlations among physicochemical changes, mechanical parameters, viscoelastic behavior, and enzyme activity of pectin methylesterase to provide information about the softening phenomenon by applying the Maxwell and Peleg models. Mechanical parameters were estimated by texture profile analysis, enzyme activity by Michaelis-Menten parameters, and viscoelastic behavior by relaxation test responses fitted to these models. The Maxwell model described properly mechanical changes during ripening, displaying a better adjustment (R2 > 0.97) than the Peleg model (0.80 < R2 < 0.84). Pearson correlation analysis (P ≤ 0.01) indicated an inversely proportional relation among firmness, total soluble solids, and the first elastic element of the Maxwell model. Besides, the PME Michaelis-Menten affinity constant showed a correlation between the first elastic element and the first viscoelastic element of the Maxwell model. Findings of this work pointed out that the first Maxwell elastic element could explain structural changes as papaya ripening advance, associated with pectin methylesterase activity, cell wall disruption, and cell assembling into the tissue. PRACTICAL APPLICATION: Mechanical and viscoelastic behavior of papaya fruit tissue were described by the Maxwell model associating both viscous and elastic elements to the softening process. The results provide background and practical knowledge to describe structural changes during the ripening process of papaya depending on its enzymatic activity. Outcomes could be further applied to understand changes in other fruits or food matrixes that soften during postharvest, storage, and food chain supply processes.

中文翻译：

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番木瓜可食组织成熟过程中 PME 活性、粘弹性和结构参数的相关性

在世界各地广泛消费的木瓜果实在成熟过程中受到多种酶促过程的机械和结构影响，其中果胶甲酯酶起着关键作用。因此，这项工作的目的是评估果胶甲酯酶的物理化学变化、机械参数、粘弹性行为和酶活性之间可能的相关性，以通过应用 Maxwell 和 Peleg 模型提供有关软化现象的信息。机械参数通过质地分布分析、酶活性通过 Michaelis-Menten 参数估算，粘弹性行为通过拟合这些模型的松弛测试响应估算。Maxwell 模型正确地描述了成熟过程中的机械变化，显示出比 Peleg 模型（0.80 < R2 < 0.84）更好的调整（R2 > 0.97）。Pearson 相关分析 (P ≤ 0.01) 表明硬度、总可溶性固体和 Maxwell 模型的第一弹性元素之间成反比关系。此外，PME Michaelis-Menten 亲和常数显示了 Maxwell 模型的第一弹性元件和第一粘弹性元件之间的相关性。这项工作的结果指出，第一个麦克斯韦弹性元件可以解释木瓜成熟过程中的结构变化，与果胶甲酯酶活性、细胞壁破坏和细胞组装成组织有关。实际应用：木瓜果实组织的机械和粘弹性行为由麦克斯韦模型描述，该模型将粘性和弹性元素与软化过程相关联。结果为描述木瓜成熟过程中取决于其酶活性的结构变化提供了背景和实践知识。结果可以进一步应用于了解在收获后、储存和食物链供应过程中软化的其他水果或食物基质的变化。