Abstract Present work investigates the effect of thermal transitions and enthalpy relaxation phenomenon on the physico-chemical stability of paprika microencapsulated powders. Wall materials were combinations of soy protein isolates, maltodextrin and gum arabic. Powders stability was evaluated through the solid-water interactions, determined by sorption kinetics, calorimetry and color changes. The water sorption isotherms were well described by the GAB model. Below the critical condition, aw 0.6 and water content 11% (d. b.) the systems were in amorphous state at 25 °C, and enthalpy relaxations were detectable as endothermal events in the stored samples. The magnitude of the enthalpy relaxations increased with storage temperature below Tg and with time of storage. In the amorphous microencapsulates, luminosity changes measured as (Lo*-L*) values decreased as a function of time and aw, indicating pigment decoloration. The kinetics of the enthalpy relaxations changes, instead of the punctual values of the variables under study, were related to the dynamics of deteriorative changes. It can be concluded that enthalpy relaxation phenomenon can be established as a criterion for defining storage conditions or predict changes in microencapsulated and other systems that have to be stored in the glassy state.

中文翻译：

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与微胶囊化辣椒粉稳定性相关的热转变和焓弛豫

摘要 目前的工作研究了热转变和焓弛豫现象对辣椒粉微胶囊化粉末物理化学稳定性的影响。壁材料是大豆分离蛋白、麦芽糖糊精和阿拉伯树胶的组合。粉末稳定性通过固水相互作用进行评估，由吸附动力学、量热法和颜色变化确定。GAB 模型很好地描述了水吸附等温线。在临界条件下，aw 0.6 和水含量 11% (db)，系统在 25 °C 处于无定形状态，并且在存储的样品中可检测到焓弛豫作为吸热事件。焓弛豫的幅度随着低于 Tg 的储存温度和储存时间而增加。在无定形微囊中，作为 (Lo*-L*) 值测量的光度变化作为时间和 aw 的函数降低，表明色素脱色。焓弛豫变化的动力学，而不是所研究变量的准时值，与恶化变化的动力学有关。可以得出结论，焓弛豫现象可以作为定义储存条件或预测必须以玻璃态储存的微胶囊和其他系统的变化的标准。