Foam-mat drying kinetics for acerola and adjustment of the mathematical models

Abstract Acerola (Malpighia emarginata DC) is a fruit rich in nutrients, especially vitamin C, but the in natura fruit is highly perishable and hence processing of the acerola pulp becomes indispensable. The aim of this paper was to study the foam mat drying process of acerola pulp to evaluate the effect of temperature on the drying kinetics of the pulp and fit mathematical models in order to describe the operation. The experiment was carried out with three repetitions. The foam was prepared with 250 mL of the pulp plus 4% of foaming agent and spread evenly in stainless steel trays. The selected drying air temperatures were 50 °C, 55 °C, 60 °C, 65 °C and 70 °C. The moisture ratios were then calculated and the Page, Henderson and Pabis and Lewis mathematical models fitted for each temperature. The Page model showed the highest determination coefficient (> 0.99) and lowest standard error for the regression at all temperatures (<0.03). The proposed generalized model presented a determination coefficient of 0.9933. The Page model and the generalized model were adequate to describe the drying process of the acerola pulp. The moisture contents of the dehydrated products were in accordance with the values established by Brazilian law.

针叶樱桃（Acerola，学名Malpighia emarginata DC）是一种营养富集型果实，尤其富含维生素C，但天然鲜果极易腐烂变质，因此针叶樱桃果浆的加工变得不可或缺。本研究旨在探究针叶樱桃果浆的泡沫垫干燥（foam mat drying）工艺，考察干燥温度对果浆干燥动力学的影响，并通过拟合数学模型以描述该干燥过程。实验设置三次重复：以250mL果浆添加4%发泡剂制备泡沫体系，随后将其均匀铺展于不锈钢托盘之中。本次实验选取的干燥空气温度分别为50℃、55℃、60℃、65℃与70℃。随后计算物料含水率比，并针对各温度下的干燥过程分别拟合Page模型（Page model）、亨德森-帕比斯模型（Henderson and Pabis）以及Lewis模型（Lewis model）。结果表明，Page模型在所有测试温度下均展现出最高的决定系数（>0.99）与最低的回归标准误差（<0.03）。本研究提出的广义模型决定系数达0.9933。Page模型与广义模型均可有效描述针叶樱桃果浆的干燥过程。脱水产物的含水率符合巴西法律法规所规定的限值要求。