Abstract

The accumulation of solutes on the food surface has resulted in notable contradictions between data resulting from modeling and information observed experimentally. Hence, the mechanisms involved in the transport of solutes in the plant tissue during osmotic dehydration (OD) have not been well documented. The purpose of this study was to analyze solute concentration at different depths of osmotically dehydrated apple cylinder with the use of a conventional (sucrose) and a non-conventional (stevia) osmotic agent. Solute concentration was modeled by Fick's law in order to identify the thicknesses within the tissue where the solute is transferred under a diffusive mechanism. Samples were dehydrated in sucrose (30 and 50°Brix) and stevia (3 and 6% w/w) aqueous solutions. Samples were cut in five slices (${\delta }_{\mathit{cut}}=\mathrm{ }$0.5, 2, 4, 7, 10 mm in z direction) from the surface to the food center. Sample properties such as: water loss, solute gain, moisture content, solute concentration and effective diffusivity coefficients at different tissue depths and time periods of dehydration process were determined. Results showed the concentration of solutes was higher in the surface than the center for both osmotic solutions: stevia and sucrose. Fick model did not allow an adequate description of the experimental data in the area of solutes accumulation, suggesting that transfer of solutes on the tissue surface is governed by other transport mechanism different from diffusion. This result opens new ways for future research of the solutes transport within plant tissue. Under this approach, the surperficial impregnation of solutes at the surface and a diffusive phenomenon inside the sample center could be considered.

摘要

食物表面溶质的积累导致建模产生的数据与实验观察到的信息之间存在显着矛盾。因此，渗透脱水 (OD) 过程中植物组织中溶质运输的机制尚未得到充分证明。本研究的目的是使用常规（蔗糖）和非常规（甜菊糖）渗透剂分析渗透脱水苹果圆柱体不同深度的溶质浓度。溶质浓度由菲克定律建模，以确定组织内溶质在扩散机制下转移的厚度。样品在蔗糖（30 和 50°Brix）和甜菊（3% 和 6% w/w）水溶液中脱水。样品被切成五片（${\delta }_{\mathit{切}}=\mathrm{ }$0.5、2、4、7、10 毫米在z方向）从表面到食物中心。确定了不同组织深度和脱水过程时间段下的样品特性，例如：失水、溶质增加、水分含量、溶质浓度和有效扩散系数。结果表明，对于两种渗透性溶液：甜菊糖和蔗糖，表面的溶质浓度高于中心。Fick 模型无法充分描述溶质积累领域的实验数据，这表明组织表面上的溶质转移受不同于扩散的其他运输机制控制。这一结果为未来研究植物组织内的溶质运输开辟了新途径。在这种方法下，