Bui Huu-Thuan, Makhlouf Joseph, Ratti Cristina
Inst. of Nutraceuticals and Functional Foods, Université Laval, Québec, QC, Canada.
J Food Sci. 2009 Jun;74(5):E250-8. doi: 10.1111/j.1750-3841.2009.01177.x.
Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 degrees Brix and at 35, 45, and 55 degrees C. Other experiments were done in a 70 degrees Brix sucrose solution at 35 degrees C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and degrees Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh(s) = 1.3 Re(0.5)Sc(s) (0.15) and Sh(w) = 0.11 Re(0.5)Sc(w) (0.5), respectively. The effective diffusion coefficients of water (4.97 10(-11)- 2.10 10(-10) m(2)/s) and sucrose (3.18 10(-11)- 1.69 10(-10) m(2)/s) depended only on temperature through an Arrhenius-type relationship.
采用包含收缩、界面处对流阻力以及水的总体流动的经典菲克定律对番茄的渗透脱水过程进行建模。将厚度为8毫米的番茄片置于浓度为50、60和70°Bx的蔗糖溶液中，在35、45和55℃下进行渗透脱水。其他实验在35℃的70°Bx蔗糖溶液中进行，使用厚度为4、6和8毫米的番茄片，并设置不同的运动水平（速度分别为0、0.053和0.107米/秒）。测量产品的番茄重量、水分含量和°Bx值随加工时间（20、40、80、160和320分钟）的变化。结果表明，温度、浓度、厚度和溶液运动对番茄渗透脱水过程中的水分损失和蔗糖吸收有显著影响。该模型预测的可溶性固形物含量和水分含量随时间的变化与实验数据高度吻合。确定了蔗糖和水的实验舍伍德数关联式分别为Sh(s)=1.3Re(0.5)Sc(s)(0.1)和Sh(w)=0.11Re(0.5)Sc(w)(0.5)。水（4.97×10⁻¹¹ - 2.10×10⁻¹⁰米²/秒）和蔗糖（3.18×10⁻¹¹ - 1.69×10⁻¹⁰米²/秒）的有效扩散系数仅通过阿伦尼乌斯型关系依赖于温度。
