黑莓渗糖过程中水分和溶质扩散的数学模型

Mathematical model of water and solute diffusion in blackberry during sugar osmotic dehydration process

以黑莓-白糖固液体系为研究对象,研究了黑莓在不同条件糖溶液中的渗透脱水规律,得出了渗糖过程中水分和溶质扩散的数学模型。渗透液的质量分数选取40%、50%、60%,溶液的温度选取30、40、50℃,糖溶液和黑莓的质量比为10∶1,渗透脱水时间为0~5 h。利用AZUARA等提出的双组分系统数学模型得到了每种实验条件下黑莓样品最终渗透平衡状态时的失水率和固形物增加率,结果表明,在一定实验条件范围内,黑莓脱水率和固形物增加率均随渗透液浓度、渗透时间和溶液温度的增大而增大;同时使用菲克第二定律估算了每种试验条件下水分和糖的有效扩散系数,上述渗透条件下水分和糖的有效扩散系数分别在1.77×10^(-9)~2.10×10^(-9)m^2/s和1.36×10^(-9)~1.60×10^(-9)m^2/s范围内。

In this study,mass transfer during osmotic dehydration of blackberry in sugar solution was investigated. The osmotic solution concentrations were 40%,50% and 60%(w/w) of sugar,osmotic solution temperatures were 30 ℃,40 ℃ and 50 ℃,the solution-to-blackberry mass ratio was 10 ∶ 1(w/w) and the process duration varied from 0 to 5 hr. A two-parameter mathematical model developed by Azuara et al. was used for describing the mass transfer and estimating the final equilibrium water loss and solid gain. The results showed that the dehydration rate and solid gain rate of blackberry were increased with the increase of osmotic concentration,osmotic time and temperature under certain conditions. Effective diffusivity of moisture as well as solute was estimated by Fick's second law of diffusion. For above conditions of osmotic dehydration,water and sugar effective diffusivities were in the range of 1. 77 × 10^(-9)-2. 10 × 10^(-9) and 1. 36 × 10^(-9)-1. 60 × 10^(-9) m^2/s,respectively.