Mass transfer coefficient and the characteristics of coated apples in osmotic dehydrating

In a dynamic osmotic dehydration from 0 to 180 min, the influence of different edible coating materials such as Low-Methoxyl Pectinate (LMP), Carboxyl-Methyl Cellulose (CMC), Corn Starch, and an osmotic sucrose solution with two concentration of 50% and 60% (w/w) on apple rings and their physical characteristics were studied, which included: moisture loss (ML), solid gain (SG), ML/SG ratio, effective diffusivity of solute and water (Des, Dew). The qualitative characteristics such as: firmness of the texture or shear stress (SS), and Browning index (BI) were also tested. Using Fick's first and second laws, the effective diffusion coefficient of water and solute were calculated. Osmosed apples in solution with 60% sucrose concentration, showed higher ML/SG ratio than other samples and, apples coated with 2% CMC and osmodehydrated in 60% sucrose, showed not only higher ML/SG ratio but higher diffusivity coefficient as well. The results showed that in comparison with non-coated samples, coating process can cause to improve the textural structure of the apple rings. By increasing the concentration of osmotic solutions, the Browning index (BI) of both coated and uncoated samples decreased.

Research highlights▶ Dynamic osmotic dehydration study on apple rings with different edible coating. ▶ Parametric study of moisture loss, solid gain, diffusivity, texture and browning. ▶ Comparing of edible coatings and non-coated osmodehydrated apples. ▶ Finding of optimal conditions: CMC concentration of 2% and 60% sucrose.