Effect of Lepidium perfoliatum seed gum — Oleic acid emulsion coating on osmotic dehydration and subsequent air-drying of apple cubes

The objective of this study was to investigate the effects of Lepidium perfoliatum seed gum (0, 0.5 and 1 % w/v) and oleic acid (0, 2 and 3 % v/v) coatings on the mass transfer and quality of osmotic dehydrated apple cubes. For this purpose, texture, color and microstructure of coated apple cubes were evaluated. Results showed that using Lepidium perfoliatum seed gum (LPSG) as a coating improved the properties of osmotic dehydrated apples. The value for water loss (WL)/solid gain (SG) increased when 0.5 % LPSG was used; however, at 1 % LPSG concentration, the WL/SG value decreased significantly. Apple cubes coated with 0.5 % LPSG and osmotic dehydrated for 120 min had the highest dehydration index (WL/SG). During the osmotic dehydration, coating with 0.5 % LPSG reduced the color changes and puffed structure, while it increased the hardness of the samples. Although oleic acid decreased the hardness of osmotic dehydrated apple cubes, there were no significant difference between the samples coated. The apple cubes coated with 0.5 % had the optimal mass transfer and physical properties. Therefore, this sample was then dried by hot air using three temperatures of 50, 60 and 70 °C. During hot air drying, the lowest effective diffusion coefficient, hardness, color change, shrinkage and porosity was observed for sample coated with LPSG. Dried sample at 60 °C had the minimum hardness and gumminess. By modeling the kinetics of drying the Midilli and Kucuk model was selected, since this model had the best conformity with experimental data.