Effect of pre treatment methods on fruits drying of grapes under warm air condition
In the present study, grapes pretreated with different concentrations of potassium carbonates plus olive oil and soy lecithin with different dipping times. A dryer was built to perform the experiment under controlled condition of drying air at temperature 50°C and velocity 1.0 m/s. Grapes dipped into 1percentage olive oil plus 6percentage K2CO3 emulsion, at 50°C for 2 min. prior to drying showed shorter drying times and comparatively good quality raisin, whereas grapes dipped into 1.5percentage soy lecithin, at same conditions resulted in a total drying time slightly higher than the most effective pre treatment. The drying rates of grapes were modeled by the page equations. Grapes that are naturally dried usually darken in colour, whereas dipped grapes stay yellow-green.