Shafafi Zenoozian - Department of Food Science & Technology, Shahid Beheshti University, Tehran, Iran
Poor Reza - Department of Computer Engineering, Ferdowsi University, Mashhad, Iran
Segare - Department of Computer Engineering, Ferdowsi University, Mashhad, Iran
Razavi - Department of Computer Engineering, Ferdowsi University, Mashhad, Iran

Pumpkin are traditionally dried with solar dryers or hot air dryers ,which decrease product quality .To improve the quality of dehydrated pumpkins ,the technique of osmotic dehydration followed by hot air drying has been tested in recent years.The objectives of this study were to investigate the effect of osmotic dehydration as a pretreatment before hot air drying. A computer vision system(CVS) apply to study the color changes during drying.Pumpkin cubes were soaked in 50 %w/w sorbitol and sucrose solutions at 50c for up to 6 hours followed by hot air drying at 60 c nd air velocity 1 m/s .A CVS was used for color evaluation during which the color image were converted to L/a/b values .Parameters related to shape (area, perimeter, energy) decreased during drying time. Parameters related to the texture of the image and calculated from the color co-ordinates represented well the complexity and non-homogeneity of the visual appearance of samples. The color changes of dried samples were evaluated with total color change (ΔE*),which was fitted to ΔE* = a0 +a1(t) a2. the "b" and L values were decreased,but the a values were increase in pumpkin samples during hybrid osmotic –air drying respectively.Hot air dried samples pretreated sorbitol had a higher L values compared to the hot air along drying while that pretreated with sucrose exhibited lower L values.The ΔE* values increased during drying in a sequence of ΔE* sucrose solution< ΔE* sorbitol solution< ΔE* sucrose+hot-air< ΔE* sorbitol + hot-air

Pumpkin; Image processing; Image analysis