Influence of Sulphite on the Drying Kinetics of Pumpkin Fruit Slices

Abstract

80°C at an air velocity of 1.53 m/s. Drying was carried out to constant moisture. Samples were screened using descriptive sensory evaluation to obtain samples P1, 4 and P2, 5 each dried at 75°C as the best samples for 4 mm and 5 mm respectively. Drying curves, moisture diffusitivity, activation energy, drying time and rehydration capacity were determined. The drying curves obtained showed results for a short constant rate followed by a falling rate period. The effective moisture diffusivity varied from 6.235×10-11 to 12.808×10-11 m 2 /s for the 4 mm and 9.046 x 10-11 to 21.330 x 10-11 m 2 /s for the 5 mm samples. Activation energy obtained for P0, 4; P1, 4; P0, 5 and P2, 5 were 31.342, 32.292, 31.525 and 29.88 kJ/mol. respectively. Sulphiting reduced drying time at 1% level from 16.5 to 15.2 hours for the 4 mm sample and 17.8 to 16.9 hours at 2% level of sulphiting for the 5 mm. Sulphite treatment reduced rehydration capacity significantly at p>0.05. This study implies that the parameter which governed the internal transfer of moisture was moisture diffusion.