Osmo-convective Drying Kinetics of Pineapple Cubes and their Quality Evaluation

Osmotic dehydration kinetics of pineapple cubes (10 mm 10 mm 10 mm) was studied over a range of sugar concentration (40, 50 and 60 0 B) and soaking temperature (30, 45 and 60 o C) of osmotic solution.The cubes were further dehydrated by convective hot air drying at 40, 50 and 60 o C. Osmotic dehydration kinetics indicated that both water loss and solids gain increased with increase of syrup soaking temperature and concentration, the former having much more effect for the range of values tested.After the osmotic treatment, the moisture content of fruits and vegetable are usually reduced by 316.24-399.54(%db).The effect of drying conditions (air temperature) on the osmo-convective dehydrated pineapple cubes on of dried product quality (TSS, pH, acidity, reducing sugar, non-reducing sugar, total sugar) was also evaluated.The drying took place in the falling rate period.The drying rate decreases with the decreases in the moisture content and it reaches to zero at the final moisture content of the osmo-convective dried of pineapple cubes.The Hendersons and Pabis Model was well fitted to the experimental data r 2 0.753.The effective diffusion coefficients for water and solute diffusion were determined, considering pineapple as slab thickness 1 cm.The effective diffusion coefficients for water as well as solute were empirically correlated with sugar concentration, soaking temperature and convective hot air temperature.The effective diffusivity was found to be in the range of 6.301 10 -8 to 3.4635 10 -7 m 2 /s.The activation energy for pineapple cubes, which was estimated by using Arrehenius equation was be in the range 220.39 to 278.84 kJ/mole.Overall score of sensory characteristics ranged from 6.3 to 8.7 for all drying temperature.The quality characteristics of dried pineapple cubes i.e.TSS, pH, acidity, Reducing sugar, Non-reducing sugar, total sugar were significant at p0.05.The best sample of pineapple cubes was, the cubes soaked at 60 o B sugar concentration and exposed to 60 C resulted the best sensory score and the quality characteristics are as follows TSS 32.42%, P H 4.53%, Acidity 0.651%, Reducing sugar 19.09%, Non-Reducing sugar 41.79% and Total sugar 60.87% respectively.