Impact of Fruit Ripeness on Physicochemical Properties and Convective Drying Characteristics of Kent Mango (Mangifera indica L. cv. 'Kent')
Résumé
Impact of ripeness on drying characteristics of mango was studied by considering different zones on the fruit. For each zone, ripeness was estimated by total soluble solids/acidity ratio, colour and texture of fruit flesh. For each state of ripeness, drying curves and time-temperature curves were established both in forced and natural convection. Mass diffusivity (estimated by considering two diffusion regions), thermal diffusivity and drying rates were deduced from these drying curves by considering product shrinkage. Results showed that the time required to reduce moisture content to any given level depended on the ripeness state, being highest for unripe samples and lowest for ripe samples. At each drying moment, temperature of ripe sample was higher than that of unripe sample. Mass diffusivity, thermal diffusivity and drying rates strongly increased with ripeness state. At 60°C, unripe and ripe fruit mass diffusivities ranged respectively from 1.69x10-10 to 9.87x10-10 m²/s and 3.38x10-10 to 1.77x10-9 m²/s. Thermal diffusivities ranged from 2.12 x10-11 to 6.44x10-10 m²/s and 2.74x10-10 to 8.05 x10-10 m²/s respectively for unripe and ripe samples. In natural convection, drying rates reached maximal values of 0.16 kg m-2 s for unripe sample and 0.47 kg m-2 s for ripe sample whereas in forced convection they reached respectively 0.43 and 0.67 kg m-2 s. Product shrinkage decreased with ripeness and was almost ideal for the major part of the drying process. Constants of suitable fitting models also varied considerably with fruit ripeness. This work showed that ripeness state influences strongly drying characteristics of mango fruit.