Response surface methodology for optimisation of hot air drying of blackcurrant concentrate infused apple cubes

Response surface methodology was used to investigate the effects of temperature, air velocity and loading density on the drying of infused apple and to determine the optimised conditions for hot air drying. The drying behaviour at different temperatures, air velocities and loading densities of infused apple cubes behaved similarly to fresh and osmotically pre-treated apples. The hot air drying of infused apple cubes consisted of a very short constant rate period and two falling rate periods. The drying of the samples was most influenced by temperature followed by air velocity, then loading density. The optimised conditions for drying the infused apple cubes were a drying temperature of 80°C, air velocities of 1.50 to 1.85 m/s and loading densities of 6.35 to 7.08 kg/m², which resulted in short drying times of 99 to 104 minutes.