CONVECTIVE AIR DRYING CHARACTERISTICS OF GROUND MACADAMIA NUTS

Abstract

Convective hot air drying of ground macadamia (particle size corresponding to 1.29 ± 0.11 mm) was investigated in the temperature and air velocity ranges of 40 to 70 °C and 0.7 to 2.5 m∙s-1, respectively. Page and two-term exponential models were identified in this study as the best semi-theoretical models to describe the thin layer drying of ground macadamia nuts. Both experiments and models revealed that shorter drying times correspond to higher temperatures and smaller granulometries. The effective diffusivity of moisture transfer varied from 3.7 x 10-9 to 4.4 x 10-9 m2∙s-1 and activation energy from 9.57 kJ∙mol-1 to 18.57 kJ∙mol-1 over the temperature and air velocity ranges used in this study. It was also found that when macadamia nuts are reduced to particulate form, diffusivity and activation energy increase.

Keywords

• convective air drying
• dehydration
• drying rate
• macadamia
• modeling
• nuts