Optimisation of processing conditions for infrared drying of cashew kernels with testa

Cashew kernels are thermally processed to facilitate the removal of their outer skin (testa).
Infrared (IR) processing of cashew kernels for differential drying is a novel approach. Processed cashew
kernels are valued for their colour, size and texture. The kinetics of colour change and the effect of thermal
processing on compressive strength (indicator of brittleness) during IR drying of cashew kernels were
investigated. Kernels with testa were dried for different durations (15–55min) over a range of temperatures
(55–95 ◦C). The change in colour was expressed as total colour difference and browning index. The colour
values increased with increasing drying temperature and duration, indicating darkening of the kernel
colour. Increase in drying duration reduced the compressive strength, imparting the desired brittleness
to the kernel. Optimisation of the drying conditions by response surface methodology and the peelability
factor indicated that the best results could be obtained when cashew kernels were dried at 55 ◦C for 55min.