Pre-shelling parameters and conditions that influence the whole kernel out-turn of steam-boiled cashew nuts

This work investigates the effect of moisture content (MC), nut size distribution and steam exposure time (SET) on the whole kernel out turn (WKO) of cashew nuts during shelling using a 3 x 5 x 4 factorial experiment. Three nut sizes: small (18–22 mm), medium (23–25 mm) and large (26–35 mm); five levels of MC: 8.34%, 11.80%, 12.57%, 15.40%, 16.84% (wet basis) and four levels of steam exposure time (SET): 28, 30, 32, and 34 min were considered. Nuts were conditioned with warm water to the desired moisture content of 8.34%,11.80%, 12.57%, 15.40% and 16.84% (wb); and steam-boiled at 700 kPa for 28, 30,32, and 34 min. The pre-treated nuts were shelled using a hand-operated cashew nuts shelling machine. The results showed that the single effect of MC, steam exposure time (SET) or nut size distribution is not enough for estimating WKO; it is rather by an interaction of these parameters. The optimum WKO of steam-boiled nuts was 91.74%, 90.94% and 87.98% for large, medium and small sized nuts at MC*SET combination of 8.34%*30 min, 11.80%*32 min and 8.34%*30 min, respectively. Pre-treatment of cashew nuts by steam boiling was found to improve whole kernel out-turn of the cashew nut. Whole kernel out-turn decreased as MC increased, thereby limiting the need for moisture adjustment when nuts are to be processed by steam boiling.