Effect of Heating Pre-Treatments and Cracking Methods on the Whole Candlenut Kernel Yield

Post-harvest handling of candlenut requires special attention to get the best quality whole kernel and high selling price. The cracking of candlenut traditionally and mechanically using a ripple mill equipment produces a low whole kernel yield. This research aims to find the best handling method of candlenut to obtain the maximum whole kernel yield. The heating pre-treatments using hot air were used to heat up the candlenuts under different temperature variations (80, 90, 100 °C) and heating durations (3, 4, 5 h). The hot air was generated by a heat gun with a flow rate of 500 L/min. After drying, the candlenut was soaked in the water with a temperature of 5 °C for 20 min. The process of cracking candlenut was carried out by two methods: method-1 by dropping candlenuts from several altitudes, i.e., 1, 2, 3, 4, 5 m above the concrete surface and method-2 by dropping a load of 100 g to the candlenut from several altitudes (0.2, 0.4, 0.6 and 0.8 m). The results showed that the optimum pre-treatment that produces the highest whole kernel yield (91.67%) was heating with a temperature of 90 °C for 3 h and by dropping candlenut from an altitude of 5 m (method-1). The momentum needed to break the candlenut shell without damaging the kernel are 0.096 kg.m/s with momentum velocity of 9.905 m/s. This optimal momentum data can be further used for the development of centrifugal-type candlenut cracking equipment.