Effects of hot air-assisted radio frequency roasting on quality and antioxidant activity of cashew nut kernels

This study investigated hot air-assisted radio frequency (HA-RF) roasting effects on physicochemical properties, sensory quality, and antioxidant activity of cashew nut kernels. Raw cashew nut kernels placed inside polypropylene cuboid containers with different sample thickness (7 cm and 5 cm) were roasted by HA-RF treatments. Uniformity of roasted sample moisture content and color, sensory attributes (9-point hedonic scale), and antioxidant activity (TEAC and DPPH radical scavenging capacity) were evaluated. Roasting temperature of 120-130 °C and sample thickness of 5 cm were selected based on sample uniformity. For kernels with initial moisture content of 6.2 g/100 g (d. b.), HA-RF roasting reduced moisture content to 1.5 g/100 g within 30 min. Peroxide value and acid value of HA-RF roasted samples were significantly (p<0.05) lower than those roasted by conventional hot air at 140 °C for 30 min, indicating better physicochemical quality of samples roasted by HA-RF heating. Both sensory attributes and antioxidant activity of the kernels roasted by HA-RF were in well-acceptable range, and had no significant difference (p>0.05) compared with the samples roasted by conventional hot air method. This study demonstrated that HA-RF roasting holds great potential for roasting cashew nut kernels in a more efficient and environmental-friendly pattern.