Conveyor belt catalytic infrared as a novel apparatus for blanching processing applied to sweet potatoes in the industrial scale

Abstract In this study, effects of conveyor belt catalytic infrared blanching (CBCIRB) on peroxidase (POD), moisture reduction, physical and chemical properties, and microstructure of sweet potato slices were investigated. The parameters of CBCIRB were infrared irradiation distance (6, 12, and 18 cm), sample thickness (3, 5, and 7 mm), and conveyor speed (0.7, 0.35, 0.1 m/min, etc.). Meanwhile, the effect of conventional hot water blanching (HB) on sweet potato slices were also investigated. The results showed that shortening the infrared irradiation distance and reducing the slice thickness could both accelerate the POD inactivation rate. When 90% POD inactivation was achieved, CBCIRB samples yielded better hardness and higher preservation of phytochemicals than HB samples. The appropriate CBCIRB parameters were the slice thickness of 3 mm, infrared radiation distance of 12 cm and conveyor belt speed of 0.16 m/min, the moisture reduction, surface colour change, hardness, vitamin C retention rate, β-carotene retention rate, and total phenol content were: 78.34%, 7.41, 1690.4 g, 75.16%, 133.49%, and 1.03 mg/g, respectively. The microstructure observation showed that the damage of sweet potato slice cells by HB was more severe than CBCIRB. Overall, CBCIRB achieved higher product quality in a relatively uniform air environment.