Radio frequency puffing of purple sweet potato nutritious snacks

Abstract

Radio frequency (RF) heating is a new technology applied to puffing drying that has the potential to replace conventional drying methods. The heating and puffing effects of sample thickness (1–3 mm), electrode gap (110–130 mm), and moisture content (40–60%), of the composite purple sweet potato chips were studied. The optimal process parameters were 1 mm sample thickness, 110 mm electrode gap, and 60% moisture content. The effects of four drying methods, including RF, microwave (MW), vacuum freezing (VF), and hot air (HA), on the chips were compared. The physicochemical properties of the chips were evaluated in terms of nutrient composition, color, hardness, rehydration ratio, moisture content, and microstructure. The RF-dried samples showed the second-highest anthocyanin retention of 8.74 mg/100 mg, the smallest color difference ΔE of 8.67, a satisfactory hardness of 752 gf, and the highest rehydration ratio of 3.42. Microstructure analysis revealed that RF drying could gelatinize the majority of the starch granules and change their structure. Future studies should focus on minimizing the adverse impact of RF heating to maintain the quality of nutritious snacks.