The influence of processing conditions on kinetics, anthocyanin profile and antioxidant activity of purple sweet potato subjected to hot air drying

Purple sweet potato is rich in anthocyanins. The influence of hot air drying on the physical properties, anthocyanin profile and antioxidant capacity of purple sweet potato was explored at six different temperatures (60, 70, 80, 90, 100, and 110 degrees C), three different paving densities and six different dimensions. The results show that the hot air drying kinetics of purple sweet potato were best described by the Page model. The samples dried at 60 degrees C had the highest rehydration rate (2.64), and there was no significant difference between 80 and 60 degrees C. There were no significant differences among the colors of the samples dried at 60, 70, 80, and 90 degrees C, but they were quite different from that dried at 110 degrees C. Four anthocyanins were identified by HPLC-MS/MS as cyanidin 3-sophoroside-5-glucoside, peonidin 3-sophoroside-5-glucoside, cyanidin 3-p-hydroxybenzoylsophoroside-5-glucoside and peonidin 3-p-hydroxybenzoylsophoroside-5-glucoside and determined by HPLC-DAD, and the anthocyanin contents of the samples dried at 80 degrees C were 609.08 +/- 3.26, 82.75 +/- 0.33, 265.88 +/- 0.93, and 179.74 +/- 1.35 mg/100 g DW, respectively. The highest ORAC antioxidant capacity was found in samples dried at 80 degrees C (130.94 +/- 2.59 mu mol TE/g). Based on these studies, 80 degrees C is most suitable for the hot air drying of purple sweet potato. Practical applications Purple sweet potatoes have good antioxidant capacity, which is good for health and loved by consumers. Fresh purple sweet potatoes are not easy to store, but the storage time can be prolonged after hot air drying. This study detected the influence of hot air drying on the drying kinetic, color, rehydration, microstructure, and anthocyanin content of purple sweet potato. Compared with dimension and paving density, the influence of drying temperature is greater. Among six temperatures, 80 degrees C is most suitable for the hot air drying of purple sweet potato. This study provides a theoretical basis for the development and utilization of purple sweet potato as a functional food.