Influence of number of puffing times on physicochemical, color, texture, and microstructure of explosion puffing dried apple chips

The impact of number of puffing times during explosion puffing drying (EPD) on drying characteristics and qualities of apple chips was studied. Physicochemical characteristics, antioxidant capacity, color, texture, expansion ratio, rehydration ratio, hydroscopicity, and microstructure of apple chips dried by EPD with 0 (vacuum drying, VD), 1, 3, 5, 7, and 9 puffing times were analyzed. The apple chips dried by EPD with 3 and 5 puffing times exhibited better color (ΔE 7.27–7.70) and texture (hardness 40.5–40.8 N, crispness 8.8–9.3 N/mm), as well as higher expansion ratio (104.4–109.7%) compared to VD and EPD with fewer or more puffing times. The samples dried with 3 and 5 puffing times also showed relatively higher rehydration ratio and hygroscopicity, and acceptable retention of total phenolic content (0.32–0.37 mg/g) and ascorbic acid content (1.66–1.89 mg/100 g), as well as considerable antioxidant abilities (DPPH 79.45–81.17 AEAC µM/g, FRAP 66.54–68.25 TEAC µM/g, ABTS 73.36–79.21 TEAC µM/g) compared to VD dried samples. In conclusion, experiments with apple chips indicated that EPD drying with 3 to 5 puffing times yielded superior overall quality than that with more or fewer puffing times.