Lipase activity and flavor of air-dried duck meat under different treatments. Neutral lipase (A); acidic lipase (B); phospholipase (C). Radar plots of E-nose response data (D); E-nose principal component analysis score plots (E); GC–MS principal component analysis score plots (F); volatile flavor substances heat map (G). Data are expressed as mean ± standard deviation. Different letters (a-f) indicate statistically significant differences (p < 0.05). CK: untreated; US: ultrasonication (250 W, 4 min, 30 °C, 40 kHz); L: inoculation with L. fermentum CGMCC 1.7434; D: inoculation with D. hansenii GDMCC 2.149; LD: inoculation with L. fermentum CGMCC 1.7434 and D. hansenii GDMCC 2.149; US-LD: inoculation with L. fermentum CGMCC 1.7434 and D. hansenii GDMCC 2.149 after ultrasonic pretreatment (250 W, 4 min, 30 °C, 40 kHz).