Ultrasound-assisted vacuum impregnation on the fortification of fresh-cut apple with calcium and black carrot phenolics

•Effect of simultaneous use of ultrasound during vacuum impregnation was investigated.•Ultrasound was effective on compound transfer rate at both vacuum and restoration periods.•The growth of psychrophilic and mesophilic bacteria were affected by vacuum impregnation. This study evaluated the simultaneous effect of ultrasound on vacuum impregnation process to enhance infusion of calcium lactate and black carrot phenolics into ready to eat apple tissues. A vacuum – ultrasonic equipment was developed for this purpose and effects of different ultrasound powers (96–198 W) at 35 kHz and stage of ultrasound application at vacuum and restoration periods were investigated. The simultaneous application of 130 W ultrasound during vacuum impregnation did not rupture cellular integrity, but it led to increases in calcium content (13.8%), total phenolics (11.8%), total flavonoids (17.3%), total anthocyanins (24.6%) and antioxidant capacities (23.6%) of apple discs compared to non-ultrasound vacuum impregnation. In addition, total population of psychrophilic and mesophilic microorganisms were enumerated in both black carrot infused and non-infused samples and results showed that ultrasound-assisted vacuum impregnation treatment in the presence of black carrot phenolics were highly effective on inhibition of microorganisms growth in apple discs over storage period.