Combined effects of pulsed electric field and ultrasound on bioactive compounds and microbial quality of grapefruit juice

The combined effect of ultrasound (US) and pulsed electric field (PEF) was investigated on microbial load and bioactive compounds of grapefruit juice. Grapefruit juice was PEF treated (flow rate: 80 ml/min, pulse frequency: 1 kHz, 20 kVcm(-1) electric field strength, temperature: 40 degrees C, time: 600 s) followed by US treatment in an ultrasonic bath cleaner radiating 600 W at frequency of 28 KHz and 20 degrees C for 30 min. PEF and US treatment resulted in a significant reduction in microbial load as compared to the control group. Using combined (PEF+US) treatment, carotenoids, lycopene, anthocyanin contents, and total antioxidant activity were increased from 0.84 g/ml, 0.32 g/ml, 1.37 mg/L, and 177.48 ascorbic acid equivalent mu g/g (control) to 1.26 g/ml, 0.92 g/ml, 1.68 mg/L, and 262.32 ascorbic acid equivalent mu g/g, respectively. The findings demonstrated that PEF+US could be successfully used for preserving bioactive compounds in grapefruit juice while improving the microbial quality for a better shelf-life. Practical applicationsIn recent years, nonthermal techniques, such as sonication and PEF or combination of these are used for the inactivation of microorganism and preserving the bioactive compounds of different juices. The results of the present study revealed that combined treatment (PEF+US) could improve the antioxidant activity, total phenolics, flavonols, flavonoids, lycopene, and total carotenoids. The findings of this study suggested that PEF+US has a potential to improve the quality of grapefruit juice and may be employed for the processing of grapefruit juice at industrial scale.