Orange juice processing using a continuous flow ultrasound-assisted supercritical CO2 system: Microbiota inactivation and product quality

The feasibility of using supercritical CO2 assisted by ultrasound (SC-CO2-HPU) in continuous mode (3.06 min residence time) for the non-thermal pasteurization of orange juice was evaluated. The proposed technology was effective for microbial inactivation; complete inactivation was obtained for E. coli and total aerobic mesophilic bacteria while 99.7% reduction for S. cerevisiae. Results showed that the SC-CO2-HPU treatment brought about small changes in the pH, Brix and titratable acidity of the juice. Furthermore, although SC-CO2-HPU technology produced a higher browning index (211%) and greater changes in color, it was possible to improve the cloud of juice by 173%; what is more, a smaller percentage of phenolic compounds (6.5%) and ascorbic acid (5.5%) was lost compared to the thermally pasteurized juice (10% decrease in both parameters). Moreover, the antioxidant capacity could be increased (12%) with respect to the natural juice. Therefore, SC-CO2-HPU technology appears to be effective for microbial pasteurization and the mild process conditions used could lead to an increase in the juice quality. Industrial relevance: The demand for high quality processed foods which preserve their natural and fresh-like characteristics has awakened a growing interest in non-thermal technologies. The ultrasound-assisted SC-CO2 continuous system is an innovative non-thermal technology that could represent a development in the area of emerging technologies. This technology allows high quality products to be obtained by preserving their natural bioactive compound content while maintaining their fresh-like organoleptic characteristics. In fact, food experts working in academia, industry or governmental agencies worldwide foresee that non-thermal emerging technologies will be among the most impactful novel food processing technologies for the next decade in terms of product commercialization.