Application of ultraviolet radiation and ultrasound treatments for Alicyclobacillus acidoterrestris spores inactivation in apple juice

Alicyclobacillus acidoterrestris is a spore-forming bacterium, which is responsible for quality degradation of fruit juices. Non-thermal treatments, such as ultraviolet-C radiation (UV-C) and ultrasound (US), are promising methods for microbial inactivation. The main objective was to study the influence of UV-C, ultrasound and combinations of both treatments on A. acidoterrestris spores inactivation in apple juices. A thermal treatment at 95 °C was used as control. Commercial juices artificially inoculated with the bacterium were exposed to the treatments. Results showed that ultrasound had the lowest impact on A. acidoterrestris inactivation. When UV-C radiation was applied, the number of spores decreased drastically after 8 min, being more effective than a 95 °C thermal treatment. In terms of final microbial loads, combination of US and UV-C did not result in synergetic effects. However, inactivation rates of the combined treatments were significantly different from the ones obtained when the treatments were applied individually.