Comparing high pressure thermal processing and thermosonication with thermal processing for the inactivation of bacteria, moulds, and yeasts spores in foods

- HPP + heat was better than TS and thermal treatment alone for the inactivation of spores.
- TS was better than thermal processing alone for bacteria and yeast spore inactivation.
- Non-thermal HPP was enough for yeast ascospores inactivation.

Bacterial and fungal spores might germinate/grow after food processing, causing food-borne diseases or food spoilage. High pressure processing (HPP) and power ultrasound are two technologies that can be combined with heat (HPP-thermal or HPTP, TS) to increase the rate of spore inactivation. The objective of this study was to compare HPP, HPTP and TS with exclusively thermal processing to inactivate spores of two pathogenic bacteria (Clostridium perfringens, Bacillus cereus) as well as fruit spoilage microorganisms (Alicyclobacillus acidoterrestris bacteria, Byssochlamys nivea and Neosartorya fischeri moulds, and Saccharomyces cerevisisae yeast). For a 20 min process at 75 °C, 600 MPa HPTP was the best technology for the inactivation of spores of C. perfringens in beef slurry (2.2 vs. 0.9 log for 0.33 W/g TS and no inactivation for thermal treatment). Likewise, at 70 °C 600 MPa HPTP was better to inactivate B. cereus spores in milk than single thermal treatment (4.0 vs. 0.3 log after 20 min process). At 75 °C 600 MPa HPTP was also the best technology for the inactivation of mould ascospores of N. fischeri in apple juice (4.3 log) and B. nivea in strawberry puree (2.0 log) vs. no effect for thermal and even increase in the spores with TS after a 20 min process. TS was a better technology than thermal treatment to reduce A. acidoterrestris spores in orange juice (0.6 vs. 0.2 log after 20 min at 78 °C). Regarding S. cerevisiae ascospores inactivation in beer, non-thermal HPP was much better than TS and thermal processing: 3 log reductions required only 30 s at 400 MPa vs. 5 min for 16.2 W/mL-TS-55 °C and 84 min for 55 °C thermal. Overall, the heat assisted HPP technology was better than TS and thermal treatment alone for the inactivation of bacteria, mould, and yeast spores, requiring lower processing times thus allowing a better food quality.