Synergic effect of multi-frequency thermosonication and germinant on Alicyclobacillus acidoterrestris spore inactivation and underlying mechanisms

Alicyclobacillus acidoterrestris spores have strong stress resistance, and their spores cannot be eliminated by pasteurization, which is considered a major threat to the beverage industry. In this study, based on the spore control strategy of “germinate to eradicate”, the spores were germinated by multi-frequency thermosonication (MFTS) combined with germinant. The process parameters were optimized, and the underlying mechanism was explored. The results showed that when A. acidoterrestris spores were treated with MFTS (60 °C, 20/40/50 kHz) and 300 mM AGFK for 30 min, incubated at 45 °C for 2 h, and heated to 80 °C for 20 min, a maximum 1.4 ± 0.04 log reduction can be achieved. The spores showed the darkest phase and the best germination effect after MFTS treatment, but leakage of proteins and electrolytes inside the spores were also caused. The surface of the vegetative cells formed by spore after MFTS treatment shrank extensively, and the shape was irregular. Spore resistance was reduced, making them more likely to die after pasteurization. This study could provide theoretical evidence for the technological innovation and practical application of A. acidoterrestris spores hazard control in the beverage industry.