HYPERBARIC STORAGE AS A METHODOLOGY TO HURDLE AND DESTROY ALICYCLOBACILLUS ACIDOTERRESTRIS AND BYSSOCHLAMYS NIVEA SPORES AT ROOM TEMPERATURE

Alicyclobacillus acidoterrestris (ACB) and Byssochlamys nivea (BN) spores are frequently found in acidic fruit juices and are known for their resistance to thermal and nonthermal pasteurization (requiring temperatures >100 ºC for being effectively destroyed). Unlike many other spores, they are capable of germinating and growing at pH levels below 4.6, which can lead to spoilage during storage. This deterioration is associated with the formation of guaiacol in the case of ACB and can cause also food poisoning due to the production of mycotoxins (like patulin, which is also carcinogenic) for BN. Refrigeration is widely used to delay spore development, limiting the products’ shelf-life. Hyperbaric storage (HS) has been proposed as an alternative to refrigeration, and it states the application of low/moderate pressures to hurdle microbial development, instead of low temperatures like in refrigeration. This way, HS/RT (50–250 MPa) was assessed for controlling spores of ACB and BN in apple juice (pH 3.70, 10 ºBrix) and subjected either to thermal (80 °C, 30 sec) or high pressure (600 MPa, 3 min, HPP) pasteurization to mimic a scenario of a juice contaminated with ACB and BN spores subjected to commercial pasteurization conditions. Following these treatments, samples were stored under HS/RT conditions for up to 30 days. The results showed that HS/RT effectively avoided ACB and BN spore development, leading to their gradual inactivation during storage. For BN, an initial pasteurization step (either by TP or HPP) proved essential, achieving approximately a 3-log reduction at 150 MPa and reducing counts below detection limits after 5 days. For ACB, spores were inactivated regardless of prior thermal or HPP pasteurization, showing an overall reduction ≥5-log units after one day at 150 MPa. Phase-contrast microscopy revealed that spores did not form vegetative cells under HS/RT conditions, thereby preventing the production of guaiacol (for ACB) and patulin (for BN), despite of being at RT. These results highlight HS/RT as a promising method to inhibit the development of bacterial and fungi spores, as well as a tool to destroy spores at RT, without thermal input on the product.