Nonthermal inactivation of heterogeneous and superdormant spore populations of Bacillus cereus using ozone and high pressure processing

• Inactivation of superdormant spores using nonthermal technologies is investigated.
• Superdormant spores were more resistant to ozone than heterogeneous populations.
• Psychrotolerant sporeformers were more resistant to ozone than mesophilic species.
• Ozone and HPP combined treatment achieved a 2.67-log CFU/mL reduction.

Superdormant spores are those which germinate extremely slowly compared to the majority of the spore population. The development of a method to isolate large quantities of superdormant spores in a laboratory setting has allowed for further study of these hardy organisms. In this study, the ability of nonthermal processing technologies, including a combined hurdle technology of aqueous ozone and high pressure processing (HPP), to inactivate superdormant spore populations of mesophilic and psychrotolerant isolates of Bacillus cereus was investigated. Superdormant spores were approximately 20% more resistant to ozone treatment than heterogeneous spore populations (p = 0.02) and psychrotolerant species were approximately 31.9% more resistant than mesophilic species (p = 0.004). The combined ozone-HPP hurdle technology achieved a maximum 2.67-log CFU/mL reduction of superdormant spores.Industrial relevanceNonthermal processing technologies including high pressure processing (HPP) and ozone have high implications for reducing the number of spores in foods; however, these technologies are not widely utilized in the industry due to their inability to completely inactivate all the spores within a product. The spores that do not germinate as easily as the majority of a spore population are known as superdormant spores. This study demonstrates that an ozone-HPP combined hurdle technology may be able to effectively reduce the number of superdormant spores, specifically psychrotolerant sporeforming toxin-producing species such as B. cereus and Bacillus weihenstephanensis, in refrigerated food products such as RPFEDs and reduce the risk of foodborne illness.