Microbial inactivation during hyperbaric storage of food: Current data, impacting factors and the potential of a novel pasteurization methodology

Background: Hyperbaric Storage (HS) is a food preservation methodology that stores foods for long periods inside vessels at pressure levels above atmospheric pressure. HS has been studied for different perishable products, showing good results for food safety and quality and shelf-life extension, frequently at uncontrolled room temperature. Studies reported HS's ability to control microbial growth and cause microbial inactivation during storage. Scope and approach: This review seeks to investigate the inactivation of different microorganisms observed in HS studies at variable storage conditions (pressure level, storage duration and temperature). The maximum inactivation seen in these studies is presented and discussed, along with an examination of how those variables and other factors (food composition, pH and water activity (aW)) impact inactivation. Additionally, the potential of a novel pressure pasteurization method, moderate pressure pasteurization (MPP), is discussed. Key findings and conclusions: In HS studies, microbial inactivation frequently reached levels below the detection limit, including reductions of over 6 log units. Varying storage conditions impacts the inactivation as, typically, increasing the pressure level and the temperature results in higher and/or quicker reductions. Storage duration depends on HS purpose, but studies range from hours up to one year with considerable inactivation results. Other possible impacting factors include the type of microorganism, as Gram-negative bacteria appear to be less pressure resistant; the food composition; and the pH and aW: a low pH and high aW often facilitate inactivation. Inactivation results exceeding 5 log units after storage at moderate pressure levels for a few hours highlighted MPP as a potential novel nonthermal pasteurization methodology.