# Water Activity Effect on Microbial Behavior During Hyperbaric Storage at Room Temperature of Watermelon Juice as a Case Study

## TL;DR

This study explores how water activity and hyperbaric storage affect microbial growth in watermelon juice, showing it can preserve food more sustainably than refrigeration.

## Contribution

The study introduces hyperbaric storage as a novel, energy-efficient preservation method for watermelon juice based on water activity and pressure.

## Key findings

- Hyperbaric storage at 50–75 MPa and lower water activity (0.930–0.950) increased microbial inactivation.
- Weibull kinetic models better described microbial inactivation than first-order models.
- Hyperbaric storage outperformed refrigeration in controlling microbial growth without temperature control.

## Abstract

Hyperbaric storage (HS) is a novel technology for storing foods under mild pressures that, when used at room temperature (RT), offers much lower energy costs and greenhouse gas emissions than conventional refrigeration (RF). Watermelon juice (WJ), with interesting associated health benefits, is highly perishable due to its pH (5.20–6.70) and water activity (aW, 0.97–0.99). This work investigated aW’s impact on WJ’s preservation by HS/RT, studying the behavior of Escherichia coli, Listeria monocytogenes, and Saccharomyces cerevisiae inoculated in WJ at aW 0.930–0.971 stored at 25–75 MPa for up to 28 days, along with RT and RF atmospheric pressure controls. The results showed that HS could control microbial growth, and, during storage, inactivation was also observed, and that HS’s impact depended on the aW level, microorganism, and storage pressure. Inactivation was often increased at 50–75 MPa and at aW 0.930–0.950, while growth mostly occurred at aW 0.971. The inactivation curves were mathematically described by the first-order and Weibull kinetic models, with the Weibull model frequently obtaining better fits. These findings support HS’s potential for food preservation, showing better overall WJ growth control and inactivation effects than RF, without temperature control, making HS environmentally friendlier.