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

Area of Science:

• Food Science and Technology
• Microbiology
• Food Engineering

Background:

• Hyperbaric storage (HS) presents a low-energy, low-emission food preservation method using mild pressures at room temperature (RT).
• Watermelon juice (WJ), a nutritious beverage, is highly perishable due to its pH and high water activity (a_W).
• Understanding the impact of a_W on microbial behavior during HS is crucial for its application in food preservation.

Purpose of the Study:

• To investigate the effect of water activity (a_W) on the preservation of watermelon juice (WJ) using hyperbaric storage (HS) at room temperature (RT).
• To evaluate the microbial inactivation and growth of specific bacteria (Escherichia coli, Listeria monocytogenes) and yeast (Saccharomyces cerevisiae) in WJ under varying a_W and HS conditions.
• To compare the efficacy of HS with conventional refrigeration (RF) and atmospheric pressure storage at RT.

Main Methods:

• Inoculation of WJ with target microorganisms (E. coli, L. monocytogenes, S. cerevisiae) at different a_W levels (0.930–0.971).
• Storage of inoculated WJ under hyperbaric conditions (25–75 MPa) at RT for up to 28 days.
• Comparison with control groups stored at atmospheric pressure under RT and RF conditions.

Main Results:

• Hyperbaric storage (HS) effectively controlled microbial growth in WJ, with observed inactivation during storage.
• The efficacy of HS was dependent on a_W, microorganism type, and applied pressure, with greater inactivation at 50–75 MPa and a_W 0.930–0.950.
• Microbial growth was predominantly observed at the highest a_W (0.971), while inactivation was favored at lower a_W and higher pressures.
• Inactivation kinetics were modeled using first-order and Weibull models, with Weibull often providing a better fit.

Conclusions:

• Hyperbaric storage (HS) demonstrates significant potential for preserving watermelon juice (WJ) by controlling microbial growth and inducing inactivation.
• HS offers a more effective preservation strategy than refrigeration for WJ, particularly at reduced water activity and elevated pressures.
• The findings support HS as an environmentally friendlier and energy-efficient alternative for food preservation without the need for temperature control.