USE OF HYPERBARIC STORAGE AT ROOM TEMPERATURE FOR PRESERVATION OF YOGURT COMPARED TO REFRIGERATION

Hyperbaric Storage (HS) at room temperature (RT) is emerging as a sustainable, energy-saving alternative to traditional refrigeration (RF) for food preservation. This study evaluated the feasibility of HS at 75 and 175 MPa to preserve commercial natural yogurt at RT, assessing its impact on product quality, shelf-life, and safety. A commercial natural yogurt was stored under RF (4 °C) or HS (75 and 175 MPa) at RT, with samples analyzed for spoilage microorganisms (total psychrotrophs, Enterobacteriaceae, yeasts and molds) and lactic acid bacteria (LAB) viability at 0, 3, 6, 24, 48, 96, 120, and 168 hours. Physicochemical properties (pH, titratable acidity, total soluble solids via °Brix, and CIELAB color parameters), syneresis and water holding capacity were also monitored at 0, 3, 24, 48, 120,168, 264 and 504 hours. Spoilage microorganisms remained below the considered detection limit (< 2.70 Log CFU/g) under all tested HS conditions. While LAB viability slightly dropped from 5.18 Log CFU/g at 0 hours to 4.41 Log CFU/g by 168 hours, HS inactivated LAB to below detection limit at 120 h at 75 MPa and 3 h at 175 MPa. Soluble solids and color showed high overall stability, maintaining a total color difference (ΔE*) below 1.52. Under RF, pH and acidity were stable, but syneresis gradually increased up to 53.62 %. At 75 MPa after at 48 h acidification was verified, with a pH drop to 3.82 and a peak in acidity (15.94), while syneresis increased (59.88 %). At 175 MPa, LAB fast inactivation inhibited acidification, resulting in a stable pH (4.11–4.15) and syneresis (~56%). These findings highlight HS as an interesting preservation methodology for yogurt preservation at RT, although LAB inactivation limits the product's conventional "live-culture" status, it offers a practical advantage for ambient-temperature shelf-life extension by effectively preventing over-acidification and pressures lower than 75 MPa should be studied to avoid/minimize LAB inactivation.