EFFECT OF CARBON-DIOXIDE AND OXYGEN-ENRICHED ATMOSPHERES ON MICROBIOLOGICAL-CHANGES AND CHEMICAL-CHANGES IN REFRIGERATED TUNA (THUNNUS-ALALUNGA) STEAKS

Bacterial populations and several physicochemical parameters (metmyoglobin, pH, total volatile nitrogen, nucleotide breakdown products, nonvolatile amines, lipid autoxidation, and short-chain fatty acids) and sensory attributes (odor and color) were measured in refrigerated tuna steaks stored at 2 degrees C in air, CO2/air (20/80) (v/v), CO2/air (40/60) (v/v), and CO2/O-2 (40/60) (v/v) atmospheres. The effects of modified atmospheres on bacterial growth and physicochemical parameters are discussed. From a microbiological point of view, the shelf life of refrigerated tuna steaks was extended about 1 week when CO2 enriched atmospheres were used. Metmyoglobin formation was minimum when the atmosphere was enriched with O-2. Therefore, the most effective atmosphere was CO2/O-2 (40/60) (v/v), in which the shelf life of tuna may be doubled with respect to both microbial condition and color appearance.