Microbiological and Chemical Changes During Storage of Swordfish ( Xiphias gladius ) Steaks in Retail Packages...

Swordfish ( Xiphias gladius ) steaks were held in retail packages containing 100% CO₂ and in mixtures of 40% and 70% CO₂ in combination with either oxygen or nitrogen. Controls were stored in air. Samples were removed for chemical and microbiological analyses after 2-22 d of storage at 3.5°C. The inhibitory effect of CO₂ on psychrotrophic, aerobic gram-negative spoilage bacteria was proportional to the CO₂ tension in the packages. Maximum inhibition of growth was achieved with 100% CO₂. Except for steaks stored in 40% CO₂:60% O₂ heterofermentative Lactobacillus spp. became a dominant part of the microflora of steaks stored in CO₂-enriched atmospheres. Pseudomonas spp. continued to be a major part of the microflora of steaks stored in 40% CO₂:60% O₂. During the first 2 d of storage, there was a decrease in the surface pH of the swordfish steaks proportional to the CO₂ tension in the packages. Swordfish steaks stored in CO₂-enriched atmospheres had lower total volatile nitrogen (TVN), trimethylamine (TMA) and total volatile acid (TVA) values than steaks stored in air. Oxidative rancidity was not a flavor problem of fish in any of the atmospheres after 20 d of refrigerated storage.