Effect of gas packaging conditions on thawed Thunnus obesus preservation

Shelf-life of commercial thawed tuna was studied in different packaging atmospheres: Air, High O2 (70%O2/30%CO2), Sprayed green tea extract in High O2, Low O2 (40%O2/40%CO2/20%N2), Non O2 (60%CO2/40%N2) and Carbon monoxide (60%CO2/39.5%N2/0.5%CO). Three-cm-wide slices were analysed at days 0 (24 h post-thawing), 4 and 6 from the date of packaging while kept in retail conditions. Analysis performed each day of the study were: gas concentration in the headspace, colour, pH, exudative losses, lipid oxidation, total volatile bases nitrogen, microbiological analysis and a sensory test (fresh and cooked fish). The atmospheres 'Non O2' and 'Low O2' were the most effective for increasing tuna shelf-life due to better general lipid oxidation characteristics, microbial counts and sensory results. Shelf-life reached up to 6 days post-thawing in these cases although tuna should be consumed cooked to prevent risk of pathogens or toxins. Also, the use of antioxidants or carbon monoxide improved colour and flavour attributes and should be considered as alternatives for packaging.