Effect of a filtered wood smoke treatment compared to various gas treatments on aerobic bacteria in yellowfin tuna steaks

The effect of filtered wood smoke (FS) processing on microbial growth in yellowfin tuna steaks was investigated. Steaks were treated for 32h and then subjected to aerobic storage for 8 days and levels of aerobic bacteria studied. The FS treatment was compared to untreated tuna (exposed to air), 100% nitrogen (N-2) (to investigate the specific effect of oxygen exclusion), 100% carbon monoxide (CO) (to investigate the effect of the CO molecule) and artificial FS (to investigate a gas with all the same gas compounds except for the smoke compounds). A study was also conducted with 21% carbon dioxide (CO2) to investigate the effect of CO2, which is found in both FS and the artificial FS. The results show that all treatments effectively (P<0.05) reduced aerobic microorganisms compared to the untreated control after 32 h, possibly due to an oxygen exclusion effect as well as to the presence of other active compounds in the gases. However, only FS, artificial FS, 100% CO and 21% CO2 treatments had a significant (p>0.05) residual antibacterial/bacteriostatic effect post-treatment. The FS treatment had the most significant residual effect (p<0.05), and this study strongly suggests this effect is due to the presence of CO2, smoke components and CO. (C) 2007 Published by Elsevier Ltd. on behalf of Swiss Society of Food Science and Technology.