BACTERIOLOGICAL AND COLOR CHANGES IN MODIFIED ATMOSPHERE-PACKAGED REFRIGERATED CHANNEL CATFISH

Channel catfish (Ictalurus punctatus) fillet strips were packaged unde r aerobic (AIR), 25% carbon dioxide (CO2) (LC) and 80% CO2 (HC) enviro nments with the remainder being air; and stored at 2 and 8 degrees C f or 4 weeks. Aerobic plate counts (APC) for HC fish at 2 degrees C decl ined from 6 log CFU/g to 1.4 log CFU/g after 2 weeks but increased to 5 log CFU/g by the third week. The HC-stored strips at 8 degrees C had an initial increase in APC followed by a decline to 1.4 log CFU/g on the third week, and a rise to 9 log CFU/g by the fourth week. Aerobic plate counts in AIR- and LC-packed fish at either temperature increase d steadily throughout storage. Fish surface pH declined in HC-packed p roduct from 6.2 to 5.6 by the fourth week, but did not change in LC an d AIR packs. Hunter L-values increased in CO2-packed products, while H unter a-values decreased. Listeria monocytogenes was isolated from fis h under LC and AIR at 8 degrees C in the second and third weeks. Salmo nella spp. was present in fish stored in all storage atmospheres at 8 degrees C, but only in AIR-packed fish at 2 degrees C. Clostridium bot ulinum was not found in product at any of the storage atmospheres at e ither temperature at any time. The best treatment was fish packed in H C and stored at 2 degrees C.