STUDIES ON THE USE OF CARBON DIOXIDE DISSOLVED IN 

 REFRIGERATED BRINE FOR THE PRESERVATION OF WHOLE FISH 



Harold J. Baknett, Richard W. Nelson, Patrick J. Hunter, 

 Steven Bauer, and Herman Groninger' 



ABSTRACT 



Although storing fish in refrigerated seawater has many advantages over storing them in ice, the use 

 of refrigerated seawater also has several disadvantages, one of vi'hich is the difficulty in controlling 

 the growth of spoilage bacteria in the fish. Reported here is the effect on the growth of bacteria in 

 rockfish and chum salmon of dissolving carbon dioxide in brine. Storing the fish in the refrigerated 

 brine treated with carbon dioxide inhibited the growth of the bacteria, retarded the rate at which the 

 fish decrease in quality, and increased their storage life by at least 1 week. 



Refrigerated seawater as a medium for cooling, 

 storing, and transporting fish has many advan- 

 tages, which have been well documented (Idyll, 

 Higman, and Siebenaler, 1952; Osterhaug, 1957; 

 Cohen and Peters, 1962; Peters and Dassow, 

 1965; Roach et al., 1967). 



This medium, however, also has disadvant- 

 ages. These include the excessive uptake of 

 water by species of low oil content, such as sole 

 and cod, and an increase in total salt. Con- 

 trolling the growth of spoilage bacteria in fish 

 stored in refrigerated seawater also presents a 

 problem (Roach et al., 1967). This problem 

 results from the blood, dissolved protein, and 

 visceral contents accumulated in the seawater 

 during the storage of the fish. For these reasons, 

 fish held in refrigerated seawater are not nec- 

 essarily of better quality than are those held 

 for the same period in ice. Nor can fish neces- 

 sarily be held longer in refrigerated seawater 

 than in ice before spoilage occurs. 



This laboratory recently began a study of 

 methods for increasing the effectiveness of re- 

 frigerated seawater as a medium for preserving 

 fish. The investigation is timely because fish- 

 ermen are finding it increasingly difficult to lo- 

 cate catches on traditional fishing grounds. This 

 reduced abundance requires longer stays at sea, 

 which sometimes result in the landing of fish 

 of less than optimum quality. 



' National Marine Fisheries Service Technological 

 Laboratory, Seattle, Wash. 98102. 



^fanuscript received January 1971. 



FISHERY BULLETIN: VOL. 69. NO. 2. 1971. 



Use of carbon dioxide gas dissolved in re- 

 frigerated seawater seemed promising as an in- 

 hibitor of the spoilage bacteria. Stansby and 

 Grifliths (1935), for example, found that whole 

 haddock and haddock fillets stored in an atmos- 

 phere of carbon doxide kept almost twice as long 

 as did those stored in air. Castell (1953) dem- 

 onstrated that carbon dioxide showed promise 

 of being a useful presei-vative for salted fish held 

 in 12';r brine. Carbon dioxide has been used 

 effectively to extend the storage life of refri- 

 gerated meat and poultry products (Wheaton, 

 1960) and is known to have bacterial inhibiting 

 properties (King and Nagel, 1967). Fiskeri- 

 ministeriets Forsogslaboratorium (1968) noted 

 that, in limited experiments on holding fish in 

 tanks, carbon dioxide decreased the rate at 

 which their quality was degraded. Wayne I. 

 Tretsven (1968, personal communication) 

 showed that the shelf life of fresh silver salmon 

 refrigerated in a mixed atmosphere of carbon 

 dioxide, oxygen, and nitrogen was significantly 

 extended beyond that of fresh silver salmon 

 refrigerated in air. 



Rockfish is normally iced aboard the fishing 

 vessel and may be held for as long as 7 to 10 

 days before being landed. Chum salmon is fre- 

 quently held in refrigerated brine aboard can- 

 nery tenders and may be held aboard the ves- 

 sel for as long as 7 days. With both methods 

 of holding, the quality of the fish may be poor 

 if they must be held for longer periods. This 



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