624 U. S. BUREAU OF FISHERIES 



EFFECT OF ICE ON FISH 



Ice has no sterilizing effect on fish. If impure, it may have the 

 opposite effect. It kills few. if any, bacteria, but by its cold only 

 retards their growth. Neither does it arrest autolysis, but only 

 retards it. The water produced by melting ice coming in contact 

 with fish dissolves some of the soluble substances and causes some 

 swelling and blanching of the tissues. It may also crush or bruise 

 the fish, promoting autolysis instead of arresting it, and the water 

 may cause a bleaching of the colors in the skin of fish. 



To overcome the dissolving and bleaching effect of ice, sea-water 

 ice has been tried for fish, but the use of this ice does not seem to 

 have been adopted in practice. (See Larsen's method of chilling,, 

 p. 621.) 



CHEMICAL PRESERVATIVES IN ICE 



Attempts have been made also to fortify the preserving effect of 

 ice by the addition of chemical preservatives. Sodium hypochlorite 

 was tried and excited much interest in the industry a few years ago. 91 

 A solution containing sodium hypochlorite was sold under a trade 

 name to be put in the water to be frozen. However, on investigations 

 made by the British Food Investigation Board, 92 sodium hypo- 

 chlorite failed to give promising results. In concentrations low 

 enough not to taste or not to be injurious to health it failed to have 

 any noticeable preserving effect. The same was found to be true 

 of formaldehyde. They also investigated homoflavine and crystal 

 violet, two dyes that are relatively harmless to man but exceedingly 

 toxic to bacteria. In the presence of 0.1 per cent of ordinary salt 

 these dyes will freeze uniformly in ice, but in permissible concentra- 

 tions they failed to have any useful preserving effect. 



The methods of using ice for fish are too well known to require 

 lengthy description, but certain details are worthy of notice. Ice 

 taken aboard trawlers and other fishing boats is usually crushed. 

 Ice companies deliver the ice at the wharf, crush it, and chute it into 

 the holds. Some fish freezers manufacture ice as a side line 

 and crush it for the fishing boats. At some places elaborate arrange- 

 ments are provided for this purpose, as at the Commonwealth Fish 

 Pier in Boston. Aboard the boats the crushed ice is contained in 

 barrels, boxes, bins, or loose in the holds. The customary method 

 of packing is to alternate layers of ice and fish and cover the heap 

 with a generous amount of ice. This practice is followed in the 

 banks trawler fisheries of the East and the salmon, halibut, and 

 cod fisheries of the west coast, and for snapper and other fisheries 

 of the Gulf of Mexico. 



DRESSING FISH FOR ICING 



Large fish nearly always are gutted before being iced. This 

 applies to cod, haddock, hake, pollock, halibut, and salmon. The 

 heads are left on as a protection of the flesh, but in the case of hali- 



81 For particulars see Gibhs, Proceedings of the Fourth International Congress of Re- 

 frigeration, London. 1924. Vol. II, sec. Ill, pp. 1222-1244. 



92 Great Britain, Report of the Food Investigation Board for 1923, pp. 8-10. London. 



