550 



U. S. BUREAU OF FISHERIES 



ductivity of the fish is not any too good, and the fish is surrounded by 

 water warmer than itself. The heat given up by the water in freezing 

 is taken up by the outer part of the fish, but is conducted inward rather 

 slowly, so that if the fish is left in the water too long the outer part 

 of it is thawed. It is better to lift the fish out of the water in order 

 to give the heat time to be conducted into the interior of the fish and 

 also, if the air of the room is cold, to take advantage of the refrigera- 

 tion in the air. If a thicker glaze is required, the fish may be dipped 

 a second or third time. Excessively thick glaze is usually undesir- 

 able because customers may object to the undue increase in weight; 

 and, also, too thick a glaze may crack on handling. The ideal glaze 

 is clear, smooth, comparatively thin, free from roughness, and uni- 

 formly adherent to all parts of the fish, including snout, fins, and 

 tail. The ice glaze usually has bubbles or tubular holes in it, prob- 

 ably caused by the air dissolved in the water. Water heated to the 

 boiling point to drive off the air and then cooled off probably would 

 produce a better glaze. 



Tables 7, 8, and 9 give some idea of the amount of glaze put on 

 fish. In general, it varies from 2 to 7 per cent. Fish frozen singly 

 take a larger percentage of glaze than pan fish take, because there 

 is more surface to be glazed. Small fish, individually frozen, take 

 a larger percentage than large ones for the same reason. Soft, 

 smooth fish, like eels, mackerel, and lake trout, take a better and 

 heavier glaze than heavily scaled fish, like carp, drum, or red 

 snapper, because heavy scales act as insulators, preventing the water 

 from freezing quickly. Table 9 gives the amount of glaze on several 

 individual cakes of squid, showing that, though the average amount 

 of glaze is 2.5 per cent, that on the individual cakes varies from 0.8 to 

 3.9 per cent. It would be desirable for trade reasons to make cakes of 

 uniform weight and glaze, but so far this has never been accomplished 

 in practice. 



Table 7. — Glaze on blue pike, cakes frozen in pans 



Halibut usually are trimmed before they are glazed. The side fins 

 are chopped off with a large butcher knife or sharp hatchet, and the 

 nape usually is smoothed with a little trimming. As will be seen 

 in Table 9, the loss of weight in the trimming is about the same, on 

 the average, as the amount of glaze, so that an untrimmed, unglazed 

 halibut weighs about the same as a trimmed and glazed one. Fins 



