METHODS OF FREEZING FISH.

Nelson Evening Mail, Volume LIV, 23 March 1921, Page 4

METHODS OF FREEZING FISH.

- ..v Till-: Fish I’IVS. ‘fVi'U ion (TmmVii loc in'] the lirilish Fund I nve.-uigo t ion Hoardj has issued an interim report ill view I ni (lie need For Improvement in ilmi methods oi' handling fish in the Old: Fount ry. This la 'port is confined as. elosely a- may In* i.n a discussion of ; the |>mc<’dl;iv lies! suited for the pro-' s<■ fv;i 1 mu of common fish sin-h as herrings nr sprats during :t glut, so Hint 1 they may he held in store until the, market.- is capable of absorbing lhem,i or 1o ket'p a canning Factory in steady! employment. in ii the suitability of! various methods ol' Freezing For deal-, inn with gluts of hdi such as herring i> discussed, and the process of freezin:; in brine is recommended on the '■Tonltd i hat it gives the best preset - - 1 ■ ration and is the most rapid. The only apparatus repaired is an insulated tank filled with brine and connected with a refrigerating plant, so thatthe temperature of the brine may be ( reduced to and maintained at the repaired level, Uoughly. the’ rime re-j paired to Freeze fish in brine- is only, une-ien ill to one-fifteenth of that, needed to freeze in air. and t he rapid i Freezing ensures the he<( possible pre-| serration of the tissues. The texture; of the tlesli is not destroyed by the| formation of large ire-crystals as hap-; pens in air Freezing. I’Tsh properly | Frozen in Inane ran ho kept tit cold; store For many months without de-{ terinratiou ot appearance or flavour., and, . notwithstanding the immersion! in cold brine during freezing;, the fish i eontract.no taste of salt; and when | (hawed they are in practically the same condition as they were before, freezing. Kish hrino-frozen and stor-1 ed are tillable also for processes other, than canning, stieh as smoking. The central Fart of chief importance tit any theory of the freezing ot fish is tit at with sufficiently rapid Freezing tito relatioMs, both chemical and phy-. steal, of the constituents are either preserved unchanged. or. it th,\\ he changed, iho altered relation.-, are sue it as to he exactly reversed when the temperature rises attain —when the tissues, that is, are thawed. To preserve the tissues completely the heat must he extracted and the tissues Frozen as rapidly as possible. It may be assorted that very rapid fteezing w ill preserve texture. Flavour is not so simple a mailer, ft is,determined, so Far as is known, by the presence of chemical substances the nature and orient of which are entirely unknown. Ami only a guess can he made at what “freshness’’ means. If. indi-(-..,ie- a period in iho changing chemi■id system and probably one as nearly as possible co-incident with the state win'll rip or mortis has just given way lo suppleness, renewed by the resolution of the doited substance of Lite muscle fibres, the hulk oi the edible parts of fish consisting of the ■muscles which more the body of the Mtimal. In practice, with the exception of fish caught in the great lakes of North America in winterim! frozen practically when alive, fish comes For Freezing 1 , long tiller rigor ■mortis has disappeared, and tile object oF freezing may he defined as the holding of the flesh in (he particular chemical and physical state to which its nroviotis history since death has brought' it. The evidence review'd ill the report points to the eonelusion that, the more rapidly iho fish is frozen ihe more likely is ibis ptesorva(ton to he complete. Tins procedure, .if cold brine he used, will destroy a- large proportion of the bacteria infecting the fish. The frozen fish, if they are to he kept in store ;or any length of time, should be kept at a uniform and low temperature and stored in boxes closely stacked so afl to lessen ;e Far as possible free access of air. As some confusion exists as to the reason For the use, of brine in place of water as a cooling medium, it may he well to state that the salt is added, not for the purpose of preserving or pickling the surface of the fish huf. in order i:o lower the freezing'’point of the water so that a low temperature may he used and rapid freezing -secured. The use of strong brine has been objected' to on the .rrottml that the salt will cling to and -wen penetrate the surface of the fish. Experiment, however, proves that fish can he frozen in strong brine without retaining enough salt, co ho detectable hv taste, provided-the temperature of the brine is cold enough. Broadly speaking, two industrial processes are at. the moment- available by which fish may he frozen rapidly namely, .sharp freezing m air and freezum hv Immersion in cold brute. it,.,;; 1« ..!.'■ e- «* «, likely to suffer excessive drying during freezing. Considered as a factory practice, freezing in brine is rapid ~nd therefore adapted specially to gluts. Herring, for instance, can bo completely frozen in 15 minutes, whilst .hr freezing needs at least five hours. !fc is true that the fish cannot he satsfaetorilv glazed if the process is to ccmain simple, but good keeping remits are given by the unglazed fish if the simple precaution is taken of •lacking them as closely as possible. \nd a point of practical importance s the fact that fish frozen m brine I dtow less loss of weigh! due to dry- ; j,g that do lish frozen in utr. 1 rofiahly, as already indicated, the chief, advantage of brine freezing over any form of air Freezing lies in f!l ° hetler preservation of the texture of the tissues. It is doubtful whether .in irae-tioo freezing in air can he made sufficiently rapid io prevent the separating out Of water in the- muscles. With brine freezing, on the othoi hand, the rate of freezing can usually .bo made great enough to prevent anr' ; exudation of water from the muscle fibres. The result is that the texture of brine-frozen fish on thaw-

ihj,i; is praeficnll.v Unit ni iresh fish, u Ij l li Ihe ihsiies of air i’m/.en lull ar.- api io be dr;, and U""H> train loss oi water. Good pre-a-rva Imu and rapidity in pram h-c I hereinre eoinnie:ld I; r i;; 1 ■ Iree’/ailg io ibe commitlee as (lit' process be--l sidled tor preservin',!, large (pnniilies of fish of ihe kind in question.