Tímarit Verkfræðingafélags Íslands - 01.12.1967, Blaðsíða 77

TlMARIT VPl 1967
75
unni og verður það ekki gert hér, nema að mjög
litlu leyti.
Ef nota á slíkan fisk sem hráefni til frekari
vinnslu, verður nær óhjákvæmilegt að nota upp-
þíðingarvélar. Uppþíðing í lofti eingöngu er alltof
seinvirk, þegar þíða á upp stórar, þykkar togara-
blokkir. Slíkar uppþíðingarvélar eru á markaðn-
um, en eru að vísu dýrar. Uppþíðing er ýmist
með vatni, rökum loftblæstri eða með rafmagni.
Þegar notað er rakt loft eða vatn, er hitinn hafð-
ur um 20 °C og uppþíðingartími er um 4 klst.
miðað við 12 sm togarablokkir. Hátíðniuppþíð-
ingarvél, sem notar háspenntan (5.000 volt) há-
tíðni (50 millj. sveiflur/sek) rafstraum, þíðir
sömu blokk á um það bil 1 klst.
Áætlaður stofnkostnaður við eina slíka vél
(vatnsúðun) er nál. kr. 2.000.000,00 miðað við
íslenzkar aðstæður (Tafla 6), og er þá gert ráð
fyrir 25% aðflutningsgjöldum, ásamt söluskatti.
Reksturskostnaður af slíkri vél er hér áætlaður
kr. 558,00 á tonn af uppþíddum fiski, og er þá
gert ráð fyrir 150 daga vinnslu og 8 stunda
vinnudegi, enda ekki gert ráð fyrir að vélin yrði
notuð, þegar nóg annað hráefni berst að (Tafla
7).
Sparnaður við slíkt hráefni er nokkur, meðal
annars vegna betri nýtingar vinnuafls, minnkaðr-
ar yfirvinnu, sem á íslandi er dýr, miðað við
nágrannalöndin, o.fl.
Veigamesta atriðið í því, hvort fiskiðnaður-
inn getur notað heilfrystan, uppþiddan fisk sem
hráefni, er kostnaðarverð hráefnisins til fisk-
vinnslustöðvanna, en um það skal ekki fjallað
hér, enda er frysting í verksmiðjuskipum undir
öðrum lið á þessari ráðstefnu.
Summary
The paper deals with the handhng of wet fish
and various methods of enhancing storage life
from time of catching till processing. Whichever
the processing method is the object of wet fish
preservation will be to retard spoilage and slow
down any changes in the fish, whether chemical,
physical or physical chemical, the causes of
which are mainly bacteria, enzymes and mech-
anical handling. The phenomena of rigor mortis
is discussed and described.
The effect of exercise prior to bleeding is to
reduce keeping quality. Blood in muscle caused
by improper bleeding causes dark fish fillets of
reduced commercial value. The object of gutting
is to remove bacteria and digestive enzymes
which attack the muscle. Cod fish caught hy
dayboats during winter season are normally not
gutted at sea in Iceland as it is felt that the
labour involved and inconvenience to the crew
do not justify this operation or possible quality
improvement. This fish should, however, be
properly chilled, no matter how short the
journey.
There have been rather great alterations in
fishing technique used for providing raw
materials for fish processing in Iceland. Line
boats, net boats, purse seiners, trawlers etc. have
come and gone in cycles. During the last few
years emphasis has been laid on purse seiners,
medium sized fishing crafts primarily designed
for catching herring. These boats have gone
farther and farther away from Iceland for fish-
ing, i.e. to Jan Mayen, Faroe Islands, Shetland
Islands etc. The consequence has been lack of
fish for the processing plants, all except herring
meal factories.
Keeping quality of fish in ice is reviewed as
well as the importance of chilling, the technique
and object of icing, the design of fish holds and
auxiliary equipment, the value of insulation, re-
frigeration etc. The amount of ice neccessarry to
absorb heat load in various fish holds is computed
and reported.
The method of preserving fish in refrigerated
sea water is described. This method, which is
used by fishing boats, canneries and shore in-
stillations on the Pacific Coast of the U.S.A. and
Canada, has not been generally adopted else-
where, although several isolated users are re-
ported, and experimental work has been carried
out at several experimental stations. A pilot
plant system was installed in Iceland in 1956
and one large freezing plant has now installed
a RSW system. Icelandic lobster tails (scampi)
are often kept temporarily in iced sea water, and
one herring boat has RSW system for 80 tons
of fish. Indeed it is thought that this system
might be of value to keep herring sufficiently
long to enable the boats to deliver the catch to
salting and freezing stations instead of to re-
duction plants, as brailing and pumping herring
from purse seines have become very fast and
efficient, making proper icing difficult. In order
to keep up with it too large quantities of ice
would have to be moved in too short a time.
In 1964 a tanker was first used to bring herr-
ing from boats at sea to shore plants, using
pumps to transfer fish from fishing boats to
carrier. Other tankers have since been added to
the fleet for the same task. In order to make
this raw material available for freezing and