To the "ice needed to chill fish" discussion gang,
This is an interesting discussion of "rules of thumb" and the
"thermodynamics" of how to figure out how much ice a fisherman needs to
"properly?" chill fish. But please remember, the bottom line often is
determined by the question of "who is paying for the ice?" If the fish plant
is providing the ice "free" the fisherman will want to take all they can
get. If fisherman are paying for the ice they will try to keep it at a
minimum. But if the ice is limited in supply, then there is a strong desire,
both by fishermen and fish plants, to be accurate in figuring out the real
quantity needed to meet some temperature specification.
Ken Hilderbrand
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu]On
Behalf Of Andrew Strak
Sent: Sunday, July 16, 2000 8:37 AM
To: jperalta@iloilo.net; seafood@ucdavis.edu
Subject: Re: Amount of Ice to Chill Fish
And usually the industry goes by the rule of thumb that works quite well.
For refrigerated fish holds in the Northern hemisphere and the average
length of trips 7-10 days it can be 1 part of ice per 2 parts of fish with
more ice being added in summer or when the trip is longer. Certainly, the
ice distribution around the fish is also very important and that may depend
on the type of ice being used. It does not only cool the fish but also
keeps it apart while allowing for oxygen to penetrate. A direct fish to fish
contact sometimes leads to undesirable marks and skin discoloration; besides
some anaerobic spoilage may lead to bilgy odours. Moreover, melting of ice
is perceived as beneficial to the product since it moistens the skin.
Andrew Strak
----- Original Message -----
From: "Ted Labuza" <tplabuza@tc.umn.edu>
To: <jperalta@iloilo.net>; <seafood@ucdavis.edu>
Sent: Sunday, July 16, 2000 12:11 PM
Subject: Re: Amount of Ice to Chill Fish
> Dr Perlata has a good idea (below) I will take it one more step
>
> We can create a ice to fish ratio
>
> mi/mf = (t1 - 0)/Lf = Tf/80
>
> This says the Kg ice needed per Kg fish (or Lb per lb for that mater) is
simply
> 80 divided by the fish temperature Thus
>
> for cold water where Tf = 5 the ratio is 5/80 = 0.06
>
> for moderate water temp Tf = 20 the ratio is ~ 0.25
>
> for warm water eg in the Phillipines Tf = 35 ratio is ~ 0.44
>
> using a cp of one also gives a 20% overcompensation which is in the right
> direction.
>
> The problem of couse is with a low ratio one may not get the ice throughly
mixed
> with the fish
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
> Responding to the message of <3971922A.9218B6BA@iloilo.net>
> from jperalta@iloilo.net:
> >
> > Dear all:
> >
> > Here is an alternative.
> >
> > And may I use SI units?
> >
> > Assuming no heat losses, and ice temp is 0 C (normal ice temp); and that
> > the final temp of fish sought is not lower than 0 C.
> >
> > Heat given off by the fish = Heat absorbed by melting ice
> >
> > mf cp (t1 - 0) = mi Lf
> >
> > where
> > mf is the mass of fish in kg;
> >
> > cp is the specific heat of fish; I agree with parameters stated earlier
> > but we could simplify further and make it 1(unity); kcal/kg-C
> >
> > t1 is the initial temp of the fish; C
> >
> > Lf is the latent heat of fusion of water; 80 kcal/kg; lastly
> >
> > m1 is the amount of ice; kg, (which is the one sought for), and could
> > easily be calculated.
> >
> > This calculation is a fast estimate of the base ice requirements.. We
> > normally use more than this value to compensate for transport heat
> > losses and other losses/factors.
> >
> > ----------
> >
> > Another alternative is to use a "rule of thumb"; the ratio of 1 part
> > ice to 2 parts fish. This seems to also satisfy the aforementioned
> > calculations, and also compensating for the other heat lossess.
> >
> > Then of course, this assumes that the initial fish temp to be at normal
> > water temp.; which is around 25 C.
> >
> > I hope this helps.
> >
> >
> > Best regards,
> >
> > Jose
> >
> >
> >
> > --
> > -----------------------
> > Jose P. Peralta, Ph. D.
> > Professor/Food Engineer
> > Inst. of Fish Processing Technology
> > College of Fisheries, Univ of the Phil Visayas
> > 5023 Miag-ao, Iloilo, Philippines
> > Tel (63 33) 315 8289
> > FX (63 33) 315 8289, 315 8353
> > Cell (0917) 302 1282
> > EMail jperalta@loilo.net
> > ------------------------
> >
> >
> > .
>
>
> Dr Ted Labuza tplabuza@tc.umn.edu
> Prof. of Food Science Dept. of Food Science & Nutrition 136 ABLMS U of
Minn St
> Paul, MN 55108 Voice 612-624-9701 Fax 612-625-5272 home fax 651-483-3302
> cellemail 6126697885@mobile.att.net
> http://fscn.che.umn.edu/Ted_Labuza/tpl.html
> "SURFING THE WAVES OF CYBERSPACE"
> ___
> |กก|
> | \|
> |__| "The attitude of an engineer must be different than
> | that of a mathematician. The engineer is concerned with
> ---|---- truth, not mere consistency." Biot
> / \
> |___/__/\_____/
> \ /\ /\ /\/\/\
> \ /\ / \/ \ /\/
> "Before I came here I was confused about this subject. Having listened
to your
> lecture I am still confused But on a higher level."- E. Fermi
>
>
This archive was generated by hypermail 2b29 : Sun Jul 16 2000 - 21:04:56 PDT