Dear Chingling,
I fully concur with what Peter has written, and I want to add something on
shrimp icing, from what I have observed on shrimp handling in many countries
around the world. Shrimp is a very expensive thing no matter where you are,
therefore nobody wants to pay ice for shrimp. At difference of other less
expensive fish that could be sold by the box, by number of pieces, etc.
shrimp is always weighed, without ice and drained from water.
This of course implies icing delays (particularly in aquaculture shrimp, but
also in capture shrimp) and shrimp brought to ambient temperatures (or
nearly) at some points in the chain. In the same way that shrimp cools very
quickly it warms up very quickly too. For instance some years ago during a
workshop on fresh fish handling we run in Puntarenas (Costa Rica) one of the
practical works was to measure the temperature of shrimp landed there and how
the temperature was increasing during the 1st and following sales after
landing. The shrimp arrived iced, but ice was taken out and it was washed and
drained in order to sell the shrimp. Drainage took so long that many shrimp
batches reached ambient temperature, this was composed by the fact that 1st
purchasers had to divide and re-sell the shrimp again. Perhaps this practice
has been improved by now in Puntarenas, but I witnessed similar situations in
many other places around the world.
In the other hand shrimp is resistant and continues alive long after it has
been caught, and this is a misleading indication for many people, including
fishermen and shrimp handlers. To be alive does not mean, even for fish, to
be healthy. Shrimp out of the water (natural seawater environment or shrimp
pond) is under stress, and this does not mean only discomfort for the shrimp,
but it means contamination, probably reduction in the shrimp immune system,
and definitely physical changes (that produce in some shrimp species
detectable weight changes). Therefore chilling is always advisable from the
time shrimp is taken out of its environment, chilling delays should be
avoided, and de-icing and warm ups reduced as much as possible.
The rush to ice the shrimp by the time it arrives to the final processing
plant can not improve shrimp quality or put time back. Icing should be
assessed always in conjunction with specific handling procedures. Ice it is
not an additive and should not be seen as such. Improvements due to the type
of ice (and icing) and/or in the heat transfer aspects are possible, however,
improvements in shrimp or fish should be assessed in practice, under actual
conditions. Otherwise we risk to be paying for keeping a quality or safety
condition that was already lost.
Actually by keeping constantly the temperature of the change of state (solid
to liquid), melting ice is a wonderful automatic, convenient, hygienic,
relatively cheap (in many places) and portable temperature control system. As
Harrison Ford express in the film "Mosquito Coast": "Ice(*)is Civilization!"
(*): he means artificial/mechanical ice. Ice is many things, but it is not
magic.
Kind regards.
Hector M. Lupin
FAO Consultant
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of P Howgate
Sent: 21 June 2007 17:41
To: Chingling Tanco; seafood@ucdavis.edu
Subject: Re: Chilled Storage of Fresh Fish (tuna)
Chingling
As Professor Labuza points out shrimp will cool within a few minutes in ice
slurry. The time will be a little longer when stowed in flake ice, but the
difference will not be of any technological significance. The question then
is the balance of advantages/disadvantages between the two processes. There
is no doubt in my mind that stowing in flake ice is to be preferred. I
described in my previous message the disadvantages of bulk and weight and of
the need to use more ice when using ice slurry and the possibility of
layering of water and ice, but I must emphasis in the case of shrimp the
penalty of leaching out flavourous compounds in the case of small products
such as shrimp. I have carried out experiments on the leaching of amino
acids, some of which are flavouring compounds themselves or flavour
potentiators, but can be considered as representative of other flavouring
chemicals such as nucleotides, and monitored the losses during processing.
The loss of flavour is more pronounced in the case of headless and is severe
in the case of peeled. In some cooked/peeled plants I looked at by the time
the cooked shrimps were held in ice slurry, cooled in ice slurry after
cooking, washed, and left standing in ice slurry between processing steps
there was hardly any amino acids and other flavouring chemical remaining and
the products were tasteless.
I would recommend that shrimp be iced in flake ice rather than crushed ice
as the large lumps in the latter can bruise the shells, which promotes
formation of black spot, and they should be iced in shallow boxes to avoid
compression damage, which again promotes formation of black spot. Cooling
and stowage in ice slurry prevents this damage, but I consider that this
benefit does not compensate for the disadvantages of this technique.
Peter Howgate
----- Original Message -----
From: "Chingling Tanco" <crt@mida-group.com>
To: "P Howgate" <phowgate@clara.co.uk>; "Dinesh Dhammika uduwana"
<dduduwana@hotmail.com>; <seafood@ucdavis.edu>
Sent: Tuesday, June 19, 2007 9:00 PM
Subject: Re: Chilled Storage of Fresh Fish (tuna)
> Hi Peter,
>
> What about if you were cooling shrimp - say 15-20 grams per piece HO
> or 10-20 grams headless. Because of the size of the shrimp, heat
> diffusion within the animal will not be much of an issue so does this
> make ice slurry more effective for cooling shrimp? What about storing
> shrimp overnight?
>
> Chingling Tanco
> Mida Trade Manila
>
>
> On 6/19/07 10:30 PM, "P Howgate" <phowgate@clara.co.uk> wrote:
>
>> Dinesh
>>
>> You need to differentiate between cooling fish in ice slurry and
>> storing fish in ice slurry.
>>
>> Ice slurry, because it is in complete contact with the surface of the
>> fish,
>> is a better heat transfer medium than is flake ice and could be the
>> preferred procedure for cooling large, warm fish such as tuna. However
>> flake
>> ice also makes good contact with the surface of the fish plus the melt
>> water
>> from the ice trickles over the fish making good contact with the fish.
>> Also
>> there comes a point in the cooling when surface heat transfer is not the
>> limiting factor for heat loss compared with heat diffusion within the
>> fish.
>> Altogether there is not likely to be a big difference in rates of cooling
>> between the 2 systems, but you would have to carry out comparative
>> experiments to determine the size of the difference in your
>> circumstances.
>> Ice slurries use more ice to cool a given mass of fish than using flake
>> ice
>> because the water in the slurry has to be cooled down as well as the fish
>> so
>> is more costly than using flake. It is important when cooling fish in ice
>> slurries that the mixture is stirred or the water phase recirculated.
>> When
>> the fish is added to the slurry some of the ice is melted and the
>> container
>> has layer of water and fish with the ice floating on top of it. If the
>> fish
>> has not cooled down completely this layer of fish and water will
>> equilibrate
>> at a temperature above 0degC and the ice floating on top will not cool it
>> down. This does not happen with fish stowed in ice; assuming there is an
>> adequate amount of ice all of the fish will cool down to ice temperature,
>> (actually a little below it, around -0.2degC, to be pedantic). Chilled
>> Seawater (CSW) systems - a slurry of ice with seawater- are often used on
>> pelagic trawlers to cool large catches of pelagic fish, but these systems
>> recirculate the water to ensure mixing. CSW is not the same as the
>> refrigerated brine storage used on larger tuna boats.
>>
>> Though ice slurry is effective in rapidly cooling fish when used
>> properly
>> it
>> is not a good medium or procedure for storing fish. Fish in ice slurry
>> takes
>> up more space, and weighs more than the same amount of fish in ice. These
>> are considerations for the space required to store the fish and for
>> transporting it. Suspension in water alters the appearance of the fish.
>> This
>> might not be a consideration for tuna destined for canning but is for
>> fish
>> going to retail sale. Depending how long the fish is stored in the ice
>> slurry the product can lose flavour due to leaching into the water, and
>> the
>> fish can absorb water. This might be favourable for the economics of
>> selling
>> the product, but not for eating quality.
>>
>> The Codex advice, and other texts on storage of fish, that fish
>> should
>> iced
>> in containers which allow for drainage is good advice and should be
>> followed. Fish in ice slurries are typically held in containers with a
>> drainage hole; just taking the bung out of the hole will allow for
>> drainage.
>>
>> Peter Howgate
>>
>> ----- Original Message -----
>> From: "Dinesh Dhammika uduwana" <dduduwana@hotmail.com>
>> To: <seafood@ucdavis.edu>
>> Sent: Saturday, June 16, 2007 12:07 PM
>> Subject: Chilled Storage of Fresh Fish (tuna)
>>
>>
>>> Dear All in Seafood List,
>>>
>>> Looking forward for the expert opinion on what is the best way of
>>> storage
>>> of fresh fish either only ice (flake Ice) or in a ice slurry composites
>>> of flake ice and water.
>>>
>>> code of hygienic practices for the fresh fish (Codex) says the water
>>> from
>>> melting ice should be drained to prevents bacteriological and chemical
>>> contamination!
>>>
>>> so if we stored in a ice slurry how can we facilitate drainage in
>>> stored in ice slurry!
>>>
>>> expecting expert comments soon.
>>>
>>> thanking you
>>>
>>> Dinesh Dhammika
>>> Ensis Fisheries Factory
>>>
>>> _________________________________________________________________
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>>>
>>
>>
>
>
>
>
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