Responding to the message of
<NDBBIAMAALMAOKEAPCPPGEDFCCAA.kurt_jacobsen@hnfoods.com>
from <kurt_jacobsen@hnfoods.com>:
>
> Dear Members:
>
> When Is It Cold Enough ?
>
> I'm interested in learning more about freezing and cold storage temperatures
> for oily types of fish such as mackerels.
>
> I understand the basic concepts behind freezing product rapidly as it
> relates to the ice crystal formation and cell structure of the meat, and
> that colder is better for both freezing and cold storage temperatures.
The general explaination that ice pierces the cells is wrong It is the osmotic
difference between the cell and the external fluid that esukts in tissue damage,
diffusion of water to the outside and drip loss. Fast freezing is best but the
advantage is lost if the food is stored at higher temperatures.
>
> My questions are:
>
> A) At what temperature as you go colder, (-30C, -40C, -50C, -60C....?), is
> there no longer a benefit to product quality, (texture, color, flavor, etc
> after thawing), or is there such a temperature point? (ie: is there a
> breakeven point or law of diminishing returns at which going any colder
> would not add any improvement to the quality of the product, and therefore,
> investing more dollars in refrigeration equipment to go colder for initial
> freezing and/or cold storage would not be necessary).
If you go below -50C you can induce the oxidation of fats There was work
published on this for frozen hams by the Danish Meat Research Labs in Roskilde
at least 20 years ago.
>
> B) If you blast freeze these products at say -40C, but most cold storages
> maintain a temperature of -20C, what impact does the temperature differences
> have on the quality of the product?
For some foods like strawberries, an 10 C difference at frozen temperatures
results in a forty fold (Q10) difference in shelf life For fatty fish the Q10
is about 3 to 3.4 fold.
>
> Regards,
> Kurt Jacobsen
>
>
> .
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"
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|__| "The attitude of an engineer must be different than
| that of a mathematician. The engineer is concerned with
---|---- truth, not mere consistency." Biot
/ \
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\ /\ / \/ \ /\/
"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
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