Dear Steve
Depends on what your enquirer means by 'denaturation'. Technically
denaturation is the unfolding of the tertiary structure of a protein by some
agent such as heating, marked change in pH, effect of some chemicals. The
unfolding leads to various changes including, for example loss of enzymic
activity, loss of water binding. Proteins differ with regard to the
temperature that results in denaturation and as muscle tissue is a mixture
of proteins there will be a range of temperatures over which salmon muscle
proteins will denature, but the situation can be simplified by grouping the
proteins. There is an experimental problem of how to measure the temperature
at which the protein denatures and a method commonly used is differential
scanning calorimetry. Using this method the denaturation temperatures of
proteins in Atlantic salmon have been measured (Ofstad, R. et al., 1996,
Liquid loss as effected by post mortem ultrastructural changes in fish
muscle: cod (Gadus morhua) and salmon(Salmo salar), Journal of the Science
of Food and Agriculture, 71, 301-312). The results show that myosin, the
major structural protein in muscle denatures in the range 45-55degC, actin,
the other major structural protein at 74degC and the sarcoplasmic proteins
between these temperatures.
I have a feeling your enquirer is really asking for the temperature at which
salmon flesh cooks so that he/she can keep below this temperature during the
smoking process and is equating cooking with denaturation of protein. The
observable criterion of cooking in these circumstances is liquor exuding
from the fillet, that is, cook liquor, and loss of integrity of the fillet
so that it gapes or even falls apart. The loss of liquor can be equated to
denaturation of structural and sarcoplasmic protein reducing the water
binding property, but the disintegration of the muscle is more related to
the conversion of collagen to gelatin with associated loss of strength of
the connective tissue. This is the reaction which results in flaking of fish
on cooking. I do not have a value of the temperature for this conversion for
salmon, but data for some species of fish will be in Sikorski, Z.E. et al.,
1984, The role of collagen in the quality and processing of fish, Crit Rev
Food Sci Nutr. 20(4), 301-343. This phenomenon of breaking up of the fillet
is well known to fish smokers preparing hot smoked products. The trick is to
raise the temperature in the kiln as the fish dries because the collagen
becomes more resistant to degradation as the water content drops.
Peter Howgate
----- Original Message -----
From: <sharbell@u.washington.edu>
To: <seafood@ucdavis.edu>
Sent: Tuesday, November 21, 2006 6:28 PM
Subject: Denaturation Temperature for Salmon
>
> Had a request from a fish smoker for information on the denaturation
> temperature for salmon. Does anyone have that information? Thanks
>
> Steve Harbell
> Marine Resources Agent, County Director
> WSU Extension, Grays Harbor and Pacific Counties
> Washington Sea Grant
> Tel. (360) 875-9331
> P. O. Box 88, South Bend, WA 98586
>
>
>
>
>
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