Protein vs. crude protein?

[rayjay]

I'm hoping someone on this forum will be able to help me understand the differences between crude protein and protein when listed for something like a food.
A frozen food product has listed it's values as:
Crude Protein Min 5.80%
Crude Fat Min 0.60%
Crude Fiber Max 0.25%
Moisture Max 92.00%
Dry Protein % 72.50%

 

[HighlandReefer]

http://www.merriam-webster.com/medical/crude+protein

From this link:

Definition of CRUDE PROTEIN: the approximate amount of protein in foods that is calculated from the determined nitrogen content by multiplying by a factor (as 6.25 for many foods and 5.7 for wheat) derived from the average percentage of nitrogen in the food proteins and that may contain an appreciable error if the nitrogen is derived from nonprotein material or from a protein of unusual composition

 

[rayjay]

OK so I also used that site for the protein definition and from the two I've got the impression that crude protein is only nitrogenous based protein and protein is total protein including all protein in addition to the nitrogenous.
If that is correct, why report just crude protein on labels, or just protein, and why would both be used as in the site I have view for the frozen food?

 

[teesquare]

I think the impact of positve marketing, based on percieved "better" numbers - as compared to other competing brands is a the heart of the issue with many things.
Fish food is probably no exception.....

T

 

[DarkXerox]

I think it also has to do with the dry weight of the protein vs the dry weight of the other components given their listed ratios. On a percentage scale (likely volume/volume), the protein is in the range of 87% of the total dry items listed. Assuming fats and fiber have higher densities, this somewhat makes sense that the protein would be 72.5% of the dry mass.

 

[teesquare]

Hmmm... well - my question would be: If we are looking at frozen foods, are there any ingredients that are ever "dry"?
I would think that they take the food ingredients from the source (?) and then prep them, and even add some water for packaging convenience ( and possibly the "thumb on the scale effect!) then - freeze them.

But - I do not *know* how they are made...Anyone have firsthand knowledge?
T

 

[DarkXerox]

I'm sure they use some sort of drying oven, lipid extraction, etc. to find out. Even "whole" foods like mysis list these component ratios. Most foods that are mixtures probably use both dry and wet components. Whereas others could just be lots of shellfish, fish, crustaceans, etc put into a blender and mixed with a binder and preservative.

 

[teesquare]

Yeah - I see...Wonder if a manufacturer could wander in here to take questions directly - or would that need to be done on a sponsor forum...?