Del Rocco
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Identification of Protein
I've recently been buying protein powder from the bulk foods section at the grocery, for health reasons, and had a curious thought.
How do I really know that the powder I'm buying at $8 a pound is protein, and not the $1/pound wheat flour that it looks (and tastes) exactly the same
as?
Is there a simple test to verify that this is indeed protein and not gluten?
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not_important
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Gluten is a mixture of proteins.
If you want to know if it is a high-protein mix and not just flour, you can try treating it like you do flour in gluten making. Beyond that
determining the amount of nitrogen in it would give you a little gaulatative data.
What does the labeling/ingredients-list say? Even if it is bulk, that should be posted on or near the bin.
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Mumbles
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I believe most of the containers just say "Whey Protein concentrate". Something like this is fairly standard. It matches up reasonably close to the
container I store one of my chemicals in.
Whey Protein Concentrate, Calcium Caseinate, L-Glutamine (2 grams per serving), Skim Colostrum, Lecithin, Branch Chain Amino Acids (BCAA's -
L-Isoleucine, L-Valine, L-Leucine), Oat Fiber, Magnesium Oxide, Potassium Chloride, Bromelain, Papain, Lactase, Green Tea Extract 50%, Grape Seed
Extract 95% OPC, OptiZinc, Ascorbic Acid (Vitamin C), Natural Vitamin E, Beta Carotene, Pyridoxine (B6), Selenium Methionine, ChromeMate (100 mcg per
serving), Folic Acid, Vitamin B12, Natural and Artificial Vanilla Flavor, Sucralose
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not_important
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OK, so milk proteins in effect. Meaning you want to tell the difference between what you bought and gluten.
Telling which proteins you have is more difficult. I believe that electrophoresis, including multiple steps that use variants such as isoelectric
focusing, is used to separate and identify the individual proteins. Not something that I have done.
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Mumbles
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We went over the process the other day in biochem, I can post some truncated notes if you'd like. As you already seem to be aware, it's a rather
expensive, and complicated proceedure. I do rather like the idea off using it in place of gluten in bread leavening or whatever it may be used for.
[Edited on 9-18-2007 by Mumbles]
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Ozone
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AGGHH! producing the ° symbol without the numlock on closes out your entire explorer and hoses your post .
OK, again:
The US gluten industry uses TKN (total Kjeldahl nitrogen), a *tedious* wet chemical digestion method and reports the result as protein as N.
Unfortunately, recent imports from a certain country test normally, but were, if fact, flour fortified with melamine/cyanuric acid.
To be more precise (but not quantitative, that will take to many typed words), you could:
1. dissolve as much as possible in water (or better, a buffer).
2. centrifuge or filter the mixture retaining the liquid phase.
3. Add trichloroacetic acid until the micture us roughly 10% and allow the protein to ppt.
4. if not ppt, there is probably very little protein in your sample (or you are failing to solublize it).
5. centrifuge this mess and discard the liquid. Resuspend the pellet in buffer and centrifuge again. Repeat this step 3 more times.
6. To the pellet add 0.5mL HCL 1:1, seal and put into oven at 100-120°C (whew) overnight.
7. Pipette an aliquot of the digest into (slowly) 1M NaHCO3 until CO2 liberation ceases. Check pH (7.5-9 is OK).
8. To this is added 100uL DANSYL chloride (20mM) in acetonitrile. The mixture is then heated at 80°C for 15 minutes.
9. repeat with water (blank) and say, BSA, casein, etc. (positive control). Examine the mixtured under LWUV. IF they fluoresce yellow (rather tahn
blue) you have amines. Then...
10. Run on HPLC with a complex gradient to separate and quantify the amino acids.
hmm. THen you could be sure...
There are other ways, but most quick tests are fooled by other amines.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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