rannyfash
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Homemade Protein Powder - protein assaying needed
I can understand if a few might not consider this as chemistry and more of a cooking technique.
recently I've been working on my own soylent recipes, soylent being a drink that contains everything needed to survive, Link here to my recipe (do not attempt to make this, it tastes rank, I'm working on getting it to taste nicer) the most expensive ingredient is
protein powder and I could not understand why it was so expensive, I could only find limited information on how it was made, it might be obvious to
some but I am very impressed it can be made like cheese, in short the soluble proteins were aqueously extracted and precipitated by lowering the pH to
its isoelectric point.
Starting with 100g of raw dried split peas, the peas were soaked overnight and macerated, the volume of water used was not recorded but enough is
needed to create a roughly viscous slurry, this was then filtered through cheesecloth by gravity to avoid leaks then squeezing was used to drain the
rest of the liquid, after leaving the collected liquid undisturbed for an hour it was decanted leaving starch residue at the bottom, the liquid was
heated in a pan, when the liquid was just starting to boil, the pan was removed from heat and 2 table spoons of vinegar was added with brief stirring,
after leaving for 20 minutes for the protein to flocculate, the mixture was gravity filtered to obtain a low density rubbery chunk, this was dried in
an oven and ground to obtain 20.15g of a free flowing powder.
This powder based on 100% extraction should be 24.6g protein and 1.2g of fat according to the nutritional data, as the non/less polar compounds flocculate including the fats, because of this assuming the yield of protein to be 19g and that
dried split peas can be bought cheapest in bulk at 90 pence a kilo from this website, on average the cost of protein excluding energy costs would work out as £4.74 per kilo of protein experimentally and £3.66 a kilo
of protein if a 100% yield was obtained, compared to the cheapest commercial pea protein at MyProtein for £7.60 (since removing the 2.5kg option this is now £10.99 per kilo), my estimates on yield are only calculations based on
nutritional estimates, I understand its flawed, which is why a protein assay is needed, Id also like to add that the commercial protein has a nasty
taste that has not been reproduced in my own experiments.
Although what I've done isn't original I've shared what knowledge I have on this subject, if any of you are body-builders or you're on a vegan diet I
hope you find it a useful supplement and I hope someone can share with me the knowledge on protein assaying, I've read a little and it seems a little
bit costly for a hobbyist such as myself to send off a sample to a company to analyse the overall protein content.
[Edited on 31-8-2014 by rannyfash]
[Edited on 31-8-2014 by rannyfash]
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phlogiston
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The biuret test is simple and should give reasonable results. Because you have very large amounts of protein, you don't need a very sensitive method.
Ideally, you would want to use a spectrofotometer to measure the light absorbance at a specific wavelength, but you can probably get a pretty good
estimate by eye if you make a series of calibration solutions to compare with.
Other popular protein assays are the Bradford assay and the BCA method.
Both are very simple to perform, but some of the reagents may be harder to acquire.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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rannyfash
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I had gone over those techniques but dissolving the powder in liquid just obtains a cloudy solution, my immediate thought was to break the protein
into smaller chains with acid or alkali but that would destroy some of the amino acids, just realised that even if the amino acids are converted into
other compounds they will most likely still be ligands, in which case it should still be all right, give me a week and ill be back with data, thanks
for the help
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phlogiston
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That is most likely because the proteins are denatured, which occured when you boiled/precipitate them (they unfold, exposing their hydrophobic
surfaces on the outside which causes them to aggregate and precipitate).
Two ideas:
1. Try dissolving it in an 8M urea solution. That often works (apply some heat to help the refolding/solubilization) and is compatible with the
bradford assay. I have not checked if it is compatible with other methods.
2. Alternatively, measure total nitrogen content. That should closely correlated with the protein+amino acid content.
BTW, most of the free amino acids survive alkaline or acid hydrolysis conditions (this is a common first step in determining the amino acid
composition of proteins), but then you can't use a protein assay anymore (they only detect peptides, not free amino acids).
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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rannyfash
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thanks for the info, exactly the protein is denatured and needs solubilizing, id prefer not to use ammonia, using biuret reagent (my preferred choice
for its simplicity) it would give a dark blue tetraamine complex with copper which would make it hard to distinguish without a spectrometer, i think
im going to heat a small sample with acid until it looks clear and use biuret reagent, why don't amino acids form copper complexes? and i read this from the university of oxford, are the amino acid degradations negligible?
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rannyfash
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scrap that, kjeldahl method looks very enticing, I'll post the data regardless of which I choose
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