Sciencemadness Discussion Board

Aspartame Isolation

hodges - 10-8-2009 at 13:37

According to Wikipedia, aspartame is 180 times sweeter than sugar. I have here a brand of artificial sweetener that lists its ingredients as "maltodextrin, aspartame". This sweetener advertises that it "measures like sugar". It is very fluffy; 4 ounces of this product occupy a space that looks to be close to a quart. It apparently has a lot of air in it; it fizzes upon touching the tongue.Given that aspartame is 180 times sweeter than sugar, and the fact that the product appears to be 1/8 the density of sugar, I'm thinking it is probably about 95% relatively tasteless maltodextrin and 5% aspartame. I wonder if it would be possible to separate these?

This is more "for fun" than anything. I know it is easy enough to buy pure aspartame on E-Bay. I just think it would be fun to have a sweetener so strong that a piece the size of a couple grains of salt would sweeten (say) a whole cup of water. I know of one interesting experiment that involves making a pleasant smell using aspartame and a vitamin tablet, but this does not require pure aspartame anyway.

Hodges

chemoleo - 10-8-2009 at 14:35

You could make use of the free carboxy and free amine, by forming a salt with either NaOH etc or HCl etc.

This should crystallise more readily, and could be seperated away.
Alternativley, you could find a solvent that keeps the maltodextrin in solution but otherwise precipitates the hydrochloride salt of aspartame. I.e. dissolve the sweetener in acetone, see if it all goes into solution, and then gas it with dry HCl or add H2SO4 to precipitate the aspartame salt...

hodges - 13-8-2009 at 18:00

I tried a couple of experiments this evening.

Isolating apartame was not successful. I added about 1g of sweetener to about 3ml of water. I added 3M HCl dropwise. No precipitate formed. Also tried instead adding a KOH pellet. The solution turned slightly green near the KOH pellet at first, but this color went away on shaking and there was no precipitate. Tried dissolving the sweetener in acetone - it appears completely insoluable.

Making trace amounts of good-smelling benzaldehyde was successful. I dissolved about 1g of sweetener in about 20ml of 3% H2O2. To this I added a crystal of CuSO4 and about 1ml of approximately 3M acid. Finally, I dropped in a Vitamin C tablet. The result was a definite cherry smell in less than a minute. When using HCl for the acid, there was also a biting smell that went with it (perhaps just HCl or impurities in the acid). When using H2SO4 there was just the cherry smell. I'm not claiming this is an efficient way to produce benzaldehyde. However, it is always interesting in me when a reaction appears to produce "something from nothing". Starting with nearly odorless reagents, and with very little work, you end up with a pleasant smell. This could be a good demo as well, since there is nothing too dangerous used.

Hodges

Sedit - 13-8-2009 at 18:13

That was my thoughts as well when I first performed this same exact experiment hodges. No real practical value as of yet but still would make a great childs science far project sinces its a mix and smell type of project and the person could have every solution next to each other then mix one at a time until the cherry smell appears. For a demo one could go into how the addition of ascorbic acid could alter the sence of taste and smell on consumer products containing artificial sweetners and things such as this producing a pretty nice writeup that would have backup from recent scientific papers.

not_important - 13-8-2009 at 23:57

Because it has a carboxy and amine group, aspartame is an internal salt and has low solubility in non-protic solvents and even alcohols are rather poor solvents for it. It's also not that soluble in water, something like 1% y weight at room temperature.

As you've already seen, adding simple acids or bases does not decrease the solubility to any significant degree, many acids actually increase aspartame's solubility in water. Strong base is likely to result in the hydrolysis of the methyl ester.

The formation of enough benzaldehyde to smell does look to be a nice demo. I.m a little surprised the amide is chopped so readily, I assume that the H-N gets oxidised even in an amide form. It is likely that the copper complexes with the aspartame to form the active catalyst.

And the word is 'cents' if it's about money, 'scents' if it's about aroma, and 'sense' if it's about perceiving - sight, smell, taste - or being logical - making sense.



JohnWW - 14-8-2009 at 01:14

Quote: Originally posted by not_important  
Because it has a carboxy and amine group, aspartame is an internal salt and has low solubility in non-protic solvents and even alcohols are rather poor solvents for it. It's also not that soluble in water, something like 1% by weight at room temperature.
A zwitterion, which in fact amino-acids usually are in polar solvents. This being the case, it would probably be isolable by electrophoresis (a form of chromatography in which an electric potential is applied between the ends of the medium used). This is commonly used in biochemistry for analysis and separation of amino-acids. Each such substance has an iso-electric point in terms of voltage, at which it remains stationary. See:
http://en.wikipedia.org/wiki/Electrophoresis
http://en.wikipedia.org/wiki/Gel_electrophoresis
http://www3.interscience.wiley.com/journal/10008330/home
(someone please download this)
http://www.aesociety.org/


[Edited on 15-8-09 by JohnWW]

Sedit - 14-8-2009 at 06:38

Here is the paper discribing the reaction in question'

Attachment: BnO.pdf (282kB)
This file has been downloaded 533 times

Ozone - 14-8-2009 at 12:30

Ion exhange will do. IN this case, the peptide will be retained, the maltodextrin/glucose rinsed out with water and the peptide eluted.

This can be done with a large atmospheric column as well. This is reusable and robust.

see (HPLC, but the priciple is the same):

http://www.ncbi.nlm.nih.gov/pubmed/2980785

Oh yes, thanks, Sedit, for the nice paper.

Cheers,

O3

[Edited on 14-8-2009 by Ozone]

Sedit - 14-8-2009 at 18:06

You welcome,
Its been sometime since I read that paper but I wounder if any of you real chemist(IE not me:D) Have any suggestions on how one could increase the conversion to benzaldahyde from Aspartame. IIRC the yeilds where pretty crappy and somewhere along the lines of like 2-3% but still enough to produce a nice smell from when done right.

Ozone - 14-8-2009 at 21:40

I think that the proposed mechanism looks OK, but the whole thing appears to be a side reaction in competition with several others that are likely to be faster in this system. They did look for benzoic acid, which I thought would be indicative of oxidation of the product (thus limiting the yields), but found little or none. This seems a bit strange because the common oxidant (thought to be HO.) will do that. Perhaps it has some thing to do with the enormous excess of (it appears more easily oxidized) substrate at any given time.

Interesting,

O3