Does cysteine break down in filtered water? Should this made more acidic?

If I mix cysteine powder in juice (something acidic maybe), does it remain at cysteine? It seems that it can oxidize into cystine and lose some of its qualities.

  • $\begingroup$ I see an article titled Cysteine stability in aqueous amino acid solutions. Looks like that might do the trick. It goes on to say Optimal conditions for cysteine stabilization in aqueous solutions of amino acids, available for parenteral protein feeding, were found. It is in Rushan; maybe I can use a translator. I'm having trouble finding where to download the article. I see only the abstract. ncbi.nlm.nih.gov/pubmed/6431404 $\endgroup$ – jcalfee314 Jun 15 '13 at 16:56

I wouldn't worry at all about the oxidative dimerization of cysteine to cystine when you consume freshly prepared solutions.

In the lab, you'd use oxidants, such as $\ce{FeCl3}$ (in the presence of air) or hydrogen peroxide to achieve this reaction; both of which you're not likely to add to your amino acid diet!

As far as the article which you mentioned is concerned: The stabilization methods in question will only be relevant to maintain the composition of prefabricated and sterile-packed solutions over a long period of time.

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