By clarifying butter, e.g. by melting butter and filtering it, we rid ourselves of most of the protein in the butter, and are left with mostly fat. However, the separation of protein and fat is not complete. Some people cannot eat milk proteins due to allergic reactions, and cannot therefore use unrefined butter in their cooking.

Is there a simple "home-kitchen" procedure to test whether the filtration sufficiently removed the milk proteins? Any proteins in the ghee can be precipitated by adding acetic acid, but this is not specific to milk proteins.

Does anyone have any ideas?

  • $\begingroup$ Is the thinking here that removal of whey protein will also help remove lactose? $\endgroup$
    – Beerhunter
    Jul 16 '15 at 22:54
  • $\begingroup$ No, the sugars are not relevant to those allergic to milk proteins. $\endgroup$
    – Yoda
    Jul 16 '15 at 23:48

A classic test for protein is Biuret solution, using readily available reagents: sodium hydroxide, copper sulfate and potassium sodium tartrate (Rochelle salt). The test is not specific for milk protein, but what other protein would be in pure butter?

Use caution with the chemicals -- the first listed is quite caustic, and the second is poisonous. BTW, save some leftover Rochelle salt if you'd like to make a piezoelectric crystal.

  • $\begingroup$ Are there compunds readily available that binds to milk proteins, while not affecting the taste of the clarified butter? Or that binds to every type of protein. If all protein is lost, then the butter would be safe for those with allergies. $\endgroup$
    – Yoda
    Jul 16 '15 at 23:51
  • 1
    $\begingroup$ I am not sure that the limit of detection of the Biuret solution is low enough to reliably indicate the absence of an allergen. $\endgroup$
    – Curt F.
    Jul 17 '15 at 7:26
  • 1
    $\begingroup$ Biuret is only good down to ~1 g/dL. Coomassie blue is commonly used for protein concentrations 2-3 orders of magnitude lower (mg/dL). Even then, I don't know that I'd risk it. $\endgroup$
    – Gossar
    Oct 27 '17 at 10:00
  • $\begingroup$ @Gossar, point well taken: if the problem that milk protein causes is mild indigestion, it might be worthwhile to test... but if there's chance of a severe allergic reaction, i.e. anaphylactic shock, this would not be a good home experiment! And thanks for mentioning the Bradford (Coomasie blue) test. $\endgroup$ Oct 27 '17 at 14:48

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