May be beating a dead horse, but found this on MoreBeer's online store - their Burton Salts may or may not contain papain. They don't list it as an ingredient.
Also known as brewing salts, it is a mixture of Gypsum, Potassium Chloride and Epsom Salt. 1 tsp adds 1119 ppm per 5 gallons. For Pale Ales in the Burton on Trent style. Burton salts can come in either crystal or powdered form. We ship what is available at the time your order is placed.
30g per 5 gallons will provide:
266 ppm Ca
63 ppm Mg
159 ppm Carbonate
631 ppm Sulfate
And I am told by the AHS staff that the Burton Salts blend really smells bad on its own, which would seem to indicate ingredients besides just gypsum and papain.
regarding these information as
1ppm=1 mg/L solution
and as:
- M(Ca)=40.08 g/mol
- M(Mg)=24.3 g/mol
- M(CO3)=60.01 g/mol
- M(SO4)=96.07 g/mol
and
- M(CaSO4)= 136.12 g/mol - 172.172 g/mol (dihydrate)
- M(MgSO4)= 120.37 g/mol - 246.47 g/mol (heptahydrate)
- M(CaCO3)= 100.9 g/mol -
we can say that 1L of Burton salt solution should contain :
0.004 mol CaSO4 = 0.690g
0.0026 mol MgSO4 = 0.640g
0.0026 mol CaCO3 = 0.262g
which mean that for a 19 L / 5gal batch you should use :
12.92 g CaSO4 calcium sulphate ( gypse)
12.17 g MgSO4 Magnesium sulfate (Epsom Salt)
4.978 g CaCO3 calcium carbonate (E504) ( laxative at high concentration)
However it is stated there are Potassium Chloride in this, but no indication of K+ or Cl- ppm are indicated. If there is really some I have no idea how much, but it will only give a salty and bitter taste. It should be a typo for Calcium Chloride (CaCl2) according to
http://www.brewersfriend.com/water-chemistry/ to obtain the desired amount of Ca, one should add 3.5g for 19 l.
Also no indication are given about presence of calcium carbonates but to obtain the proportions it should have some or some baking soda to adjust CO3!
Main ingredient of Burton water remains calcium sulphate ( gypse)
Finally papain is a protein extracted from papaya: papaya proteinase I
It is used to tenderize meat, it is excellent to destroy proteins.