A method of making calcium-2-hydroxy-4-(mercaptomethyl)butanoate includes combining
and mixing 2-hydroxy-4-(mercaptomethyl)butanoic acid and a calcium salt selected
from calcium oxide and calcium hydroxide and water in a first reaction zone. The
combining and mixing step is carried out over a first period of 3-120 seconds.
The resulting reaction mixture is transferred at the end of the first period from
the first reaction zone to a second reaction zone, the transferring step being
carried out over a second period of 3-60 seconds. Heat generated by reaction between
the 2-hydroxy-4-(mercaptomethyl)butanoic acid and the calcium salt in the second
reaction zone is allowed to drive off sufficient water to produce a product mixture
containing less than 5% (m/m) water.
