Protein milk consists of a quart of buttermilk, or of a pint of buttermilk and a pint of water, in which is mixed the drained curd from a quart of whole milk. The curd is usually prepared by adding one half ounce of liquid rennet to 1 quart of whole milk, heating to 100 F., allowing the mixture to stand until clotted (usually fifteen minutes) and pouring the semisolid coagulum into a cheesecloth bag which is then suspended until the whey drains away (about two hours). The drained curd is usually then finely divided by forcing it with a wooden potato masher or a large spoon through cheesecloth spread over a sieve. The same proportions are used in preparing larger amounts.
During the summer months, when several gallons of protein milk are used daily in children's hospitals, this process requires several hours of arduous labor. Several mechanical devices have been
DAVISON WC. AN APPARATUS FOR THE RAPID PREPARATION OF PROTEIN MILK. Am J Dis Child. 1925;30(2):238-239. doi:10.1001/archpedi.1925.01920140098010