The shakes (significantly not called milk shakes) are like aerated Kaopectate.
--Food critic Mimi Sheraton on McDonald's shakes
Unlike say, the ice cream soda (invented in 1874 by Robert M. Green) or the I-Scream Bar, a.k.a. Eskimo Pie (invented in 1919 by Christian Nelson), no one knows who mixed the first milk shake. But there is one person responsible for the evolution of the notorious fast-food milk shake.
According to both John F. Love's "McDonald's Behind the Arches" and Stan Luxenberg's "Roadside Empires," Ray Kroc, sort of the Henry Ford of hamburgers, was associated with almost every modern twist in milk-shake technology. Without the milk shake, McDonald's as we know it would not exist.
When he was selling paper cups for the Lily-Tulip company in the late '20s and early '30s, Kroc persuaded the owner of Chicago's Walgreen Drug Co. to sell milk shakes to go--in Kroc's paper cups. Then he discovered that one of his paper cup clients, a dairy bar owner named Ralph Sullivan, made shakes without ice cream; Sullivan had come up with the concoction called ice milk.
Kroc convinced Earl Prince, owner of a chain of Chicago ice cream stands, to try the new method--to sell more cups. Prince liked the idea of quick shakes so much that he devised a new mixer that could whip up five shake batches at the same time; Kroc was right there to help him market the thing. As president of the Malt-A-Mixer Co., he persuaded hundreds of soda fountains to convert to the new Multimixers.
Later, as the war wound down and families moved out of cities and into suburbs, many soda fountains closed. Kroc needed a new market for his Multimixers. It was then that he paid a visit to a hamburger stand in San Bernardino that was doing such phenomenal business--20,000 shakes sold a month!--it needed eight Multimixers. The "shake department" took up a fourth of the burger stand and required two full-time "shakemen" to operate. The place was, of course, McDonald's.
Once Kroc got the approval of brothers Richard and Maurice McDonald (Dick and Mac), he started the legendary chain of McDonald's franchises, all outfitted with his Multimixers. But Kroc didn't stop there; he immediately streamlined the whole shake operation. Instead of having the shakemen (no women were hired) hand-dip the frozen ice-milk base, Kroc had the franchises switch to an easy-to-store liquid milk shake mix.
But getting that classic McDonald's thickness and taste that so offend the Mimi Sheratons of the world took time. Eventually, Kroc had a special stabilizer devised that made the shakes thick with ice crystals and milk solids. (Yes, there is milk in a McDonald's shake.) Kroc felt that these McDonald's shakes would "wear better" on customers than traditional ice-cream-and-milk shakes; customers wouldn't feel bloated after drinking a McDonald's shake.
By 1970, Multimixers were replaced by all-in-one shake machines called Taylor Freezes--the final link in bringing America pre-made, instant shakes-on-tap.
Has this made milk shakes any better? As one anonymous shake fan said, "Taste isn't that important; it's the slurp that counts."