2025-10-08: Like some other posts that I am retaining but updating to the new style, just wanted to pop a note in here that this was years ago [16 in this case] and I have no idea to what degree any of this is factual, anymore. It is left as a product of its time with only minor fixes.
I did strike a line about preferring milk and eggs over plastic gooop. Being a person who can no longer eat milk and eggs, it felt a bit dishonest to leave it in. Just pretend it is still there if that sort of thing bothers you.
In comment on a blog entry Alicia made about the future of food and such, I commented that soft serve ice cream contains plastic.
Today she mentioned not trusting fast food style ice cream because of that comment. I realized that before I traumatized the poor woman off of her dietary splurges, I needed to track down and clarify the facts. And here they are.
If, by plastic, you mean "from a petroleum base", then no. There is no plastic in a McDonald's shake. If you mean plastic as in "non natural combinations of C+H+O in chains designed for for physical texture and capabilites" then yes, there is. I finally tracked down the Snopes article on it after a god-awful number of failed searches involving results such as "plastic cup used for milkhshake!" over and over again. The origin of the "myth" seems to be the 90s, which is where I first heard it. While it posits the myth is false, it does include a list of ingredients. In it, there are three plant derived materials that are a likely origin of the myth: carrageeanan, guar gum, and Carboxymethyl cellulose. It would not surpise me if someone heard of these, went "there are chemicals in my milkshake!" and by two or three retellings, these weird-sounding, plastic-like substances had morphed into panic over styrofoam.
All three are derived in various ways from plant products. All three are widely used (the list of uses ranges from personal lubricants to cosmetics to food to drilling operations). You can read more about them on their various Wikipedia pages, but all three are used to increase the "creaminess" of soft serve icecream by preventing water crystal formation, forming something of a lattice the helps trap air, and various emulsifier properties. Basically, fast food ice cream is actually milk with these gums mixed in instead of cream and eggs. Hence the reason you see names like "Soft-Serve" and "Ice Dream" with a trademark after it.
Guar gum helps to prevent the water crystals, the celluous gum (CMC) thickens witout gelling, and the carrageenins thin with pressurized and re-thicken afterwords, making them ideal for the soft-serve ice cream market. There are some intestinal issues involved. Carrageenins might eat away at your intestinal track, guar gum might "pour" through you, but cellulose gum is largely neutral, doing more or less nothing on it's way through your body. These presumably do not have the "let's all get stuck in the kidneys" power of other plastics, but there you go. That is the truth of "plastic in the milkshakes". Hope that clarifies a little.