The Reason Some Ice Cream Doesn't Melt Is Easily Explained By Science

Ice cream melts when it warms up. After all, it's in the name: ice cream. But recent social media posts have thrown this conventional understanding of ice cream's properties into question. One Facebook post went viral when an Australian woman shared an image of her ice cream sandwich retaining its form after days in the sun, while a woman in Cincinnati reported the same curious outcome. Then, there's a YouTube video from a Sioux Falls radio show that's garnered nearly 7 million views. The radio jockeys put the unmelting-ice-cream phenomenon to the test, and declared that Walmart-brand ice cream sandwiches are "not real ice cream."

As unnatural as the phenomenon may seem, unmelting ice cream can be explained by a glance at the list of ingredients. Ice cream sandwiches, such as those from Walmart's Great Value brand, contain stabilizing ingredients to help the sandwich retain its shape and texture. These ingredients include monoglycerides, diglycerides, cellulose gum, guar gum, and calcium sulfate. Sugars are also substances that affect the rate at which ice melts, and ice cream has plenty of them. Taken together, all these ingredients bind some ice creams together so that even when the water content melts, the shape of the ice cream is retained.

Such ingredients may sound unusual, but they're actually quite common in processed foods. Mono and diglycerides are emulsifiers, and they're used to prevent the oils — or the fats — from separating from the water content of food. The "gums," including guar gum and cellulose gum, serve as thickeners. Calcium sulfate, too, helps maintain firmness and texture. In fact, calcium sulfate is also known as gypsum, and it's even used as plaster in construction. Common though they may be, whether such ingredients are healthy for you is a different debate.

All the listed ingredients that serve to thicken, emulsify, and stabilize ice cream are approved for consumption by the United States FDA. Let's start with the most basic ingredient: calcium sulfate, or gypsum. Gypsum's use in food has skyrocketed in recent decades as demands for vegan food alternatives, like dairy-free cheese and tofu, have become more popular. It's even taken as a supplement; easily bioabsorbable, its calcium ions can help strengthen bones. Furthermore, it's non-toxic when consumed at normal levels and highly tolerated.

Glycerides are also used in a wide range of food and non-food applications, including acting as one of the components of pen ink. They're essentially fatty acids that occur naturally in many edible plants. Around 70% of food emulsifiers in the United States are either mono or diglycerides, and they can be found in everything from breads, mayonnaise, candy, and butters. At low levels, they're basically harmless. However, glycerides do contain trans fats, a type of lipid that's dangerous when consumed in high levels.

The "food gums" are perhaps the most controversial ingredients. Some food gums, such as guar gum, contain natural fibers that are beneficial to the gut, while others can be problematic for those with digestive diseases. The Walmart-brand ice cream sandwiches that sparked the entire debate contain carob bean gum, cellulose gum, and carrageenan. Studies on both humans and other animals have suggested that the latter two ingredients, cellulose gum and carrageenan, may be linked to inflammatory bowel disease. Furthermore, critics have pointed out that the use of such ingredients is rarely necessary, as their emulsifying effects are really just for aesthetics. As with all things, moderation is key, though cutting out ultra-processed foods from your diet is ultimately the healthiest option.