Industrial engineer and recipe developer Swetha Sivakumar insists she has a surefire way to make a smooth, creamy queso from just about any melting cheese. The innocuous ingredient is aspirin-free Alka-Seltzer. (It's crucial that you use the aspirin-free variety!) The sodium bicarbonate and citric acid that are used to relieve heartburn create salt when the tablets are added to water. The concept is not new to the food science community, Sivakumar explains. James Kraft himself used sodium citrate to make processed cheese.
She stumbled upon the hack when researching Eno, an Indian Alka-Seltzer equivalent developed by a British pharmacist more than 100 years ago. Indian cooks have used the antacid since the 1980s to leaven breads.
Milk is this creamy emulsion and liquid, says Sivakumur. "You don't even think of solid particles suspended in it but, actually, there are proteins suspended in the milk in a very delicate balance" When this balance is disrupted by adding acid rennet, the casein in particular, precipitates out. Now, you're forcing the casein to precipitate out by adding the acid. Chemically, adding water back into the cheese is difficult to do. When sodium citrate is added, it absorbs water and traps the fat molecules that are in the cheese, creating a homogeneous sauce that you wouldn't have achieved if you had just heated cheese and water alone.
Sivakumar elaborates on the science behind her discovery for Serious Eats.