Why "Melted Cheese" Really Isn't Melted

Abstract

Contrary to what is commonly called "melting," cheese actually does not undergo a melting process. Instead, cheese undergoes what is called a "glass transition." At or below the glass transition temperature Tg, or brittle ductile temperature Tb, the cheese exhibits a hard, or "glassy" state. Above these temperatures, it turns into a "rubbery" solid that flows easily. Tests on the physical properties of American process cheese were performed to evaluate these temperatures (Tg and Tb) and this flow as a function of cheese moisture content. Samples of three different moisture contents were tested to find the brittle-ductile temperature (the temperature at which the cheese yields gradually as opposed to breaking in a brittle manner due to heating or increased moisture content) by the 3-point bend test, the extent to which the samples flow under gravity when heated to 100C by the Schreiber test, and the glass transition temperature by differential scanning calorimetry (DSC).