Among all the dairy ingredients, cheese is atypical in the way that its functionality is most versatile, i.e., it can be modified depending on consumer needs. There are plenty of cheese choices available for consumers in the market in a variety of forms and types. However, Cheddar and Mozzarella are by far the most popular due to their versatile flavor and functionality.

Cheddar cheese structure consists of renneted casein curd matrix embedding fat and aqueous phase. Structure of fresh Cheddar cheese is formed from matting of curd particles upon pressing giving desired firm and elastic body. This structure transforms into pasty, soft and mellow texture upon aging due to continuous breakdown of proteins and fat. Molten Cheddar cheese offers smooth, gooey and viscous texture with varying flavors depending upon the age of the cheese.

On the other hand, Mozzarella, a pasta filata variety, has a typical fibrous structure and a plastic appearance. This typical structure is created by kneading and stretching steps (also known as working) traditionally performed by hand stretching in hot water. This process causes protein molecules to coalesce with each other to form a macroscopic fibrous network consisting of protein strands oriented in the stretching direction. Fat and serum channels are also formed within the cheese matrix during this step and are important to attain optimum melt and flow functionality in pizza applications.

Compositionally, cheese is a perfect combination of fat, protein, moisture and micro components that provide desired functionality, such as melting, stretching, free oil, browning, etc. Having optimum oil release, melt and flow properties are critical for overall performance of any cheese.

Meltability of cheese is probably the most researched among all the properties of cheese. There is a wide span of desired meltability, ranging from restricted melt to fully melted cheese, depending on its end application, such as burgers, pizza, pasta, sandwiches, soups, sauces, dips, crackers, entrees, and the list goes on. In general, cheese melting is a very complex phenomenon.

During initial heating (around 100^oF) fat starts melting and coming out on the surface of the cheese, making an impervious, hydrophobic layer, creating an environment for formation of steam bubbles. Further heating (beyond 120^oF) facilitates protein phase to soften and start flowing. Calcium, pH, moisture, aging and proteolysis play a crucial role in melting the cheese. The manufacturers of process cheese use single or combination of different emulsifiers to achieve desired meltability in cheese depending on the end application.

Fat release/free fat/oiling off is important from the visual and aesthetic viewpoint. Fat leakage occurs when the protein matrix softens and eventually collapses during heating of the cheese, allowing the fat globules to coalesce and to flow to the surface. The extent of fat release depends on the state of fat, (i.e., emulsified or non-emulsified), size and shape of the fat globules, age (extent of proteolysis) of the cheese and other conditions.

Stretching is a critical function of mozzarella cheese for pizza application. The molten casein network with a right balance of flexible and rigid forces in such a way that molten structures can pass on each other without breaking during stretching and folding action. Excessive calcium associated with cheese curd makes it harder to melt, due to formation of rigid bonds between protein strands causing early breakdown of the structure and poor stretching characters.

Browning and blistering are important properties, especially for Mozzarella types of cheeses for use on pizza. These properties are highly governed by composition, specifically lactose, moisture and fat content, extent of proteolysis, type of starter and non-starter microorganisms (lactose or galactose utilizing cultures). Oiling off can also significantly impact the browning of cheese by moderating surface dehydration.

During pizza baking the entrapped air/steam pockets result in nonhomogeneous hot spots on the surface of the dough. Number, size and color (extent of browning) of blister vary depending on the above-mentioned factors. However, impact of cheese chemistry and structure on browning and blistering properties is still not fully understood. For example, how different calcium levels would impact these properties.

Tailoring cheese molten cheese functional properties to optimum level by manipulating composition, starter bacteria and processing conditions is future area of research. Also, use of machine learning approaches to predict and control cheese functionality can bring significant commercial value to the cheese industry.

Acknowledgement: Prateek Sharma, Ph.D., acknowledges financial support from Dairy Management Inc. and BUILD Dairy, Western Dairy Center on his cheese research work.

References

• Parhi, A., Verma, A., Nair, P. and Sharma, P. (2025). INVITED REVIEW: Manufacture and quality control of Mozzarella cheese: scientific and technological advances. Journal of Dairy Science. https://doi.org/10.3168/jds.2024-26225
• The Science of Melting Cheese by Meghan Bartels, edited by Tanya Lewis, October 2, 2024, published in Scientific American. https://www.scientificamerican.com/article/why-cheeses-such-as-mozzarella-and-cheddar-melt-differently-than-ricotta/
• Sharma, P. (2022). ADSA Foundation Scholar Award: Materials science approach to the study of mechanical and diffusion properties in cheese. Journal of Dairy Science, 105 (6), 4711-4721. https://doi.org/10.3168/jds.2021-21093