Texture Basics

There are many factors that affect cheese texture. Cheese composition, acid development, and protein breakdown are some of the most important factors.

Composition

Cheese has a few main parts: protein, fat, water, and sugar (lactose). Each of these can have direct and indirect effects on the final texture and mouthfeel of cheese. As mentioned in previous posts, the main structure of cheese is casein protein. Casein micelles aggregate and form a 3-D matrix. The glue that holds these proteins together is calcium. You can think of this matrix like a sponge. When you look at a sponge, imagine all the “spongy” material is the casein, and all the holes in the sponge are gaps in the casein matrix that are filled with things like fat and serum (whey/water).

Having extra fat in this structure can soften it overall. Imagine fat getting in the way of those caseins and preventing them from packing in too tight. This is one of the reasons why many high-fat cheeses end up being soft. (think havarti or butterkäse)

High amounts of moisture can also lead to a softening effect. The mechanism behind this is a little more complex, but imagine what happens when you soak a sponge in water —- it softens and is more easily squeezed. (think fresh mozz) In addition to cheese composition we’re going to talk about two main reactions occurring in cheese as it ages: proteolysis and acid development.

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Proteolysis

Proteolysis is the breakdown of protein. Since casein protein is the main structure of cheese, proteolysis can cause cheese to soften/breakdown over time. Proteases are enzymes that cause proteolysis to occur. These can come about through various ways. A few ways include:

• Coagulation enzymes (e.g. rennet) can break down protein. Rennet, after all, is a protease. Rennet activity can also cause bitterness; as protein breaks down, bitter peptides can form.
• Proteases from the starter bacteria can break down proteins with time.
• Proteases from surface mold/bacteria can break down proteins near the surface of certain cheeses. This is partly responsible for Brie’s texture as we already discussed.
• Proteases from non-starter lactic acid bacteria (NSLAB) can break down proteins.
• Endogenous proteases found in the milk from the get-go, like Plasmin. However most of these don’t survive pasteurization, so this may be seen more in raw milk cheeses.

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Acid Development

Acid is being produced by starter cultures right from the start. They are eating up the lactose and spitting out lactic acid. Here's the thing about acid, it dissolves calcium (think about how acidic soda is bad for your teeth). Calcium is the glue that cross-links protein (casein) and gives the cheese its structure. So with calcium being dissolved, the casein network is "loosening" and the cheese is getting more brittle/softer. (think aged cheddar or really old mozz on a pizza)

There's a catch though. At lower pHs around 4.6 (i.e. when a lot of acid is produced) the casein micelles themselves begin to agglomerate very strongly. This is called the isoelectric point of casein and this yields a very firm cheese that won't melt (think about feta and cottage cheese curds).

Overall, high pH results in a tough protein structure due to lots of calcium glue. This kind of cheese won’t melt well. As the pH goes down (acid goes up), the structure softens due to the calcium glue dissolving away and a cheese will begin to melt better. If the pH gets low enough the casein proteins begin to become attracted to each other and the structure toughens again resulting in cheese that won’t melt. As you see, a cheesemaker must tread this line carefully in order to ensure the final texture/melt profile of their cheese is what they want.

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For More Information

• Dairy Pipeline - The Melt and Stretch of Cheese
• Texture Development During Cheese Ripening