There is two common style of mozzarella — fresh mozzarella and low-moisture mozzarella. And one thing you have probably noticed is that fresh mozzarella is often sold in liquid. Have you ever wondered why this is the case?
The liquid could be water, whey, or salted brine. You can drink or use it, but it’s going to be bland and likely unpleasant. Sometimes, you’ll also see milk solids floating around and that’s completely normal.
The main reason is to preserve the freshness of the mozzarella, and it also helps keep the cheese from drying out. For instance, if you left a slice or ball of mozzarella in the fridge uncovered without water, it’s likely to get harden and dry up very soon. By storing it in liquid, you are helping to extend its delicate texture and flavor for slightly longer periods of time.
Also when making mozzarella cheese, an important step (known as pasta filata) is to plasticise the cheese by stretching the curd in hot water (~80 ºC) and immediately dropping it into cold water to cool it down (~65ºC). That will hold the physical stretchy characteristics of the cheese until it’s served. For best quality, fresh mozzarella is often stored and sold in the water while it is being made.
The salt concentration of the brine is around ~20% sodium chloride (salt) and <1% calcium chloride . Calcium chloride is usually added to maintain the equilibrium of calcium ions in the solution. Calcium is important for mozzarella stretchability, water holding, and meltability. Without it, the mozzarella cheese is going to swell and soften much faster.
The downside — of course — is the fresh mozzarella will have a high moisture content. It’s great for salad, but it will also make your toast or pizza soggy before it’s even melted. You can read my other article where I discussed why mozzarella cheese doesn’t melt well here and the solution.