Why Does Mozzarella Cheese Taste Bitter?

Last Updated on January 17, 2024 by Aaron

If you find your mozzarella cheese has a distinct bitter taste, It doesn’t necessarily mean that the cheese is bad or spoiled; it’s more likely a result of the making process and the type of ingredients used in its production. In the modern production of cheese, bitter taste is generally considered a defect, and this is a common mistake among new cheese makers.

First of all, rennet itself can carry bitter flavors especially when a higher concentration is used. If you’re using vegetable rennet, it will impart a slightly more bitter taste than an animal- or microbial rennet/enzyme. And It’s way noticeable when you aged the cheese.

The bitter taste is the result of bitter compounds produced, which relates to the calcium content of milk and the coagulants you used. The cheese protein — casein — goes through proteolysis (action by enzymes) and develops various bitter amino acids peptides. It’s common to have these compounds in most cheeses but at an unnoticeable level, that’s why you will sometimes taste a bit of bitterness in cheese which is ok. But the accumulation of peptides over time will eventually create a more pronounced bitterness.

If you are making mozzarella cheese at home, using acids such as vinegar or citric acid to set the cheese is a popular method. But you need to avoid using too much as it will alter the acidity by a lot and thus further increased the proteolytic reaction. It’s best to adjust it to around pH 5.5-5.7 for good stretchability, slightly lower if you’re using rennet. Read my other article where I discussed why mozzarella cheese doesn’t stretch well.

To reduce the bitterness, you can try to drain more whey or add more salt to the brine water. It is to dilute and adjust the pH while maintaining the water activity and redox potential.

Another possibility for the bitter taste is contamination with bacteria or mold. The spoilage or contamination can secrete enzymes to facilitate breaking down the cheese, which contributes to off-flavours such as bitterness. This is usually easier to spot, we can just look for the signs of mozzarella spoilage like this.


  1. Nicosia, Fabrizio Domenico et al. “Plant Milk-Clotting Enzymes for Cheesemaking.” Foods (Basel, Switzerland) vol. 11,6 871. 18 Mar. 2022, doi:10.3390/foods11060871
  2. Kirin, S. (2001). ‘Bitter taste – cheese failure’, Mljekarstvo, 51(4), str. 327-337. Preuzeto s: https://hrcak.srce.hr/1916 (Datum pristupa: 27.11.2022.)
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