Science Byte

Why does Provolone smell like baby vomit?

Butyric is also known as “rancid”, “piquant”, or “baby’s breath”. Its causative compound, butyric acid, can be found in many different cheeses at low amounts and is an important part of total flavor profile. When in higher concentrations, its own flavor begins to dominate and becomes much more prominent.

butyric acid

Structure of butyric acid

Butyric acid comes about through the breakdown of fat. Enzymes called lipases clip off fatty acids from the fat molecule as we’ve already discussed here. Some of these fatty acids will be butyric acid. The lipase enzymes can be found naturally in raw milk or are sometimes added by the cheese maker. Excessive handling of the milk could also lead to rancid defects due to damaging the fat globules and exposing them to the endogenous lipases. Butyric acid is a four carbon acid. Its small size makes it quite volatile. It can usually be strongly perceived in headspace of packages or after swallowing.


While we often talk about flavors and aromas being caused by certain compounds, it’s important to remember that the unique taste and aroma of cheese is caused by a whole menagerie of chemicals. Cheese flavor is definitely a case of the whole being greater than the sum of its parts.