Types of rancidity include hydrolytic, oxidative and microbial rancidity. Rancidity typically refers to the release of aldehydes and ketones in fats that have unpleasant taste and odors.
Hydrolytic rancidity occurs when triglycerides go through the process of hydrolysis, breaking them down into their fatty acids and glycerol. These individual fatty acids are more easily distinguishable by taste and typically have an unpleasant taste and odor.
Oxidative rancidity is caused by oxidation in unsaturated oils or fats. When these types of oils or fats are exposed to oxidation, they begin decomposing into short-chain fatty acids, such as butyric acid, which gives the fats a rancid taste.
Microbial rancidity is caused by bacteria breaking down fats with enzymes, causing the fat to decompose.