Which of the following best describes reversion in oils?

Reversion in oils primarily refers to the development of off flavors, particularly as a result of the oxidation of fatty acids. This process can occur in oils when they are stored for extended periods or exposed to light and heat, leading to the breakdown of certain components within the oil. The oxidized compounds can create undesirable flavors and aromas, which can be perceived as rancid or stale.

In this context, the other options do not accurately describe reversion. Formation of glycerol is a particular chemical process but is not directly associated with reversion. Emissions of smoke are related to the heating of oils past their smoke point and are indicative of thermal degradation rather than reversion. The breakdown of fatty acids can occur through several mechanisms, including reversion, but it does not specifically encapsulate the flavor development aspect that defines reversion. Thus, the most accurate description of reversion in oils is the development of off flavors.