interesterification

Interesterification is a process that rearranges the fatty acids attached to the glycerol backbone in triglycerides, the main constituents of fats and oils. By redistributing fatty acids without changing the overall fatty acid composition, the technique alters the physical properties of the fat, such as melting behavior, crystallization, and texture. This makes it a common tool for formulating fats used in spreads, bakery shortenings, and confectionery fats.

There are two broad approaches: chemical and enzymatic interesterification. Chemical interesterification uses chemical catalysts, such as alkaline reagents or acids, at elevated temperatures to randomize the fatty acid distribution among triglycerides. Enzymatic interesterification uses lipases, providing milder conditions and, in some cases, regioselectivity or specificity that allows more controlled reshuffling of fatty acids and the creation of targeted triglyceride compositions. Within enzymatic methods, directional or selective interesterification can favor the formation of triglycerides with specific fatty acids in particular positions on the glycerol molecule.

Applications focus on achieving desirable melting profiles and texture without increasing trans fats. Interesterified fats are commonly used to produce trans fat–reduced margarines and shortenings, spreads with improved spreadability at refrigeration temperatures, and fats tailored for confectionery and bakery products. The technique offers flexibility and chemical modification without changing total fat content, but it can involve higher costs, process complexity, and regulatory considerations related to catalysts and enzymes.