Fat interesterification

In the food industry and biochemistry, interesterification (IE) is a process that rearranges the fatty acids of a fat product, typically a mixture of triglyceride. The process implies breaking and reforming the ester bonds C–O–C that connect the fatty acid chains to the glycerol hubs of the fat molecules. These reactions are performed by inorganic catalysts, yielding what is called chemical interesterification (CIE) in the industry; or by enzymes, in the so-called enzymatic interesterification (EIE). This process is typically used to adjust the physical characteristics of the fat, such as melting point and plasticity, for specific uses. It can be used, for instance, to turn oils into solid or semisolid products by combining them with other solid fats. It can also be used to prevent separation of solid fractions in palm oil and lauric fats, slow rancidification, or create oils more suitable for deep frying. In contrast to hydrogenation, interesterification is generally the original distribution of fatty acids in the product and hence is expected to preserve its nutritional and health attributes. However, those other techniques may still be applied to the starting fats or to the products of IE, and the latter may be blended with other fats. Also, some of the new triglycerides produced by IE may be fractionated (separated) through controlled crystallization. Interesterified fats are used in many industrial food products, including cookies, crackers, biscuits, cakes and icings, dairy fat replacers, pie crust, popcorn, flatbread and tortillas. Typically the feedstock (starting product) is a mixture of two or more oils. In particular, unsaturated vegetable oil can be interesterified with a fully hydrogenated version thereof, as in the illustration to the right. This procedure yields less saturated fat without creating the trans fat that would be produced by partial hydrogenation. The reaction does not go to completion, and the product will be a mixture of triglycerides with different amounts of saturation.