Hydrogenation, Fractionation and Interesterification

 Margarine Manufacture

A Brief on Margarine Manufacture

What is margarine: Margarine manufacture came to light in the 19th century as an alternative to butter. It was a popular substitute for people who could not afford butter or to whom butter wasn’t available. It can be made from either animal fat or plant oils. Most manufacturers prefer making margarine from plant oils because of their low values of saturated fatty acids especially Lauric, Myristic and Palmitic acid. Margarine plastic fats are normally produced by hydrogenation, fractionation, or interesterification.

Hydrogenation: During hydrogenation, unsaturated fatty acids are converted into saturated fatty acids in the presence of a suitable catalyst. After removal of impurities that may poison the catalyst, the oil (usually soybean or palm oil) are exposed to hydrogen gas at high pressures (2-10 atmospheres) and high temperatures (160-220⁰c). Finely divided nickel (divided to increase the surface area), at 0.01 – 0.2% serves as a catalyst. This process of hydrogenation occurs  due to isomerization of cis to trans configuration of fatty acid with the proportion of trans-fatty acids ranging between 5 – 40% in the final product.

Fractionation: This employs the mechanism of separation where the lipid is separated into solid and liquid fractions. It is usually employed in margarine manufacture from palm oil where the oil is separated into an olein and stearin fractions both of which have applications in certain margarine blends. Fractionation is limited by the sources of oils and varieties of products. 

Interesterification: Normally includes chemical interesterification and lipase-catalyzed interesterification.  In chemical interesterification, fully hydrogenated fats are blended with liquid oils as the feed-stocks usually using a lipid soluble catalyst (commonly sodium methoxide (0.1%)) at temperatures between 80⁰c to 120⁰c. Chemical interesterification randomizes the location of the different fatty acids, thereby improving the utility of the fat. Spreadability, melting point, and solid-fat content temperature profile are modified by the randomization. The chemical catalyst produces a darkening of the oil and some by-products, both of which need to be removed.

On the other hand, enzyme interesterification is a process in which a 1,3 specific lipase enzyme (from either bacterial, yeast and fungal sources) is used to catalyze the exchange of fatty acids attached to glycerol backbone of the fat in position 1 and 3 while leaving fatty acids in position 2 intact. It can achieve tailor-made fats which might have desired physical or nutritional properties unattainable by physical mixture or chemical randomization. Lipase-catalyzed interesterification conditions are mild and the process is more natural and green and would be better accepted by consumers. Enzymatic interesterification requires less severe reaction conditions; products are more easily purified, and it produces less waste than chemical interesterification. However it’s more expensive although prices for lipases are also gradually coming down, and lipase stability has been improved hence making the technology economically attractive.

References

O’Brien. R., 2009. Fats and Oils: Formulating and processing for applications. Richard D., 3^rd edition. ISBN 13: 978-1-4200-6166-6

Zhang. H, Xu. X, Mu. H, Nilsson. J, Adler-Nissen. J, Hoy. C., 2000. Lipozyme  IM-catalyzed Interesterification for the production of margarine fats in a 1 kg scale stirred tank reactor. Eur. J. Lipid Sci. Technol. 2000, 102, 411-418.

The American Oil Chemical Society Lipid Library, 2011. Edible oil processing-Modification. Enzymatic interesterification. Accessed online on January 22, 2013 from;  http://lipidlibrary.aocs.org/processing/enzinter/index.htm

 

Coultate TP. Food: The Chemistry of its components.  Fifth edition, Cabridge U.K; Royal Society of Chemistry; 2009.