Lipase-catalyzed transesterification offers potential for PUFA-enriched solid fats.

Omega-3 polyunsaturated fatty acids (PUFAs), especially long chain EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), are widely recognized to have a strong positive influence on human health. However, our intake of these fatty acids is usually minimal.

A good way to raise the PUFA content in our diets would be to enrich edible fats and oils. For this application, transesterification seems to have advantages over other lipase catalyzed reactions, since no further purification procedures would be needed if the hydrolysis process is closely controlled.

The goal of Mexican researchers was to study the transesterification reaction between a DHA-rich fish oil and a fully hydrogenated soybean oil (FHSO). This approach could be one way to develop PUFA-enriched solid fats.

All of the reactions were performed at 70 C in batch reactors placed in an orbital shaker and agitated at 300 rpm. Lipases from Thermomyces lanuginosus (TL IM), Rhizomucor miehei (Chyrazyme L9) and Pseudomonas cepacia (Amano PS) were tested at two substrate-to-weight ratios--70:30 and 80:20--for their ability to catalyze the transesterification reaction. Molecular sieves were added to the reaction mixture to prevent undesirable hydrolysis from taking place.

The transesterification process was monitored by following the changes in the triacylglycerol species present in the reaction mixture using high-performance liquid chromatography. Change in tristearin concentration was used to indicate the progress of the reaction.

The results showed that, after 12 hours of reaction, the hydrolysis was less than 10%. Consumption of tristearin ranged from 40%, for lipases L9 and PS, to 60% when the scientists used a catalyst. The presence of newly formed triacylglycerols, formed mainly by stearic acid and DHA, in the reaction mixture is a clear indication of the latter. The relatively low level of hydrolysis suggests that the use of molecular sieves is an effective way to control such undesirable process.

Further information. A. Lopez-Hernandez, Instituto Tecnologico de Veracruz, Calzada Miguel Ange de Quevedo 2779, Col. Formando Hogar, Veracruz 91897, Mexico; phone/fax: [phone]; URL: http://www.itver.edu.mx/.