Catalytic Production of Conjugated Fatty Acids and Oils

Abstract

The reactive double bonds in conjugated vegetable oils are of high interest in industry. Traditionally, conjugated vegetable oils are added to paints, varnishes, and inks to improve their drying properties, while recently there is an increased interest in their use in the production of bioplastics. Besides the industrial applications, also food manufactures are interested in conjugated vegetable oils due to their various positive health effects. While the isomer type is less important for their industrial purposes, the beneficial health effects are mainly associated with the c9,t11, t10,c12 and t9,t11 CLA isomers. The production of CLA-enriched oils as additives in functional foods thus requires a high CLA isomer selectivity. Currently, CLAs are produced by conjugation of oils high in linoleic acid, for example soybean and safflower oil, using homogeneous bases. Although high CLA productivities and very high isomer selectivities are obtained, this process faces many ecological drawbacks. Moreover, CLA-enriched oils can not be produced directly with the homogeneous bases. Literature reports describe many catalytic processes to conjugate linoleic acid, linoleic acid methyl ester, and vegetable oils rich in linoleic acid: biocatalysts, for example enzymes and cells; metal catalysts, for example homogeneous metal complexes and heterogeneous catalysts; and photocatalysts. This Review discusses state-of-the-art catalytic processes in comparison with some new catalytic production routes. For each category of catalytic process, the CLA productivities and the CLA isomer selectivity are compared. Heterogeneous catalysis seems the most attractive approach for CLA production due to its easy recovery process, provided that the competing hydrogenation reaction is limited and the CLA production rate competes with the current homogeneous base catalysis. The most important criteria to obtain high CLA productivity and isomer selectivity are (1) absence of a hydrogen donor, (2) absence of catalyst acidity, (3) high metal dispersion, and (4) highly accessible pore architecture.

Synthetic methods to obtain conjugated linoleic acids (CLAs) by catalysis – A review

“…Beside their utilization for production of pure CLA at large scale, microorganisms also play an important role in increasing the CLA-content of foods. The CLA content of fermented dairy products or cheeses could be raised by using microbial strains with high CLA-producing potential (PHILIPPAERTS et al, 2011). The enhancement of CLA content in food with strains that are capable of the formation of CLA from linoleic acid was achieved recently by ANDRADE and co-workers (2012).…”

“…In metal catalysed synthesis of CLA both homogeneous and heterogeneous catalytic methods are developed, but these methods have not been implemented in practice yet (PHILIPPAERTS et al, 2011).…”

“…1) was discovered two decades ago (HA et al, 1989) and this isomer is predominant in the natural products used as foods. The main foods rich in CLA are milk, dairy products, meat and fat of the ruminants, as this isomer is produced by the bacteria of the rumen microfl ora.Nowadays, CLAs are obtained for industrial purpose from vegetable oils that are processed at high temperature (PHILIPPAERTS et al, 2011). The basic method in the industrial approach is the isomerisation of linoleic acid (LA) with basic catalysis by which the amounts of the two formed isomers (c-9,t-11 and t-10,c-12 CLA) are almost equal, and the yield is quite high.…”

“…Nowadays, CLAs are obtained for industrial purpose from vegetable oils that are processed at high temperature (PHILIPPAERTS et al, 2011). The basic method in the industrial approach is the isomerisation of linoleic acid (LA) with basic catalysis by which the amounts of the two formed isomers are almost equal, and the yield is quite high.…”

“…The synthetic methods for obtaining CLA, in general, can be categorized in three groups: microbiologic, catalytic (both homogeneous and heterogeneous), and photocatalytic methods (PHILIPPAERTS et al, 2011). In this review article we wish to present the different synthetic methods developed for the obtaining of CLAs.…”