Determination of the positional distribution of fatty acids in butterfat triacylglycerols

Revisión: Aplicación de las técnicas cromatográficas al estudio de triglicéridos y esteroles de la grasa de leche / Review: Application of chromatographic techniques to the study of triglycerides and sterols of milk fat

The latest developments in analytical techniques, mainly chromatographic, for the study of triglycer ides (TG) and sterols in milk fat are revised. Gas chromatography (GC) with packed or short capillary columns has been used to separate TG according to their carbon numbers (CN) and can be applied to the detection of foreign fats in milk fat. Combined or hyphenated chromatographic techniques are indispensable in order to identify and quantify individual molecular species of TG: thin layer chro matography (TLC) or high performance liquid chromatography (HPLC) with Ag+ as prefraction stage, followed by supercritical fluid chromatography, GC with long capillary column, and HPLC with reverse phase and mass spectrometry as detector. These techniques, along with non-specific and/or specific hydrolysis procedures, have allowed a better knowledge of the positional distribution of the fatty acids within the molecules of TG. Concerning the study of the esterol fraction, the supression of the stages of fat extraction—separation of the insaponifiable and derivatization—previous to the analy sis by GC represents a considerable advance that should be in part attributed to the improvement of the chromatographic techniques.

Regiospecific analysis of fractions of bovine milk fat triacylglycerols with the same partition number

Bovine milk fat was fractionated using preparative reversed-phase high-performance liquid chromatography. The conditions consisted of two successive linear gradients of acetonitrile and tert-butylmethylether, followed by a final isocratic mixture of the two eluants, leading to triacylglycerols grouped by their partition number (PN). Fractions corresponding to partition numbers 32 to 50 were isolated and analyzed for fatty acid distribution between sn-1,3 and sn-2 positions by Grignard degradation. Results showed that the fatty acid distribution in milk fat triacylglycerols is nonrandom. The distribution of short-chain fatty acids, stearic (predominantly at sn-1,3 position) and palmitic (predominantly sn-2 position), did not change with triacylglycerol size. Medium-chain fatty acids were predominantly located at sn-2 position, but their proportion at this position decreased with triacylglycerol size. Oleic acid distribution was also size-dependent in that it was located in high proportions at sn-2 position in smaller triacylglycerols and vice versa. Results also showed that the sn-2 position was more unsaturated than sn-1,3 position in the PN range from 32 to 40, but it was more saturated in triacylglycerols with higher PN.

Lipase catalyzed modification of milkfat

Decreasing consumption of high fat milk and dairy products is driving the dairy industry to seek other uses for increasing surplus of milkfat. Enzyme catalyzed modification of milkfat using lipases is receiving particular attention. This review examines lipase-mediated modification of milkfat. Especial attention is given to industrial applications of lipases for producing structured and modified milkfat for improved physical properties and digestibility, reduced caloric value, and flavor enhancement. Features associated with reactions such as hydrolysis, transesterification, alcoholysis and acidolysis are presented with emphasis on industrial feasibility, marketability and environmental concerns. Future prospects for enzyme catalyzed modification of milk fat are discussed.

Use of continuous culture to screen for lipase-producing microorganisms and interesterification of butter fat by lipase isolates

The continuous cultivation technique was used to investigate the screening for lipase-producing microorganisms from four commercial starters suitable for the degradation of domestic wastes. Using this technique, three strains of lipase-producing bacteria were isolated and identified: Pantoea agglomerans (BB96CC1, BB168CC2) and Pseudomonas fluorescens (BW96CC1). In addition, butter fat induced more lipase production when present in the growth medium. Interesterification of butter fat triacylglycerols by enzymatic extracts of the isolated strains of microorganisms resulted in an appreciable interesterification yield, implying that hydrolysis was suppressed and interesterification of butter fat triacylglycerols was maximized in a microemulsion free-cosurfactant system.

Methods for the analysis of triacylglycerols

This article discusses the methods most commonly employed in the analysis of the triacylglycerols (TAGs) in natural fats and considers the main advantages and disadvantages of each and the techniques for optimising analytical conditions. Complete analysis of the composition of a natural fat calls for a method of extracting and purifying the triglyceride fraction, normally by preparatory thin-layer and column chromatography. Determination of the individual components of triglyceride mixtures still entails certain difficulties, namely, the separation and identification of the TAGs in natural fats. High-performance liquid chromatography (HPLC) offers significant advantages over gas and thin-layer chromatography. Many workers have developed non-aqueous, reversed-phase HPLC systems capable of successfully resolving complex mixtures of TAGs, and combining reversed-phase (RP) HPLC and argentation chromatography may improve the results. Identification of the TAGs separated by HPLC becomes an extremely complex task if many different fatty acids are involved and if the sn-stereoscopic positions on the glycerol are to be determined. Enzymatic analysis and chiral-phase chromatography are capable of localising fatty acids on the TAG molecule. In closing, some of the most interesting biomedical applications of TAG analysis are summarised.