Gangliosides are considered bioactive components in human infant nutrition, and their fatty acid composition alters their biological effects. We used matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) MS and GLC to analyze the fatty acid composition of the predominant gangliosides, the monosialoganglioside GM(3) [sialic acid (Sia) alpha2-3 galactose (Gal) beta1-4 glucose (Glc) beta1-1 ceramide] and the disialoganglioside GD(3) (Sia alpha2-8 Sia alpha2-3 Gal beta1-4 Glc beta1-1 ceramide), in pooled human and bovine milk, the latter being a source for gangliosides in infant formula. Compared with whole milk lipids, both human and bovine milk gangliosides were selectively enriched with certain fatty acids, and the fatty acid composition of milk gangliosides in the 2 species was significantly different. The amount of long-chain fatty acids (> or =20 C atoms) was higher in bovine milk gangliosides (GM(3): 73.71 +/- 3.39%; GD(3): 79.19 +/- 2.79%) than in human milk gangliosides (GM(3): 51.25 +/- 0.65%; GD(3): 34.04 +/- 1.80%). Tricosanoic acid (23:0) dominated in bovine milk gangliosides (GM(3): 24.05 +/- 1.37%; GD(3): 26.66 +/- 1.24%), whereas it only played a minor role in human milk gangliosides (GM(3): 2.88 +/- 0.10%; GD(3): 1.84 +/- 0.29%). We hypothesized that the differences in the fatty acid composition of milk gangliosides result in physiological distinctions between breast-fed and formula-fed infants and therefore are of importance for human infant nutrition.

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Long‐chain polyunsaturated fatty acids with 20 and 22 carbon atoms (LCPs) seem to play an important role during the rapid development of the infant brain in the late fetal and early postnatal period. These LCPs are integral constituents of biological membranes and they are involved in the regulation of functional properties like fluidity, permeability and activity of membrane‐bound enzymes. Human milk contains LCPs in an amount of 0.5–3 wt% of total fatty acids, whereas commercially available infant formulae are almost free of them. Recently, several clinical trials, primarily with preterm infants, have reported that the content of LCPs in the blood and a functional parameter like visual acuity correlate with the content of LCPs in the diet. In this clinical trial we studied the effect of different diets on the fatty acid pattern of plasma and erythrocyte lipids of healthy term infants during the first 3 months of life. Breast‐fed infants were compared with formula‐fed babies who received a commercially available formula without LCPs or a new experimental formula enriched with LCPs that was similar to human milk. The results indicate that the introduction of milk feeding leads to marked differences in the blood lipid composition during the first months of life, independent of the feeding regimen. Secondly, the supplementation of a formula with LCPs seems to result in a blood lipid composition similar to infants fed with human milk. This supports the hypothesis that the newborn term infant has a limited desaturating capacity and depends on an exogenous supply of LCPs during the first months of life.

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Many different analytical procedures for fatty acid analysis of infant formulae and human milk are described. The objective was to study possible pitfalls in the use of different acid-catalyzed procedures compared to a base-catalyzed procedure based on sodium-methoxide in methanol. The influence of the different methods on the relative fatty acid composition (wt% of total fatty acids) and the total fatty acid recovery rate (expressed as % of total lipids) was studied in two experimental LCP-containing formulae and a human milk sample. MeOH/HCl-procedures were found to result in an incomplete transesterification of triglycerides, if an additional nonpolar solvent like toluene or hexane is not added and a water-free preparation is not guaranteed. In infant formulae the low transesterification of triglycerides (up to only 37%) could result in an 100%-overestimation of the relative amount of LCP, if these fatty acids primarily derive from phospholipids. This is the case in infant formulae containing egg lipids as raw materials. In formula containing fish oils and in human milk the efficacy of esterification results in incorrect absolute amounts of fatty acids, but has no remarkable effect on the relative fatty acid distribution. This is due to the fact that in these samples LCP are primarily bound to triglycerides. Furthermore, in formulae based on butterfat the derivatization procedure should be designed in such a way that losses of short-chain fatty acids due to evaporation steps can be avoided. The procedure based on sodium methoxide was found to result in a satisfactory (about 90%) conversion of formula lipids and a reliable content of all individual fatty acids. Due to a possibly high amount of free fatty acids in human milk, which are not methylated by sodium-methoxide, caution is expressed about the use of this reagent for fatty acid analysis of mothers milk. It is concluded that accurate fatty acid analysis of infant formulae and human milk requires a careful and quantitative derivatization of both polar and nonpolar lipid classes. Sodium methoxide seems to be a reliable and time-saving method for routine fatty acid analysis of infant formulae, which should be validated by interlaboratory comparison. Anhydrous procedures based on methanolic hydrogen chloride including an additional nonpolar solvent are also suitable for infant formulae but seem to be preferable for human milk samples.