Carbohydrate composition of prebiotic supplemented infant formula

Abstract

Oligosaccharides, one of the main components of human milk, promote the growth of probiotic bacteria such as lactobacilli and bifidobacteria, in the colon, a microflora with beneficial effects on infant health. Since cow's milk, the source of most infant formula contains oligosaccharides in a very low concentration, in recent years, to mimic the beneficial effects of human milk an increasing number of infant formulas are supplemented with prebiotic carbohydrates. Despite the importance of these compounds in the diet during the first months of infant's life, no data are available on the detailed composition of the carbohydrate fraction of supplemented prebiotic infant formula. The purpose of this study was to determine the composition of the oligosaccharide fraction present in twenty eight commercial infant formula using GC-FID and HPLC-RID. After precipitation of fat and protein by Carrez reagents, analysis of supernatant solutions was performed by HPLC-RID in isocratic mode using acetonitrile:water (55:45, v:v) as mobile phase on a Kromasil NH2 column [2]; and by GC-FID using a HT5 aluminium-clad column. To avoid interference in the GC analysis of galactooligosaccharides (GOS), samples containing maltodextrins were previously treated with β-amilase. The results showed that the simultaneous use of both analytical techniques provided a complementary information on the oligosaccharide composition. The analyses by HPLC-RID allowed the detection and quantification of oligosaccharides with a degree of polymerization up to 21; while GC-FID analyses permitted the quantification of the minor monosaccharides, disaccharides and prebiotic oligosaccharides such as GOS and fructooligosaccharides (FOS). Of the 17 samples with added prebiotics 7 have GOS in a content of 2.9 to 7.2 g/100 g dry matter (DM), 6 contained a mixture GOS/FOS (4.0 to 7.2 g/100 g DM) and 4 have FOS (0.1 to 2.5 g/100 g DM). Although the oligosaccharide composition is not disclosed in the label of products, the total prebiotics content found was similar to the values declared, with exception of samples containing only FOS as prebiotic source, probably due to presence of inulin with higher DP difficult to quantify.