Volume 90, Issue 1, July (2003), pp. 127-133 © The Author 2003
doi:10.1079/BJN2003882

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Quantification of non-protein nitrogen components of infant formulae and follow-up milks: comparison with cows' and human milk

I.M.P.L.V.O. Ferreira^1
1CEQUP/Serviço de Bromatologia, Faculdade de Farmácia da Universidade do Porto, R. Aníbal Cunha 164, 4050-047 , Porto, Portugal

 (Received 5 August 2002–Revised 24 January 2003–Accepted 21 February 2003)

The composition of fourteen infant formulae and six follow-up milks with regard to their free amino acids (including taurine), free nucleotides, orotic acid, and free and total l-carnitine content was studied. The levels found were compared with the limits established in European legislation and with the composition of human and cows' milk samples. HPLC methodologies, optimized and validated for the matrices under study, were used, except for free and total l-carnitine contents that were quantified using a flow-injection manifold, also optimized and validated for the matrices under study. Global statistical treatment of the results by cluster analysis indicated similarities between the contents of the N compounds under study of infant formulae, follow-up milks and cows' milk and differences with regard to human milk composition. The principal component analysis showed that 60·2 % of the variation in data was due to the first principal component, and the second component represented 23·8 % of the total information. Nucleotide profiles, orotic acid, and free and total l-carnitine contents explain the main differences observed between human milk and the other milks studied (cows' milk, infant formulae and follow-up milks). Cows' milk is distinguished from infant formulae and follow-up milks mainly owing to the different uric acid contents and free amino acids profiles.

Keywords:
Free amino acids, Nucleotides, Orotic acid, Uric acid, l-Carnitine, Infant formulae

Abbreviations:
AMP, adenosine 5′-monophosphate, C, cows' milk, CMP, cytidine 5′-monophosphate, FM, follow-up milks, GMP, guanosine 5′-monophosphate, H, human milk, IF, infant formulae, IMP, inosine 5′-monophosphate, PCA, principal component analysis, UMP, uridine 5′-monophosphate