Protein quality in commercial milk-based infant formulas

Protein quality was evaluated in thirteen powdered and liquid milk-based infant formulas. The parameters evaluated and found most suitable to describe protein quality in such products were: total hydroxymethylfurfural, protein-reducing substances, lysinoalanine, available lysine, tyrosine, chemical score, in-vitro protein digestibility, calculated protein-efficiency ratio and the whey-protein/casein ratio. Lysinoalanine content was found to be one of the indices most sensitive to heat damage undergone by the product, and is correlated both linearly (p = 0.05) and directly with total hydroxymethylfurfural and protein reducing substances. The graphic representation of Quantitative Descriptive Analysis (QDA) was used to compare the various formulas. Global evaluation of the ten protein quality parameters taken into consideration revealed a modest difference between powdered and liquid formulas, which achieve mean QDA scores of 4.94 and 5.16, respectively. Powdered formulas, however, present more constant quality than liquid ones.