Free amino acid content in infant formulas

Infant formula is the sole nutrition and food source for many infants. Information on the free amino acid (FAA) content of formulas, particularly those that are protein hydrolysate based, is limited, despite emerging evidence for the role of FAAs in regulating eating behaviour. The purpose of this paper is to measure levels of essential, semi-essential, and nonessential FAAs in commercially available infant formulas to provide a foundation for future research examining the influence of FAAs on infant development.

Using an automatic amino acid analyzer, we measured the concentrations of FAAs in four types of formula: two cow milk (CMF); three soy protein (SPF); and three protein hydrolysate (PHF), one of which was a partial hydrolysate (pPHF) and two of which were extensive hydrolysate (ePHF).

It was found that the amount and number of FAAs varied significantly across formula types: for CMF, total FAAs ranged from 523-864 μmol/L, with taurine being the most prominent; SPF, 1933-2450, methionine; pPHF, 2329, taurine; and ePHF, 80375-85445, leucine. ePHF had the highest levels and the most diversified profiles of FAAs.

Striking discrepancies exist for FAA profiles of infant formulas. Comparison of these data to published psychophysical data on the taste qualities of individual FAAs provides insights into the unique flavor profiles of infant formulas. Overall, the data from this study provide a necessary foundation for future research examining the influence of FAAs in formulas on infant growth and development.

Published data on the FAA content of PHF is limited, despite their increased availability and use. This research is the first to report the FAA content of partial and extensive PHF, and to compare these values to CMF and SPF.