The composition and content of amino acids in infant formula sold in China were investigated in comparison with human milk at different lactation stages. An amino acid analyzer was used to detect the contents of free and hydrolyzed amino acids in commercial infant formula, and total amino acid content and the proportion of individual amino acids were calculated. The results showed that free amino acids were detected in some of the 12 samples, while hydrolyzed amino acids were detected in all these samples. The average concentration of most amino acids was close to that of human milk at 1 to 60 d of lactation, and higher than that of human milk at 61 to 180 d. The average ratio of essential to total amino acids was 46.43%, which was close to that of human milk. The proportions of methionine and tryptophan to total amino acids were higher than those of human milk, the proportions of arginine and cystine to total amino acids were lower than those of human milk, and the proportion of other amino acids to total amino acids was close to that of human milk. This study reveals the difference in amino acid content between commercial infant formula and human milk.

The composition and content of amino acids in infant formula sold in China were investigated in comparison with human milk at different lactation stages. An amino acid analyzer was used to detect the contents of free and hydrolyzed amino acids in commercial infant formula, and total amino acid content and the proportion of individual amino acids were calculated. The results showed that free amino acids were detected in some of the 12 samples, while hydrolyzed amino acids were detected in all these samples. The average concentration of most amino acids was close to that of human milk at 1 to 60 d of lactation, and higher than that of human milk at 61 to 180 d. The average ratio of essential to total amino acids was 46.43%, which was close to that of human milk. The proportions of methionine and tryptophan to total amino acids were higher than those of human milk, the proportions of arginine and cystine to total amino acids were lower than those of human milk, and the proportion of other amino acids to total amino acids was close to that of human milk. This study reveals the difference in amino acid content between commercial infant formula and human milk.