CONTENT OF NONPROTEIN TRYPTOPHAN IN HUMAN-MILK, BOVINE-MILK AND MILK-BASED AND SOY-BASED FORMULAS

Variations in the content of total non-protein (protein-bound + free) and free tryptophan in human and bovine milk after delivery, soy 'milk', and adapted formulas based on bovine milk and soybean protein are reported. Colostrum contains much more of both forms of non-protein tryptophan than mature human milk and bovine milk, and the percentage of free tryptophan is also higher in human milk. Fresh commercially available bovine milk contains amounts of non-protein tryptophan similar to those of bovine milk 1 month after delivery. However, these levels are much lower than those observed in soy Both forms of non-protein tryptophan are also much higher in soybean than in bovine milk formulas, although there are some differences among the kinds of formulas. However, values are significantly lower than in colostrum. The differences in the content of non-protein tryptophan are discussed.