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The total amino acid profile of a food protein expressed in relation to some standard is a good indicator of the potential nutritive value, but it may at times be misleading if one or more of the essential amino acids are only partially available. If this is true, the "actual" nutritive value of the protein will be less than its "predicted" value, obtained from its amino acid profile. It is therefore critical that the availability of the reactive, but most frequently limiting essential amino acids, Iysine, methionine, and cystine,* be known. This is especially true for proteins present in processed foods and food ingredients.
Before amino acid data, whether "available" or "total," can be used as indicators of potential nutritional value, they must be expressed in relation to some reference standard. Such standards and the calculation of amino acid score are discussed in detail in the following chapter.
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