Quality Data |  |
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| The data for amino acids represent results obtained primarily by ion-exchange chromatography. Nutrient data for the following amino acids are included in the database:
Alanine (g), Arginine (g), Aspartic Acid (g), Cystine (g), Glutamic Acid (g), Glycine (g), Histidine (g), Isoleucine (g), Leucine (g), Lysine (g), Methionine (g), Phenylalanine (g), Proline (g), Serine (g), Threonine (g), Tyrosine (g), Tryptophan (g), Valine (g). Amino acid data for a class or species of food are aggregated to yield a set of values that serve as the pattern for calculating the amino acid profile of other similar foods. The amino acid values for the pattern are expressed on a per-gram-of-nitrogen basis. Amino acids are extracted in three groups-tryptophan, sulfur-containing amino acids (methionine and cystine), and all others. Tryptophan is determined by alkaline hydrolysis/HPLC (AOAC 988.15), methionine and cystine by performic oxidation/HPLC (AOAC 994.12) and all others by acid hydrolysis/HPLC (AOAC 982.30). The amino acid patterns and the total nitrogen content were used to calculate the levels of individual amino acids per 100 g of food, using the following formula: AAf = (AAn * Vp ) / Nf In the past, the number of data points appeared only on the food item for which the amino acid pattern was developed, not on other foods that used the same pattern. It referred to the number of observations used in developing the amino acid pattern for that food. For foods processed in the new NDBS, the number of observations used in developing an amino acid pattern will be released only with the pattern. The amino acid profiles calculated from these patterns will show the number of data points to be zero. If amino acid values are presented for an item with more than one protein-containing ingredient, the values may have been calculated on a per-gram-of-nitrogen basis from the amino acid patterns of the various protein-containing ingredients. Then the amino acid contents for an item on the 100-g basis were calculated as the sum of the amino acids in each protein-containing ingredient multiplied by total nitrogen in the item. |
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