The reaction or reactions between proteins and carbohydrates involving non-enzymatic browning o r discoloration of foods during processing and storage has been referred to as the Maillard reaction, protein-sugar reaction, or carbonyl-amino reaction (reviewed by Hodge, 5 ) . A decrease in nutritive value resulting from such reactions has been attributed chiefly to creation of lysine deficiency (reviewed b y Patton, 10). Under certain circumstances it has been found that a portion of the lysine is not recoverable by acid hydrolysis of the treated protein, and this portion is said to have been "destroyed. " However, evidence for lysine destruction in proteins must be regarded as circumstantial, because the '' destroyed" lysine has never been measured directly. Moreover, the determination of the remaining lysine in such an environment has presented a difficult analytical problem. Microbiologic assay, the principal method hitherto employed, is particularly objectionable, because it involves additional browning reaction when the hydrolysate is autoclaved with glucose prior to inoculation, and because it is subject to errors of specificity.The present work resulted from a search for a new and better analytical tool for measuring such amino acid destruction. This approach began in 1948 when Patton, Hill, and Foreman (13) chromatographed each of the dietary-essential amino acids, before and after heating with glucose, and observed that lesser amounts of certain of the amino acids remained after browning. This was followed by several years of research on the methodology of paper migration analysis (12, 1 4 ) , resulting in modifications of the maximal density method of Block ( l ) , and of the area method of Bull, Hahn, and Baptist ( 2 ) . The authors are not aware of any publication in which a similar application of quantitative paper chromatography has been reported.Certain observations of Lea and co-workers (reviewed by Hodge, 5 ) are especially pertinent to the present report. They found no destruction of lysine from acid hydrolysis in the presence of added glucose. A t 37°C. (98.6"F.), they found the most rapid and extensive reaction to occur in a state of incipient dryness (6). By use of the Sanger technique (15), they demonstrated the principal points of attack on the lysine residues to be the epsilon-amino groups, and a small amount of alpha-amino groups contained on a few terminal lysyl residues (16).Free amino acids were studied by dissolving 100 mg. of each chromatographicallypure amino acid in 25 ml. of 5% chromatographicallypure anhydrous mglucose solution.From this volume, a 10-ml. aliquot was transferred to a small beaker, and evaporated t o a concentrated syrup on a water bath a t 9OoC. (194"F.). Each sample was then autoclaved 2 hrs. (moist heat). The resulting samples were then diluted with water to 10 ml. a t room temperature, and chromatographed alongside the unbrowned aliquots t o obtain comparative increment-curve areas for both the amino acid aad glucose ( 2 ) .Casein was subjected to a number of dif...