The Effect of Autoclaving Lysine in the Presence of Carbohydrate on Its Utilization by the Chick* By

The value of heat treatment in improving the nutritive value of soy bean oil meal has long been known. More recently, however, the deleterious effect of autoclaving too long or at too high a temperature has been demonstrated (l-4). Evans and McGinnis (3) attributed this decrease in nutritive value caused by overheating to the lowered availability of methionine. Riesen et al. (5) in work with raw, heated, and overheated soy bean oil meal showed that for the amino acids studied the amount liberated by acid hydrolysis was unaffected by heat treatment, except for lysine, arginine, and tryptophan, and that the liberation of these three was decreased by prolonged heating. Clandinin et al. (6) supplemented a practical type of diet containing overheated soy bean oil meal with vitamins, methionine, and lysine, and produced growth comparable to that of chicks receiving properly cooked soy bean oil meal. Thus, overheated soy bean oil meal is apparently deficient in available lysine as well as in methionine. The lysine in proteins other than soy bean oil meal has been shown to be affected by heat treatment. Harris and Mattill (7) in work with kidney and liver tissue found that hot alcohol extraction produced no loss of nitrogen from the proteins but caused a decrease in the amino nitrogen. To explain this, they suggested the combination of free amino groups with other reactive groups, forming enzyme-resistant linkages. They further suggested that if the free amino groups in proteins are for the most part in lysine, slightly more than half of the e-amino groups of lysine disappear during hot alcohol extraction, possibly due to linkage with available carboxyl, imino, or hydroxyl groups. Greaves et al. (8), using rats, showed that casein heated for 30 minutes at 140’ was deficient in lysine. However, Block et al. (9) showed that the same amount of lysine could be isolated, chemically, from raw casein or casein which had been heated for 65 minutes at 150”. Zittle and Eldred (10) confirmed the work of Block et al. (9), finding that the lysine was chemically present but not released by enzymes.