Friedman M, Gumbmann M R, Ziderman I I
J Nutr. 1987 Mar;117(3):508-18. doi: 10.1093/jn/117.3.508.
When a nutritionally complete basal diet containing 10% protein from casein was supplemented with 20% protein from unheated casein, wheat gluten or soy protein isolate, weanling mice exhibited significantly increased weight gains. In contrast, weight gains were markedly reduced compared to those with the basal diet; that is, growth was inhibited, when the supplement was soy protein or gluten that had been heated at 200 or 215 degrees C for 72 min in the dry state to stimulate crust baking. Addition of various carbohydrates to the gluten during heating prevented such growth inhibition. After heating with sodium ascorbate (but not L-ascorbic acid), soy protein (at 200 degrees C) and gluten (at 215 degrees C) completely prevented growth when added to the basal diet. Growth inhibition also occurred with a heated casein-ascorbate mixture, but was less than with the other proteins. The extent of growth inhibition increased sharply with temperature of heating in the range 180-215 degrees C and with sodium ascorbate concentration in the range 1-20%. Possible physical and chemical changes during heating of protein-ascorbate mixtures are discussed, as are possible mechanisms for the growth inhibition.
