The Loss of Added Lysine and Threonine During the Baking of Wheat Bread

Abstract
Rat growth experiments and microbiological assay methods were used to estimate the loss of added free L‐lysine·HCl and DL‐threonine during the baking of wheat bread. Introductory rat experiments showed that the optimum concentration for growth of L‐lysine. HCl added before baking was approximately 0.40‐0.45% of the fresh weight of the flour. The optimum concentrations of L‐lysine·HCl and DL‐threonine when added together were approximately 0.55% for the former amino acid and 0.30% for the latter. The loss of added L‐lysine·HCl during baking was found to be 10–15% as estimated by animal experiments and 5–10% as estimated by microbiological assays. The loss of L‐threonine (added as DL‐threonine) was significantly greater, amounting to approximately 40% as judged by the feeding trials and 20–25% according to the microbiological estimations.The amino acid compositions of the flour and the bread baked from the flour were also determined.

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