The quality of the protein in germ and milk breads as shown by the growth of weanling rats: The significance of the lysine content

Abstract

AbstractBy calculation from data obtained previously, on the growth rate of weanling rats on diets containing white bread as the source of protein supplemented with different amounts of L‐lysine, it is now shown that the mean rate of growth is directly proportional to the mean intake of lysine. This applies when the protein content of the diet is 12–13% and the amounts of lysine added are within the range 0–0.25% of the diet. Under these conditions the rate of growth y (g./rat/day) is related to the intake of lysine x (mg./rat/day) by the empirical equation y = 0.06154x + 0.03. Growth rates on bread containing (a) wheat germ, (b) skim milk powder, and on bread crust have been measured, and the applicability of the equation to these data has been examined. On bread crust the rate of growth was significantly less than on bread crumb. When the observed growth rates were substituted in the empirical equation the calculated lysine content of the crust indicated a loss of available lysine compared with the crumb of about 20%. The observed rates of growth were comparable with the growth rates calculated from the lysine contents of bread containing added raw wheat germ. Heat processing of the raw wheat germ gave slightly lower rates of growth and food consumption, suggesting a small reduction in available lysine due to the processing. Similar results were obtained with bread prepared with dried milk powders (6% of flour weight).