The Effect of Heat Treatment of Milk Feedings on the Mineral Metabolism of Infants.*

It has been observed that, young rats fed long heat-treated milks*evaporated, condensed, and pasteurized by the “hold” process-fail to grow normally, the degree of stunting being proportional to the length of time of heating rather than to the temperature employed. For example, rats fed milk pasteurized by the “hold” process made only about half their normal growth; whereas, those fed milk pasteurized by the “flash” method, or quickly boiled, grew quite normally. Animals fed evaporated milk made scarcely any growth, while with those on the sweetened condensed milk, growth was comparable to that on milk pasteurized by the “hold” process. The nutritive failures in all cases appear to be due to the fact that during the process of heating, the calcium salts are thrown more or less out of solution and thus made less readily available to the animals, by adhering to the sides and bottom of the containers, or by more complete precipitation, most noticeable in evaporated milks. When care was taken to incorporate the precipitated calcium salts into the various milks by suspension in a starch paste, growth was normal. In the investigation there is nothing to indicate whether the result’s were due to a readjustment in the calcium, a change from the monoand diphosphate to the triphosphate, or to a change in the colloid structure of the milk.2 It is conceivable that slight losses in the calcium content of cow’s milk subjected to various methods of heat treatment may