Abstract
The experiments described below include (A) in vitro digestion experiments on irradiated and non-irradiated proteins with pepsin and trypsin respectively and (B) growth and metabolism studies on rats kept on low protein diets where the protein was either irradiated or non-irradiated.
A. In vitro Digestion Experiments on Irradiated and Non-irradiated Purified Proteins with Pepsin and Trypsin, Respectively. 1. Tryptic Digestion of Casein. The irradiated product was prepared by exposing dry casein (Merck according to Hammarsten) for 2 1/2 hours at a distance of 18 inches to the mercury quartz lamp in a current of air. The digestion experiments with irradiated and non-irradiated casein were carried out as described by Helmer. 1 At the end of the digestion period the undigested protein was precipitated and the refractive indices of the filtrates read.
As shown in Table I, the non-irradiated casein is somewhat better digested than the irradiated. The refractive index readings were confirmed by actual determination of nitrogen in the filtrates.
2. Peptic Digestion of Egg-White. Dried egg-albumin was prepared and digestion experiments carried out according to the method described by McMeekin and Freeland. 2 A portion of the dried, powdered material was irradiated for 4 hours in a current of air; the longer irradiation period being used because of the coarse physical state of the protein. Here again the amount of digestion was slightly greater for the non-irradiated protein than for the irradiated (Table II).
B. Growth and Metabolism Studies on Rats Kept on Diets Low in Irradiated and Non-irradiated Proteins. 1. Group Experiments. In spite of the very slight differences in digestibility between the irradiated and non-irradiated proteins, the final test of actual feeding experiments was obviously the next step.
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