I. Some After-Effects in Fats Irradiated with High-Energy Electrons and X Rays

Two types of chemical after-effects have been observed in fats irradiated with high-energy cathode rays and soft X rays. The first is the well-known autoxidation chain reaction which develops much more rapidly than before irradiation. Destruction of natural antioxidants in the fat is probably responsible. The second effect occurs preferentially at −20°C to −30°C and is due to a reaction between oxygen and a reactive group which is stable at these temperatures but becomes unstable with increase of temperature and softening of the fat; apparent peroxides and other reactive groups develop and the susceptibility to autoxidation increases. This effect can occur to some extent at physiological temperature in hard fats. This work has been carried out with the co-operation of the Medical Research Council as part of the programme of the Food Investigation Organisation of the Department of Scientific and Industrial Research. We wish to express our gratitude to Mr. J. W. Boag and Mr. D.Moore for carrying out the irradiations with high-energy electrons at the Radiotherapeutic Research Unit of the Medical Research Council, Hammersmith Hospital, to Professor J. S. Mitchell for permission to use the 50 kV X-ray generator in the Department of Radiotherapeutics, Cambridge University, and to Dr. C. H. Lea for many helpful discussions. Crown copyright reserved.