Abstract
IT is now sixty years age since it was first discovered that bacteria are killed by exposure to sunlight, and that the bactericidal effect is due to rays of short wave-length. For medical purposes the use of such ultra-violet rays is now well known, but it is not generally known to what extent irradiation is used commercially in the preparation of foodstuffs, and the engineering devices that are employed for obtaining the ultra-violet rays. Until recently, sterilization of water by ultra-violet radiation has been hampered by the complexity of the equipment available (Elect. Rev., Sept. 23). Recently, Messrs. Hanovia, Ltd., have brought out the new ‘Uster’ type of sterilizer, which uses a simple straight generating quartz mercury are tube with a 700-watt loading. This starts automatically by an electronic discharge from activated metal electrodes. One of these units can deal with 600 gallons of fluid per hour. Mr. Harding, a director of E. Harding and Sons, Birmingham, states that in a bakery he finds that dough which has been subjected to ultra-violet rays during the seven to ten minutes it is mixing not only gives a loaf a better colour, owing to the slight bleaching action of the rays, but also causes a definite improvement in fermentation. Another application of ultra-violet radiation is to determine quality or age by fluorescent effects. Many substances absorb ultra-violet rays and re-emit them as visible light of certain colours. The colours are specific and characteristic for each substance, but minute differences in chemical composition often cause large differences in the colours of the emitted light. An egg, for example, changes its colour from mauve-red owhen it is newly laid to pale blue as it grows older, and a mixture of margarine and butter appears an unmistakably different colour from pure butter.
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Commercial Irradiation of Food. Nature 144, 746–747 (1939). https://doi.org/10.1038/144746c0
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DOI: https://doi.org/10.1038/144746c0