Effects of gamma ray irradiation on pigment betanin (betacyanins and betaxanthins) and its influence on color of beta vulgaris

Radiation processing of food materials has been a subject of interest in recent years because of its ability to inactivate enzymes and destroy microorganisms. Radiation may, however, change the color, flavor, and texture and therefore the acceptability of a food. Its exact effect depends upon the food in question, the processing conditions and the total radiation dose employed. Use of heavy particle radiation like alpha, neutrons, protons and deuterons in food products must be excluded since they have the further property of bringing about nuclear transformation. Also, with these heavy particles at their normal energy levels, penetration is small. The gamma ray is not a particle. It is a non-corpuscular electromagnetic radiation of extremely short wavelength. It is similar to X-ray and is a highly penetrating ray. Hence, it has a tremendous possibility in pasteurization; as well as, in sterilization of foods. The potential value of radiation to food preservation is unlimited and hardly touched. A particular advantage of irradiation is that it does not appreciably raise the temperature of the food during the treatment. Thus perishable fruits and vegetables can be preserved in their fresh state. Betanin is the conspicuous pigment of the root. Beta vulgaris, comprised of red-violet group of pigments called betacyanins and the other yellow group of pigments known as betaxanthins (26). These two pigments occur in the cell sap (vacuoles) and thus belong to the cytochromes (113). When either of these two pigments occur alone, the pigmented part of the plant is either red-violet or yellow. They are also often found together and thus color of the pigmented part of the plant may vary from violet-red, red, fire red, orange-red, and orange to yellow, depending on the relative amounts of the two types of pigments (26). Several investigators have shown that the high level of irra-diation causes visible bleaching of fruits and vegetables. The intensity of the pigmentation in fruits and vegetables has an important relationship to the commercial value of irradiated products. This investigation was undertaken to study the effect of gamma radiation on the pigment betanin at and above the pasteurization dose levels; and its relative influence on color, ascorbic acid, enzymatic activity and histological structure.