Radiation Chemistry of Foods

Part I. Reaction Rate Constants of Some Foods Constituents with Hydrated Electrons and Hydroxyl Radicals

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In food irradiation, water-soluble food constituents undergo the attack of e_??_ and OH at the neutral region.
Reaction rate constants of some food constituents with eaq and OH were measured by competition methods using nitrous oxide and ³H-formate as competitors, respectively. High selectivity was observed among the reactions with e_??_ and the e_??_-reaction rate constants are 10¹⁰ M^-1sec^-1 (cysteine), 10⁹M^-1sec^-1 (methionine, ascorbic acid, and histidine), and much smaller (sugars, and the other types of amino acids). The OH-reaction rate constants range from 10⁹M^-1 sec^-1 (cysteine, histidine, methionine, aromatic amino acids, and ascorbic acid) to 10⁸M^-1sec^-1 (sugars and the other amino acids), indicating that the reactions with OH are less selective. Selective destructions of cysteine and ascorbic acid in food irradia-tion may be partly ascribed to their selective reactivities with some less reactive species which are produced by reactions of e_??_ or OH with oxygen or the other constituents as well as their higher reactivity with e_??_.