Studies On Degradation Of Fishery Drugs And Quality In Muscle Of Grass Carp By ⁶⁰Co-γ Irradiation

Irradiation is one of the most efficient technological processes due to its advantages of less heating, penetrating power, low energy consumption and convenient in effective sterilization and degradation of drug residues. The objective of the research is to study the degradation effects of five fishery drugs and the change of quality of grass carp muscle by 60Co y-ray irradiation. The irradiation degradation rates on fisher drugs and the radiolysis products and the changes of quality of grass carp muscle were investigated. The main projects and research results are as follows:(1)Study on the degradation rate of fishery drugs of the irradiation dose, the initial concentration and environmental conditions. The results demonstrated that fishery drugs can be degraded by irradiation. The degradation rate had a positive correlation with the irradiation dose and a negative correlation with the initial concentration. Treated with 2kGy of 60Co-y-irradiation, the degradation rates of five fishery drugs at the concentration of 20mg/L were above 85%.The degradation rates of five fishery drugs (sulfamethazine, oxolinic acid, chloramphenicol, furazolidone, oxytetracycline) at the concentration of 100mg/L were 49.76%,63.08%,26.98%,22.19%,95.97%,respectly. The degradation rate of the five fishery drugs was above 90% at the dose of 8kGy. The effects of acid/base and degassing environments, temperature and additives on the degradation of fishery drugs were notable. Lower temperature, proteins, lipids, carbohydrates and inorganic compound will inhibit the degradation of fishery drugs in aqueous solution. The degradiation of fishery drugs can be affected much more of composition of grass carp muscle than aqueous.(2) Study on the degradation products of fishery drugs by irradiation. When treated by irradiation, the chloramphenicol were decomposed to the degradation products with molecular weights 588,475,362,419,375,362,329,315 Da. The molecular weights of sulfamethazine degradation products were 475,295,362,279,362,227 Da. The molecular weights of oxytetracycline degradation products were 476,227,272,341,386,454,476,567,589,68.0,461,397,417,439,400,440,391 Da. The molecular weights of oxolinic acid degradation products were 141,387,248,376 Da. The molecular weights of furazolidone degradation products were 248,259,454,294,348,162 Da.(3)Study on the quality of grass carp muscle by irradiation. The content of protein, fat, carbohydrate and ash of grass carp muscle were not changed by irradiation except for a decrease of moisture content. There is no significant change in fatty acid composition by irradiation. Irradiation dose of 8kGy produced significant reduction of bacteria from 1.12×106 cfu/g to 30 cfu/g. There is no detectable effect on water holding capacity, but pH has decreased slightly by irradiation. The radiation can cause protein degradation and fat oxidation of grass carp muscle resulting in an increase in TVB-N and TBA values.(4) Study on the volatile compounds of grass carp muscle by irradiation. Results showed that 67 volatile compounds were identified from the muscles prior and after irradiation. The kinds and contents of aldehydes,alcohols, hydrocarbons and ketones were significantly changed markedly after irradiation. Some amines and sulfur compounds were detected in 8-10kGy. Their combination effects were responsible for the flavor changes of radiated grass carp, even produced some off-flavor.