Application of gamma irradiation technique for the preservation of propolis

Irradiation has been recognized as an efficient method for the reduction of deteriorating and pathogenic microorganisms in foods. Propolis is a resinous product made by bees from material processed by the bee's own metabolism and resins from plants. The aim of this work was the application of gamma irradiation technique for the preservation of propolis, because of its efficiency in the reduction of the microbial load. The changes on the total flavonoids content, phenolic compounds and other characteristics required for the qualification and characterization of Brazilian propolis were also analysed. Propolis samples from Juiz de Fora region, Minas Gerais, were irradiated in a 60Co source, with doses from 0 to 10kGy for the microbiological analyses and 5.0, 7.0 and 10.0kGy for the physico-chemical analyses. The physico-chemical that have been made were: determination of total flavonoids content, semi-quantitative determination of phenolic compounds (artepelin-C, kempferol, chrysin, galangin and quercetin), dry matter analysis, humidity, ash content, mechanical mass and waxes. The ionizing radiation has shown to be efficient in the reduction of the microbial load. Total coliforms determination showed a great reduction with the dose of 3kGy and concerning mesophile aerobic bacteria a systematic reduction was observed, achieving values <10 UFC/g for the dose of 10kGy; similar results was obtained for molds and yeasts. Salmonella assays were negative for all samples. There was no significant alteration on total flavonoids contents nor on the composition of phenolic compounds as a consequence of radiation application at the assayed conditions. The complementary analyses of dry matter and humidity contents, ashes, mechanical mass and waxes did not shown changes after irradiation even with the maximum dose of 10kGy, remaining the results within the standards required by the Brazilian legislation. (author)