International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The present manuscript describes some of the results obtained as part of a research contract investigating the effects of gamma irradiation on leather and library materials. Six samples of books and magazines, produced in Germany, the USA, and the former USSR between 1896 and 1962, were selected. All paper materials showed visible signs of biodeterioration and environmental damage. The samples were gamma-irradiated with a dose of 20 kGy using BULGAMMA radiation facility, based on the JS-850 60Co gamma irradiator at Sopharma AD, Bulgaria. The applied dose rate was 0.47 kGy/h. The effects of gamma irradiation were studied using thermogravimetric analysis. The results showed a 13% reduction in residual mass at 700 °C in the 1962 Soviet Union Newsletter, accompanied by a 3.6% decrease in the temperature (Tmax) at maximum weight loss rate. An 8.7% increase in residual mass at 700 °C was observed in the 1952 Reference Journal, and a 6.6% increase was measured in a German monograph from 1923. The study revealed that the effects of gamma radiation on paper structure depend on both the degree of prior damage and the type and composition of the paper.

Gamma radiation treatment for the destruction of biological pests is a widely applied method, due to its high efficiency, penetrating power of gamma rays, the ability to control the absorbed dose, speed and absence of toxic residual products. The application of gamma irradiation processing for preservation and conservation of artefacts made of wood requires knowledge of the possible radiation effects on the structure of its components and the selection of an appropriate absorbed dose and dose rate. Тhe present study is devoted to the side effects of gamma irradiation decontamination on the structure of two ebony woods dated to different radiocarbon ages. The changes induced by gamma irradiation at two dose rates: 0.037 Gy/s and 1 Gy/s with absorbed doses from 5 to 25 kGy using differential scanning calorimetry are presented. The effects of the absorbed dose, the dose rate and the age of the samples on the observed radiation effects are considered. Higher effects on the enthalpy of water loss were registered in the younger ebony wood after irradiation at low dose rate. Slight changes of the temperatures of water loss were found in the younger ebony wood sample. No significant changes in the temperatures of thermal decomposition in both ebony wood samples were measured.

The paper presents the applicability of gamma irradiation for the degradation of mycotoxins ochratoxin A, zearalenone and deoxynivalenol in wheat flour. The experiment was carried out by contamination of wheat flour samples with mixture of the mycotoxins and their gamma irradiaton with doses of 5 kGy, 10 kGy and 20 kGy using industrial gamma irradiation facility BULGAMMA. The concentrations of the mycotoxins before and after the radiation processing were measured by HPLC. The results showed that the application of a dose of 10 kGy resulted in incomplete decomposition of the investigated mycotoxins: 12 % of deoxynivalenol, 13 % of ochratoxin A and 37 % of zearalenone. The decomposition of the investigated mycotoxins in wheat flour achieved after gamma irradiation with a dose of 20 kGy was found to increase in the following order: ochratoxin A (48 %) > zearalenone (66 %) > deoxynivalenol (97 %).

The article presents the effects of different doses of gamma irradiation on the degradation of aflatoxins B1, B2, G1 and G2 in wheat flour. The experiment was conducted after contamination of wheat flour samples with mixture of aflatoxins with concentrations from 3 μg/kg to 12 μg/kg using reference material. Irradiation of flour aliquots with absorbed doses from 5.8 kGy to 27 kGy was carried out in an industrial gamma irradiation facility BULGAMMA. The concentrations of the aflatoxins before and after the radiation processing were measured by HPLC. The results showed that gamma irradiation with 27 kGy caused the highest degree of destruction of aflatoxins B2 (82 %) and G2 (81 %), followed by aflatoxin G1 (65 %) and to the lowest extend of aflatoxin B1 (59 %). Gamma irradiation with the maximum allowable dose for commercial food irradiation of 10 kGy was not sufficient to destroy the studied aflatoxins to the maximum permissible concentrations in wheat flour.