Effects Of Electron Beam-line Irradiation On Insecticide/Bactericidal And Wheat Quality

Tilletia Cntroversa Kuhn (TCK) is the most important quarantine bacteria in imported grain of our country. To carry out green grain storage technology, protect environment and to ensure food safety in China has become an important strategic significance. Pesticides /bactericidal by electron beam irradiation technology is promised to play an important role not only in quarantine TCK bacteria in imported wheat but also for non-chemical control of pests in stored grain, especially for the grain storage in South China region with high temperature and humidity. The effectiveness of EB irradiation on-line to kill insects and bacteria dynamically were studied, effects on wheat quality were also included in this study. The main results are as follows:In the experimental design of two doses (0.3kGy, 0.6kGy), the electron beam on line can effectively kill pests in stored grain. In view of the biochemical effects of radiation, the insects died gradually in 7 days instead of immediately on the spot. Sitophilas Oryzae (L.) adults are more sensitive to the electron beam irradiation than that of Rhizopertha Dominica (F.). The range of 0.3~0.6kGy dynamic EB irradiation as a reference dose for insecticide is realistic. 0.6kGy dose of radiation are all death capacity to the test insect species and eggs. In the study of on-line irradiating sterilization experiments, EB irradiation can effectively inhibit the total number of stored wheat colony(P<0.01), the higher the radiation dose, the lower the total number of colonies. Different doses of irradiation were all highly significant inhibited to all species of fungus in this study. The sensitivity order to EB irradiation of fungus is Alternaria sp>Aspergillus> Fusarium> Penicillium> Rhizopus.In the study, the method of artificial inoculation TCK spores to affect wheat was used to study the effectiveness of online EB irradiation to kill TCK. It was found that EB irradiation can inhibit the germination of TCK spores and made them inactivation, the higher dose, the lower germination. The number of TCK spores germination was reduced with abnormal germinating or growing-stopped until the full suspension of germination, which reflected the radiation sensitivity of TCK. 3.6kGy dose of EB irradiation could inhibit and inactivate the winter TCK spores; the death rate of TCK was reduced by 90% or more with 4.0kGy on-line irradiation; wheat can not be disseminated in the dose of 4.4kGy.EB irradiation of wheat seed germination test results showed that, 0.5 ~ 5.1kGy EB irradiation inhibited the germination of wheat seeds, the higher the radiation dose, the more severe inhibition of seed germination.Radiation dose is the most significant to the vitality index. Water is essentially the same, color, odor testing were normal. Determination of membrane permeability of the seed showed that electron beam irradiation can lead to seed damage, increased membrane permeability.EB irradiation dose was negatively correlated with falling number, gluten index and falling number of sample changed significantly especially after radiation doses above 4kGy.Dough rheological properties from the Farinograph curve showed that, comparing with the control, absorption, stability, break time and other indicators of samples in each dose level of EB radiation were increased in varying degrees with doses. Evaluation value is negatively correlated with the degree of softening, and other water absorption, development time did not change very obviously.The quality of steamed bread made from 1.0kGy irradiated wheat is still normal while minor changes happened in the dose of 3.5 kGy, but it is still in the part of the normal range of consumption. When dose is higher than 3.8 kGy, the eating quality of steam bread became accelerated deterioration. TPA spectrum analysis showed that the quality indicators of bread as hardness, adhesion, elasticity, cohesiveness, chewiness, resilience were significantly correlated (P<0.01), while the EB irradiation doses were also significantly associated with all above bread quality indicators (P<0.05).EB irradiation can partially damaged starch granules in wheat flour and the damaged starch content increased with the increase of irradiation dose. DSC research results showed that the radiation dose affected the thermal properties of wheat starch significantly. Molecular weight study of wheat starch showed that wheat starch molecular weight were reduced after irradiation, and when the radiation dose is about to 4.4 kGy, the molecular weight reduced nearly an order of magnitude lower. Thus further explained that, the essence of rheological properties changes in wheat starch which also affected changes in processing products are the results of starch molecular structure changes because of EB irradiation.SDS-PAGE electrophoresis and RP-HPLC studies found that the molecular weight and proportion of protein units in gliadin were not particularly significant changed by EB irradiation, only ratio ofα/βsubunit slightly increased. The peak of the CD spectrum for EB irradiated-gliadin is in red shift and the absorption of light values increased with EB irradiation doses. It shows that under the conditions of the experimental doses, macromolecules in gliadin had been partially degraded while Low molecular weight glutenin subunits(LMW-GS)were decreased greatly, the higher doses, the more influence.