No abstract

1% carrageenan oligosaccharide solutions obtained by electron beam irradiation at the radiation doses of 9 kGy (CO-9) and 30 kGy (CO-30) were applied for shrimps before frozen, and their effects on quality of frozen shrimps were investigated by observing the microstructure of shrimp’s muscle tissue, measuring their weight loss (%), hardness and pH after thawing. Comparison with the shrimps treated by 1% tetrasodium pyrophosphate solution (Na4P2O7, positive control) and distilled water (negative control), the shrimp samples soaked in CO before frozen kept their initial properties, and the shrimps treated by CO-30 solution showed better quality than others after 3 weeks of frozen storage. Specifically, the mean distances of muscle bundles and muscle fibers in the shrimps soaked in CO-30 solution were 23.9 µm and 11.1 µm, respectively, much smaller than 37.9 µm and 14.8 µm in the shrimps treated by Na4P2O7, and 46.7 µm and 19.8 µm in the shrimps soaked in distilled water only. Our results also revealed that the weight loss after thawing and pH of the shrimps soaked in CO-30 solution were 1.55% and 6.40, much lower than that of the positive control sample (2.59% and 6.82) and negative control sample (4.83% and 6.58), respectively. In contrast, the mean of hardness of the sample soaked in CO-30 solution was 20.4, about 20.7 and 36.0% higher than those of positive control (16.9) and negative control (15.0). These results suggested that CO-30 is effective to inhibit the denaturation of shrimp during frozen storage and can be applied to prolong the shelf life and keep the quality of frozen shrimp products.

Lasiodiplodia theobromae causes decay of star apple fruits (Chrysophyllum cainino) during harvest, transport and storage. If the irradiation dose is higher than 800 Gy, this mold will be controlled. However, the quality of star apple was significantly changed when they were irradiated at the dose higher than 0.6 kGy by electron beam (EB). To keep irradiation dose under 0.6kGy, the synergic effect of the combined treatment of EB irradiation and sodium dichloroisocyanurate (NaDCC) was investigated. In this study, star apples were pretreated with NaDCC concentrations in range of 10 -70 ppm in order to decrease the growth of mold and extend the shelf-life of treated star apples. The results showed that pretreatment with 20 ppm NaDCC had also kept the color and reduced disease of stored star apple. Dipping star apples into 20 ppm NaDCC solution before irradiating at 400 Gy and 600 Gy could be chosen as the best way to inhibit the development of Lasiodiplodia theobromae and extend the shelf life of star apple in the trading condition (7 days, 9oC).

Vietnamese graphite powder was irradiated by electron beam radiation (EB) at a range of dose from 0 to 120 kGy, then the graphite samples were expanded with a mixture of H2O2:H2SO4 (1,4:20, v/v) incorporating microwave treatment at 700 W for 30 seconds. The characteristic properties of graphite before and after expansion were evaluated by methods of FTIR, Raman, SEM and XRD. Besides the self-assembled of the graphite’s structure after irradiation, the electron beam radiation also facilitated intercalation processing to make expanded graphite, with coefficient of expansion (Kv) 35% higher than that of pristine graphite.

Reduction of graphene oxide (GO) for preparing the reduced graphene oxide (rGO) by γ–ray irradiation was investigated. GO was dispersed in the ethanol solution with the GO concentration of 1 mg/ml, then irradiated with γ–ray in presence of oxygen at dose range of 0 – 100 kGy for preparation of rGO product. The characteristic properties of GO and rGO were determined by UV-Vis spectroscopy, X–ray diffraction (XRD), Transmission Electron Microscopy (TEM), contact angle measurement and test of water desalination. The result showed that water desalination efficiency of rGO was about 46 – 48%.