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( Lixia Wang ),( In-lee Choi ),( Joo-hwan Lee ),( Ho-min Kang ) 한국농업기계학회 2019 한국농업기계학회 학술발표논문집 Vol.24 No.1
Asparagus is vulnerable to thrips that is the major insect pest of asparagus. The effect of high carbon dioxide pretreatment (60%CO2, v/v) for killing thrips on asparagus sensory quality, physiological and biochemical changes during postharvest storage was investigated. After 60% of CO<sub>2</sub> pretreatments for 24h(CO<sub>2</sub>24h) at ambient temperature or for 48h(48h) or 72h(72h) at 4°C, the asparagus were stored in MA package (10,000 cc/m²ㆍdayㆍatm oxygen transmission rate film) and non-MA package (perforated film) at 4°C for 30 and 25 days. In all treatments, MA package obtained 5 days longer shelf life than non-MA package. Irrespective of the duration, CO<sub>2</sub>24h was worst in non-MA package but 72h in MA package with highest fresh weight loss rate. The O<sub>2</sub> and CO<sub>2</sub> content was similar in all packages, nearly 19-21% and 6-11% respectively. The ethylene content was little affected in CO<sub>2</sub>24h, but lower at 4°C. In MA packages, the concentration of ethylene was nearly 1ppm whereas was 2ppm in non-MA package in the end. The best visual quality was obtained in 48h MA packages which kept the marketability that determined by the score≥3, and the worst was the control(air) 24h in non-MA packages. The off-odor was similar with the visual quality, and lower temperature inhibited the odor, it indicates that the temperature and duration of CO<sub>2</sub> pretreatment affect asparagus sensory quality during the postharvest storage. It is worth noted that control 60h has the lowest firmness in tip and stem of spear in MA packages, and 60% CO<sub>2</sub> increased the firmness. The CO<sub>2</sub> pretreatments retarded hue angle decrease which related to duration in tip but not in stem. CO<sub>2</sub> pretreatments were obviously reduced the soluble solids content at 4°C and ambient temperature and the lowest was CO<sub>2</sub>24h and the highest was 48h. The electrolyte leakage was less in CO<sub>2</sub> pretreatments in MA packages. In conclusion, the effect of high CO<sub>2</sub> pretreatments on asparagus was depended on the duration and temperature, 48h in MA package was better in keeping the sensory quality physiological and biochemical characteristics.
DeNOx performance and characteristic study for transition metals doped iron based catalysts
Lin Zhu,Zhaoping Zhong,Han Yang,Chunhua Wang,LixiaWang 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4
Novel, environmentally-benign catalysts for selective catalytic reduction of NOx were prepared by citric method through introducing transition metal elements (Ce, Cu and Co) into iron oxide. The physical-chemical properties of different catalysts were investigated by the characterization technologies like N2-physisorption, XRD, NH3/NOTPD and H2-TPR. The results indicated that the introduction of transition metal elements increased the specific surface area and adsorption ability for reactants (NH3 and NOx). The redox capacity for the doped catalysts was improved at the same time. These characteristics all contributed to the improvement of catalytic performance. The CoFeOx catalyst exhibited the widest temperature window for SCR reaction, and the CeFeOx catalyst showed the most obvious decline of NOx conversion with the elevation of temperature above 250 oC. Water vapor inhibited the SCR activity at low temperatures and relieved the decline of NOx conversion at higher temperatures. Meanwhile, the formation of N2O was inhibited. The pretreatment of SO2 leaded to the sulfation of the active species for different catalysts. The decline of redox capacity and the reduction of active nitrate adsorbed species accounted for the serious loss of SCR activity at low temperatures. The abundant surface acid sites brought by the sulfation process might be the main reason for good SCR activity in the medium temperature range.