A novel method of shrimp blanching by CO2 heat pump: Quality,energy, and economy analysis

To reduce the energy consumption of the shrimp blanching process and improve the economic value of the blanched product, a transcritical CO₂ heat pump blanching system (THPB system) was designed in this paper. The trends of astaxanthin were investigated at atmospheric pressure near boiling temperature, combined with the color and structural properties of shrimp samples, and the optimal blanching times of 270 s and 240 s were obtained at 90°C and 95°C, respectively. In contrast to the fuel blanching system (FB system) at 100°C, the annual standard coal consumption of the THPB system with 90°C blanching is decreased by 79%, and the annual operating cost can be saved by CNY 63,800, with a payback period of about 3.13 years.Industrial relevanceBlanching is one of the effective ways to prolong the shelf life of shrimp. However, the research on the blanching time and temperature of shrimp is not comprehensive. In addition, the traditional fuel blanching process has high energy consumption and pollution, and can no longer meet the quality requirements of the modern food processing industry. Heat pump has been shown to have better performance in food drying, but it is less used in blanching. The information presented in this study may provide other insights into food processing.     

Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)

The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.     

紫色马铃薯酒发酵工艺优化及主发酵期花青素与色泽的动态变化

以紫色马铃薯为原料，在单因素的基础上，通过响应面法对紫色马铃薯酒的发酵工艺参数进行优化。最佳发酵工艺参数为:马铃薯与面粉比1:0.6、料水比1:1 (g/mL)、α-淀粉酶添加量8.5 U/g、酒曲添加量0.45%。此工艺在28 ℃下发酵14 d，得到的紫色马铃薯酒酒精度13.5%vol，花青素含量166.34 mg/mL，酒体澄清透明呈紫红色，酸甜适中，有独特酒香，综合感官评定得分90分。测定主发酵期花青素和色泽的动态变化，分析表明，紫色马铃薯酒在发酵过程中花青素呈现先上升后下降的趋势，色度呈现先下降后趋于平缓的趋势，色调则与之相反。聚合色度和褐变指数总体均呈现逐渐上升的趋势。试验结果为工业化生产紫色马铃薯酒提供理论依据。     

Effect of in-app components,medium, and screen size of electronic textbooks on reading performance,behavior, and perception

Although many app-based textbooks are available for students, reading have not been thoroughly outlined. This study aimed to understand how changes from paper to electronic textbooks have affected the academic reading task, investigate student users’ perceptions of in-app components and screen sizes, and identify issues affecting in-app components and task requirements. A mixed factorial design experiment was employed. Results showed that there were no significant changes in comprehension and time spent reading between print text and the iPad. Yet, student highlighting, notetaking, and reading behavior and perception significantly changed based on condition. In addition, students struggled to use in-app components and found them frustrating especially when accounting for sentence splitting. The findings presented can assist in understanding the changes in student reading behavior, which can be used to improve interface design of future e-textbooks.     

Improving storability,physiological disorders,and antioxidant properties of ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) by pre-harvest 1-methylcyclopropene spraying

Ethylene continues to be a major factor influencing quality of European pears during storage. Although research has been done on the effect of pre-harvest 1-methylcyclopropene (1-MCP) on physiological characteristics in pears, a full understanding of cultivar response and antioxidant metabolism remains elusive. Spraying 1-MCP on ‘Bartlett’ and ‘d’Anjou’ pears was studied with respect to physiology, storage and eating quality, disorders, and antioxidant properties at two harvest date (H1 and H2) during storage and ripening. Treatment with 1-MCP extended the harvest window of ‘Bartlett’ and ‘d’Anjou’ pears 3 and 4 days, respectively, without reducing storage or eating quality. Treatment with 1-MCP reduced ethylene production (EPR) and respiration rates (RR), maintained fruit firmness and green colour during storage and retarded development of desirable melting texture in both cultivars. Additionally, 1-MCP lowered the incidence of disorders by alleviating membrane lipid peroxidation, retaining high total flavonoids (TF) and antioxidant capacity, and enhancing superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity in both cultivars. Overall, pre-harvest 1-MCP applications could extend storage time of ‘Bartlett’ and ‘d’Anjou’ pears to 5 and 6 months, respectively, at −1.1 ± 0.5 °C, by reducing ethylene synthesis and enhancing antioxidant metabolism.     

赤霉素GA3对小鼠机体氧化-抗氧化系统平衡的影响

选择昆明种小鼠为试验动物,以超氧化物歧化酶、谷胱苷肽过氧化物酶活性及丙二醛含量为观察指标,研究赤霉素GA3在剂量（197,394和788 mg/kg）暴露条件下,小鼠脾脏、肝脏和心脏组织是否发生氧化应激.结果表明,394和788 mg/kg每千克体重bw剂量组脾脏超氧化物歧化酶、谷胱苷肽过氧化物酶活性有所下降,与对照组相比,分别降低了21.01%,29.02%和23.36%,35.03%,与对照组相比差异显著;肝脏超氧化物歧化酶、谷胱苷肽过氧化物酶活性分别降低了9.01%,13.05%和12.81%,16.17%,与对照组相比差异显著（P〈0.05,P〈0.01）.同时赤霉素GA3处理后丙二醛含量显著升高,394,788 mg/kg bw剂量处理组脾脏和肝脏分别升高了19.06%,23.61%和22.33%,26.39%,与对照组相比差异显著（P〈0.05,P〈0.01）;肾脏超氧化物歧化酶、谷胱苷肽过氧化物酶活性有所上升,与对照组相比,分别上升了22.34%和40.20%,丙二醛含量有所下降,与对照组相比分别下降了35.93%和30.05%;另外,赤霉素GA3处理后,对心脏的氧化应激作用与对照组相比差异不显著.表明赤霉素对小鼠不同组织器官的氧化应激表现不同,对肝脏、脾脏有氧化损伤作用,对心脏作用不明显.     

氮化硅陶瓷超塑拉深成形规律研究

以非晶氮化硅纳米陶瓷粉体为初始材料,以纳米氧化钇和氧化铝为助剂液相烧结获得超塑性陶瓷块体材料,在1550℃的低温条件下,实现氮化硅陶瓷的超塑性成形。利用描述超塑性材料的Backofen方程,建立陶瓷超塑性成形的刚粘塑性有限元模型,并与实验研究相结合,研究氮化硅陶瓷在不同条件下超塑性拉深成形过程中,成形体径向和厚度方向的尺寸变化,得到了氮化硅陶瓷超塑性拉深成形过程厚度和径向尺寸改变的基本规律。     

Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study

The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richard's equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes.     

擦窗机悬挂轨道三维结构有限元分析

为探究某擦窗机悬挂结构的合理性,在AIP中创建其悬挂轨道的三维参数化特征模型,并根据轨道的结构、材料和特定工况受力等边界条件,建立悬挂系统的有限元模型,模拟计算2种有代表性的偏栽荷工况受力情况,得到悬挂轨道的三维应力分布、结构变形和安全因数．根据工程设计要求和初步分析结果,在保持边界条件和载荷条件不变的情况下,快速更新轨道结构参数,并通过比较分析确定塔楼悬挂轨道的最佳断面参数．该轨道及其固定间距、滑车滚轮和导向轮等构件均满足设计安全要求．     

Macaroon-like FeCo2O4 modified activated carbon anode for enhancing power generation in direct glucose fuel cell

Macaroon-like FeCo₂O₄ nanomaterial was prepared and used as electrocatalyst in direct glucose alkaline fuel cell (DGAFC), which exhibited high catalytic activity towards glucose oxidation reaction. Maximum power density of 35.91 W m⁻² was achieved in the DGAFC equipped with a FeCo₂O₄ modified activated carbon (AC) anode, which was almost 151% higher than the control. Physical and electrochemical characterizations were performed to provide further understanding of the origin of its high activity. Our results show that the introduction of FeCo₂O₄ into the AC anode remarkably increase the exchange current density and reduce the charge transfer resistance. It is supposed that there is a synergistic effect between Fe (III) and Co (III), which accelerates electron transfer from glucose to external circuits. This study will promote the development of cost effective and environmentally benign catalysts for electrochemical energy applications.