用升华与蒸发联合法干燥食品的物理性质

Drying is an important unit operation in processing of biological resources. The drying process may influence the product properties and quality, which may shrink, break or undergo rheological, physical and biochemical changes. The important parameters responsible for such changes are drying conditions, type of drying technology and residence drying time. Thermal conductivity, thermal-mass diffusivity, enthalpy, porosity and density are the main material property and heat-mass transfer parameters, which are essential for understanding the changes in product quality and for designing and dimensioning the drying processes. In this paper physical properties of food products undergoing a combined sublimation and evaporation were studied. Pieces of vegetables and potatoes were dried in a heat pump fluidized bed dryer at combined modes with temperatures below the freezing point in the beginning and a final drying step at temperatures above the freezing point. Samples of products were tested at different moisture contents with respect to physical properties. Physical properties of leek and potato samples were measured and mass diffusivities were determined from drying kinetic data. Based on bulk density and rehydration measurements it was clearly observed that drying temperature and modes influenced the final product physical properties. The potato cuberun dried with initial atmospheric freeze-drying step had rehydration ability 430% above a run dried only above the freezing point. The average effective mass diffusivity for 5 mm slabs of leek was 0.5×10^-11m^2·s^-1 for the sublimation stage and 2.2×10^-11m^2·s^-1 for the evaooration stage.     

白炭黑的理化性质对橡胶制品性能及加工工艺影响的研究

研究了白炭黑的理化性质-表面组织、pH值、比表面积、吸附等对橡胶制品性能及加工工艺的影响.     

On The Drying of Food Products in a Tunnel Dryer

ABSTRACT

We present a dryer model for simulating the drying of hygroscopic-porous food products in a tunnel dryer. The model employs an improved receding-front formulation by taking into consideration the material volumetric shrinkage and the variation of the heat and mass transfer coefficient during drying. Predicted results show close agreement when compared with experimental data. We report a parametric analysis using the dryer model to study the drying transient and the need to cascade the drying process so as to maximise the drying potential of the air stream.     

育苗基质物理及化学性质的综述

从基质的粒径大小、容重、密度、孔隙度、保水性等方面总结阐述了基质物理性质方面的研究指标及研究进展;从有效成分,酸碱度、电导率、离子吸附与交换能力、盐基交换量、缓冲能力等方面阐述了基质的化学性质方面的研究指标及研究进展。且指出,利用农业废料开发新型基质,填补国内空缺,是未来我国基质开发研究的一个很重要的方向。     

食品和农产品干燥的一种有效方法-红外加热法

农业和食品行业需要能源高效和环境友好的干燥技术,最近红外加热干燥的应用得到广泛研究。作为现代干燥技术的另一种选择,红外干燥具有加热均匀、干燥速率高、干燥时间短、节约能源、产品品质和安全性高等引人注目的优点。研究表明。将红外方法可以减少干燥时间并且节能。与热可以对果蔬实现同步漂烫和干燥,干燥和热风干燥相结合能够有效的减少干燥时间。所开发的红外冷冻相继干燥常规的空气干燥或冷冻干燥相比,更适合于生产高品质的酥脆果蔬片。红外加对稻谷进行同步干燥和杀虫。本文将综述红外加热技术的最新研究和进展。     

食品类专业物理化学课堂活化的教学探索

物理化学是食品类专业的基础课,课时有限且教学难度大,本文介绍了使物理化学课堂教学活泼化的方法和体会。通过提高教师的食品专业知识、针对专业特点优化教学内容,穿插人文化学史教育,设计新实验,传统板书与多媒体技术结合等手段,激发学生的学习兴趣,形成农林院校食品专业物理化学课程教学新模式。     

食品专业物理化学教学改革的探索

根据食品专业的培养目标,对物理化学课程实施了以教学内容、教学方法、教学手段以及考核方式为主的教学改革,利定了符合专业实际的知识体系,增强了课程教学的实用性,调动了学生学习的积极性,取得了明显的教学效果。     

A Study of Coupled Heat and Mass Transfer in Composite Food Products during Convective Drying

A two-dimensional liquid diffusion model was developed to predict the variation of transient moisture content and temperature distribution within model composite food products. Rectangular-shaped potato and apple slices were used to form the model composite samples for experimental tests. To verify the predictions of the theoretical model, a series of experiments were conducted on the model composite samples using a heat pump-assisted convective dryer. Effects of using different adhesives to hold the two slices forming the composite products, flipping of the products at selected intervals of time and variation of individual slice thickness were investigated both experimentally and numerically. Predictions of the numerical model are in good agreement with the experimental results.     

Physical and Morphological Properties of Combined Treated Wood Polymer Composites by Maleic Anhydride and Methyl Methacrylate

Wood polymer composites were prepared by consecutive impregnation with maleic anhydride (MAN) and methyl methacrylate (MMA). Samples impregnated with MAN alone, were heated at 120°C and 150°C for 4 and 8 h. Based on the Fourier transform infrared (FT-IR) analysis and soaking-drying test results, treatment with MAN at 150°C for 4 h resulted in formation of stable crosslinks. In the second stage, MMA was used for in situ polymerization within MAN-treated wood. Field emission scanning electron microscopy observation and FT-IR analysis indicated that MMA copolymerized with MAN, and the resultant polymer filled up the lumen and is also grafted on to the cell wall. Improvement of water repellency and dimensional stability were observed in the treated samples, particularly in combined treated samples. The MAN/MMA treatment improved interaction between polymer and wood.     

《材料物理性能》课程建设探索与实践

<材料物理性能>是材料科学与工程专业本科学生的一门骨干专业基础课,学生对该课程掌握程度如何,直接影响后续课程的学习.文章从拓宽专业口径,培养创新型人才为出发点,在课程内容的优化、教学方法和手段的改进、创新能力的培养等方面进行了积极的探索.     

尼莫地平注射乳剂制备方法与物理性质的测定

用国产原料制备尼莫地平注射乳剂,并且对其物理性质进行测定,结果表明其符合注射要求,主要参数有粒度分度、pH值、渗透压等.     

Recent Studies of Physical Properties of Highly Oriented Polyethylene

Recent studies of the structure and properties of ultra high modulus polyethylenes are presented. The physical properties received include dynamic mechanical behaviour, creep, shrinkage, shrinkage force, melting behaviour, thermal expansion and barrier properties.     

离子液体物理化学性质数据库及QSPR分析

收集了1984~2004年文献中报道的有关离子液体物理性质的数据,建立了离子液体物理性质数据库. 数据库共包含600多种离子液体,约3500条数据. 基于这些数据,进行了离子液体定量结构-性质相关性(QSPR)的研究,对两种常见体系(双取代咪唑四氟硼酸盐和双取代咪唑六氟磷酸盐)的熔点进行了关联和预测. 研究结果对离子液体的设计与应用具有指导意义.     

Influence of Atmospheric Sublimation and Evaporation on the Heat Pump Fluid Bed Drying of Bovine Intestines

Experiments on atmospheric two-stage fluidized bed drying of bovine intestines with heat pump were carried out. The investigation covers innovative fluidized bed heat pump drying of bovine intestines. The two-stage drying consists of atmospheric moisture sublimation immediately followed by evaporation. Studies were done to establish the influence of the drying condition on the drying characteristics and product quality of bovine intestines and properties focusing on kinetics, diffusion, and color. The investigation of the drying characteristics has been conducted during moisture removal by evaporation and combined sublimation and evaporation. The effect of drying temperature on the drying constants was determined by fitting the experimental data using regression analysis techniques. The investigation revealed that the drying kinetics is most significantly affected by temperature. Correlations expressing the drying constants and effective moisture diffusivity dependence on the drying conditions are reported.     

A Study into the Influence of Paper Coatings on Paper Properties and Print Quality of Dye Sublimation Thermal Prints

The need for good quality paper for dye sublimation transfer printing has been reported previously as a principal requirement for the process. Pigmented coated papers have gained acceptance in the traditional paper printing industry, but, despite their importance, have inspired very few reports in literature about their application in heat transfer printing.

In the current work, we studied the influence of both clay and ground calcium carbonate (GCC) pigments and the incorporation of plastic pigment on the surface structure and mechanical properties of the coated paper used for transfer printing. The results showed that paper coating significantly reduced the surface roughness of the paper. The mechanical properties of the prepared coated paper, including tensile strength, stretch, tensile energy absorption (TEA), and burst index, were improved when coated compared to those of uncoated paper. The addition of plastic pigment to the coating mixture helped improve the paper's properties.

The optical density of the transfer-printed polyester fabric using the prepared coated paper was also compared with that of uncoated paper. It was shown that a slight increase in optical density was evident in the coated paper.

The possibility of producing a second polyester print from the exhaust paper was also investigated. Coated paper incorporating plastic pigment, in particular, showed higher optical density than did uncoated paper.

We found that coated paper based on clay, GCC, clay/plastic pigment, or GCC/plastic pigment consumed less dye paste than uncoated paper though producing printed fabric with higher optical density—especially in the second print.     

Physical Properties and Structure of Silica-Alumina-Europium Oxide Glasses

SiO₂–Al₂O3–Eu₂O₃ glasses were prepared for the composition 50siO₂·(50 – x )Al₂O_3·xEu₂O₃, and their density, sound velocity, and elastic modulus were measured. The chemical shift of the AIK a band emission spectra and the isomer shift of ¹⁵¹Eu by Mössbauer effect were obtained to determine the coordination states of Al³⁺ and Eu³⁺ ions in these glasses. It was found that the coordination number of Eu³⁺ ions was 12 and that the average coordination number of A1³⁺ ions was almost 5 in these glasses. By introducing Eu₂O₃, the packing of constituent ions was strongly enhanced and the elastic modulus increased in this system. The compositional dependence of the molar volume and elastic modulus were explained by these states of high coordination number for Eu³⁺ and low coordination number for Al³⁺ ions compared with those in the corresponding M₂O₃ crystals.     

Influence of Combined Hot Air Impingement and Infrared Drying on Drying Kinetics and Physical Properties of Potato Chips

Air jet impingement combined with infrared drying (IMIRD) was developed as an alternative processing method to produce health-friendly potato chips in place of conventional deep-fat frying. This article investigates the effects of IMIRD compared to air jet impingement drying alone (IMD) and conventional convective drying (CCVD) on potato being processed as potato chips in term of drying characteristics, quality attributes (shrinkage, color, and hardness), and specific energy consumption (SEC) of the dryer. The experiments were carried out at three different air velocities (5, 10, 15 m/s) and infrared intensities (0.16, 0.27, and 0.33 W/cm²) at a fixed air temperature of 85°C. The experimental results show that the drying air velocity and infrared intensity had a significant effect on the moisture removal from potato slices. IMIRD, compared to IMD and CCVD, provided a higher drying rate, less shrinkage, lower hardness, and less color deterioration. An increase in air velocity at each infrared intensity caused a decrease in the total SEC value.     

无机玻璃物理性质计算的自动化及其实现方法

无机玻璃物理性质计算的自动化及其实现方法王泽斌（中国兵器工业总公司国营第五一零八厂４４１４０６）ＡｕｔｏｍａｔｉｚａｔｉｏｎｏｆＣａｌｃｕｌａｔｉｎｇＰｈｙｓｉｃａｌＰｒｏｐｅｒｔｉｅｓｏｆＩｎｏｒｇａｎｉｃＧｌａｓｓｅｓａｎｄＩｔｓＩｍｐｌｅｍｅｎ...     

Effects of Drying Schedules on Physical and Mechanical Properties in Paulownia Wood

The effects of six drying schedules on physical and mechanical properties of Paulownia wood (Paulownia fortune Seem.) were studied. Three schedules were based on the recommendations by Forest Product Laboratory (FPL), while the other three were established based on diffusion theory. FPL schedules consisted of a mild (T₆E₃), a moderate (T₆E₄), and a severe (T₇E₄) drying schedule; diffusion schedules consisted of three initial moisture contents (MC) of 113% (Dif-1), 75.5% (Dif-2), and 53.5% (Dif-3). Boards with a commercial thickness of 5 cm were randomly dried to the final moisture content of 8 ± 2% in all six schedules. Results indicated that drying under diffusion schedules had the most improved properties due to the beneficial effect of heat upon wood plasticity. However, lower plasticity effect in FPL schedules, due to lower temperatures, resulted in lower properties in most cases.     

海产品及水发食品中甲醛快速检测方法研究进展

甲醛是致癌、致畸物质,世界各国均严禁将甲醛及其化合物用作食品添加剂,食品中的甲醛问题成为世界公共卫生系统关注的焦点,研究食品中甲醛的快速检测方法对保障消费者的健康以及维护公共卫生安全具有重要意义,本文对海产品及水发食品中甲醛的快速检测分析方法研究进展进行综述,以期对同行开展相关研究有所帮助。