Use of cold microfiltration retentates produced with polymeric membranes for standardization of milks for manufacture of pizza cheese

Pizza cheese was manufactured with milk (12.1% total solids, 3.1% casein, 3.1% fat) standardized with microfiltered (MF) and diafiltered retentates. Polymeric, spiral-wound MF membranes were used to process cold (<7°C) skim milk, and diafiltration of MF retentates resulted in at least 36% removal of serum protein on a true protein basis. Cheese milks were obtained by blending the MF retentate (16.4% total solids, 11.0% casein, 0.4% fat) with whole milk (12.1% total solids, 2.4% casein, 3.4% fat). Control cheese was made with part-skim milk (10.9% total solids, 2.4% casein, 2.4% fat). Initial trials with MF standardized milk resulted in cheese with approximately 2 to 3% lower moisture (45%) than control cheese (∼47 to 48%). Cheese-making procedures (cutting conditions) were then altered to obtain a similar moisture content in all cheeses by using a lower setting temperature, increasing the curd size, and lowering the wash water temperature during manufacture of the MF cheeses. Two types of MF standardized cheeses were produced, one with preacidification of milk to pH 6.4 (pH6.4MF) and another made from milk preacidified to pH 6.3 (pH6.3MF). Cheese functionality was assessed by dynamic low-amplitude oscillatory rheology, University of Wisconsin MeltProfiler, and performance on pizza. Nitrogen recoveries were significantly higher in MF standardized cheeses. Fat recoveries were higher in the pH6.3MF cheese than the control or pH6.4MF cheese. Moisture-adjusted cheese yield was significantly higher in the 2 MF-fortified cheeses compared with the control cheese. Maximum loss tangent (LT_max) values were not significantly different among the 3 cheeses, suggesting that these cheeses had similar meltability. The LT_max values increased during ripening. The temperature at which the LT_max was observed was highest in control cheese and was lower in the pH6.3MF cheese than in the pH6.4MF cheese. The temperature of the LT_max decreased with age for all 3 cheeses. Values of 12% trichloroacetic acid soluble nitrogen levels were similar in all cheeses. Performance on pizza was similar for all cheeses. The use of MF retentates derived with polymeric membranes was successful in increasing cheese yield, and cheese quality was similar in the control and MF standardized cheeses.     

填絮纤维新技术的开发

做填絮纤维的最常用的高聚物是PET,其特性主要取决于纤维的线密度、空间构型、特殊的填絮纤维油剂、纤维表面性能和纤维蓬松性(即回弹性)。基本技术关键是油剂的研制,提供柔软性(无滑动粘附性)、平滑性(低摩擦系数)与合乎要求的触感。这些性能与一系列支撑性能一起,导致填絮纤维市场的发展。     

儿童排铅食品问题的研究

列举了铅的毒性和作用机制，尤其是对儿童健康的影响，并对排铅的功能性成分进行了论述，提出研制生产儿童排铅食品势在必行。     

Carbon materials modified by plasma treatment as electrodes for supercapacitors

The carbon material was modified by RF plasma with various reactive gases: O₂, Ar and CO₂. Physicochemical properties of the final carbon products were characterized using different techniques such as gas adsorption method and XPS. Plasma modified materials enriched in oxygen functionalities were investigated as electrodes for supercapacitors in acidic medium. The electrochemical measurements have been carried out using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The electrochemical measurements have confirmed that capacity characteristics are closely connected with a type of plasma exposition. Modification processes have an influence on the kind and amount of surface functional groups in the carbon matrix. The moderate increase of capacity of carbon materials modified by plasma has been observed using symmetric two-electrode systems. Whereas investigations made in three-electrode system proved that the suitable selection of plasma modification parameters allows to obtain promising negative and positive electrode materials for supercapacitor application.     

海量存储系统评测体系的研究

随着信息化建设的逐步深入,对计算机系统的两大能力,即运算和存储能力的要求越来越高,尤其是存储能力.主要研究了基于SAN存储网络的海量存储系统的评测体系.评测体系主要从性能、能耗、功能、可用性、可靠性5个方面,典型应用、存储系统软件、信息组织核心系统、存储网络、存储设备、存储器件6个层次构建.从每个角度都提出了具体的指标...     

紫薯茎叶中黄酮的提取及其功能性研究进展

黄酮类化合物广泛存在于植物界,是许多中草药的有效成分。在自然界中最常见的是黄酮和黄酮醇,此外,还有双氢黄醇、异黄酮、双黄酮、黄烷醇、查尔酮、橙酮及花色苷等。由于类黄酮具有很强的抗氧化和消除自由基的作用,备受国内外研究者的青睐,成为研究的热点。黄酮类化合物有着重要的医用价值,主要体现在:抗炎症、抗过敏;抑制细菌、抑制病毒;防治肝病、防治血管疾病;抗肿瘤、抗化学毒物等。本文从节约资源、提高黄酮得率、实验操作性强等方面分析,选取紫薯茎叶为实验材料,并结合国内外大量研究理论成果,论述了黄酮类化合物的提取方法,将这些方法的优缺点进行了总结,同时,详细的阐述了黄酮类化合物的功能性研究进展,希望对黄酮的研究者起到借鉴、提供参考的价值。     

发酵肉制品功能性发酵剂研究现状

功能性发酵剂具备产良好风味、促进安全或益生性等优势,在弥补工业化、健康化发酵肉制品风味缺陷上具有巨大潜力,且对致病菌、生物胺等潜在安全风险的控制具有重要作用,甚至还可给产品带来益生特性。本文着重从风味、安全性、益生性角度对功能性发酵剂研究现状进行分类概述,并对其未来研究方向进行展望。     

Microstructural characterization of aromatic copolyesters made by step reactions,by gradient polymer elution chromatography

The potentials of Gradient Polymer Elution Chromatography (GPEC) in both the Reversed‐Phase (RP) and Normal‐Phase (NP) mode, for the characterization of aromatic copolyesters made by step reactions, according to their chemical microstructure, were studied. Hereto, a number of copolyesters, varying in molar mass and chemical composition (CC) were synthesized, which allowed a systematic study on the effects of those parameters in GPEC. By RP‐GPEC, highly detailed separations were obtained. Information on chemical composition differences could, however, only be obtained for the lower molar masses. From these results, qualitative evidence for differences in the chemical microstructure of two strongly resembling copolyesters was found that could not be obtained by other methods such as SEC and NMR. Nevertheless, it was found difficult to unambiguously assign observed differences in the high molar mass parts of RP‐GPEC chromatograms. Therefore, RP‐GPEC must mainly be considered as a versatile, qualitative fingerprinting tool. In contrast, NP‐GPEC provides more and quantitative information on microstructural differences. By a combination of SEC and NP‐GPEC the Molar‐Mass‐Functionality‐Type‐Distribution (MMFTD) of the (co)polyesters, and the Molar‐Mass‐Chemical‐Composition‐Distribution (MMCCD) of the fraction containing two alcoholic end groups of the copolyesters could be studied. Significant differences between strongly resembling copolyesters were found which, for the MMCCDs, can only be the cause of the relative importance of reaction kinetics in step reaction copolymers. This makes the assumption that a predictable, theoretical statistically determined CCD is formed in all cases, questionable. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 183–201, 1999