Lactosylation of milk proteins during the manufacture and storage of skim milk powders

Extensive lactosylation of milk proteins in standard skim milk powder dried against air between 185 and 90°C (inlet and outlet temperatures of the air) was detected by capillary electrophoresis. Optimisation of the drying conditions included keeping the outlet temperature low (preferably <80°C), since this was the parameter which most affected the extent of lactosylation of milk proteins. The inlet temperature was set in order to obtain the best compromise between a low extent of lactosylation and a high drying rate (170–175°C). These conditions allowed the manufacture of low-lactosylated skim milk powder. Storage of freeze-dried and control low-lactosylated skim milk powder at different temperatures showed that both temperature and moisture content affected the progress of lactosylation during storage. Further drying to less than 2.5% moisture content (w/w) and storage at low temperatures were required to prevent the development of lactosylation in the low-lactosylated skim milk powder.     

Minimizing Induction Motor Losses by Excitation Control in Variable Frequency Drives

For a given induction motor under a specified load condition, a combination of stator voltage and frequency exists which results in minimum power losses. This optimal operating point is calculated over the complete speed and torque range using a model of the induction machine including saturation, stray losses, and skin effect. It is shown that substantial power savings can be achieved compared to conventional programmed volts/hertz control and that main flux saturation has a dominant role in determining the optimal operating condition. A detailed analysis of the mechanisms yielding power savings is presented as well as an experimental confirmation of the theoretical results. These results are utilized to study thetinfluence of machine size, rated slip, and other factors on the optimal performance.     

Preparation and Study of Pd Catalysts Supported on Activated Carbon Cloth (ACC) for Direct Synthesis of H2O2 from H2 and O2

Activated carbon cloths (ACCs) were used as supports for Pd catalysts. The catalyst preparation was carried out by the impregnation method using acidic solution of palladium dichloride (PdCl₂) as metal precursor. The effects of the oxidation state of the loaded metal, heat treatment of the catalysts in different atmosphere (H₂, air) at different temperatures and surface chemistry of the support on the catalyst characterizations and the catalytic activities were investigated. Wet oxidation of ACC was done by nitric acid in order to induce oxygen-containing surface functional groups. Surface chemistry of the support and oxidation state of the metallic phase was investigated by means of XPS, TPD, SEM, DTA and TGA tests. Direct synthesis of hydrogen peroxide from H₂ and O₂ was performed batch wise in a stainless steel autoclave. The reactions were conducted under high pressure (38 bar) at 0 °C and methanol was used as reaction medium. The direct synthesis results showed that the oxygen-containing surface functional groups increase the selectivity of the catalysts by reducing the rate of water production. Existence of the oxidized state of Pd (PdO) also makes the catalyst more selective than the corresponding zerovalent state (Pd0). PdO affected on selectivity by increasing the rate of H₂O₂ production and reducing the amount of production of water, simultaneously.     

A Kleene Theorem for a Class of Planar Acyclic Graphs

In this paper, we study planar directed ordered connected acyclic graphs, in particular graphs that can be built over a (finite) doubly ranked alphabet by parallel and serial composition. On the one hand we introduce finite automata on graphs and, on the other hand, rational expressions that involve union, nondeterministic parallel composition, serial composition, and the iterations of these compositions. We prove a Kleene Theorem linking these two characterizations of sets of graphs.     

消费类应用市场概览

市场概述消费类市场应用范围宽广,而且由于有创新产品如平板电脑等的推出,其应用范围还在不断演变。由于难以论及所有消费应用,本文将重点探讨传统"家庭娱乐"类消费应用,如电视、机顶盒(STB)及数字视频播放机(如DVD、DVR等,简称DVx)。过去几年来,这些应用的变化颇大,功率电子设计工程师需要特别注意。这些应用中变化最大的就是     

Potential use of niosomes for encapsulation of nisin and EDTA and their antibacterial activity enhancement

Different formulations of niosomes were prepared using Span 80 with sodium stearoyl lactate (SSL) and PEG400 as additives. The corresponding niosomes were used for encapsulation of antibacterial agents including nisin and EDTA. Characterization of unloaded and loaded niosomes was carried out by means of size, zeta-potential, and also encapsulation efficiency and antibacterial activity specifically for loaded niosomes. Unloaded niosomes were stable at least 2 months when temperature challenge was applied at 4 °C, RT, and 45 °C. An addition of 0.5 mM SSL, both with and without PEG was found to enhance stability of loaded niosomes throughout 2-months of storage. Effect of niosome formulation to zeta potential and encapsulation efficiency of nisin and EDTA was discussed in this paper. A 96-well plate assay was used to assess the antibacterial activity between free and encapsulated forms of nisin and EDTA against Staphylococcus aureus and Escherichia coli. A higher and longer-lasting inhibition effect of encapsulated nisin and EDTA against S. aureus as compared to their free forms was observed in an encapsulation using niosome formulations S_0.5s and S_1.0s, both with and without PEG. To our knowledge, this work is the first report on applying niosomes for encapsulation of nisin and EDTA. The results in this study offer an alternative approach to encapsulation of nisin as good as or better than liposomes.