Instant infusion pasteurisation of bovine milk. II. Effects on indigenous milk enzymes activity and whey protein denaturation

Direct heat treatment of two milk types, skimmed and nonstandardised full‐fat, was performed by instant steam infusion and compared with indirect heating. Infusion conditions were temperatures of 72–120°C combined with holding times of 100–700 ms, and indirect heat conditions were 72°C/15 s and 85°C/30 s. The activity of indigenous enzymes such as alkaline phosphatase, lactoperoxidase, xanthine oxidase and γ‐glutamyl transpeptidase was evaluated. Infusion temperature was the main determinant of inactivation. Whey protein denaturation represented by β‐lactoglobulin increased significantly with infusion temperature. The nonstandardised milk had a higher denaturation rate than skimmed milk. The effect of instant infusion on pH and milk fat globule size in relation to whey protein denaturation and association is discussed.     

英国国家电网公司在电力系统状态估计器及安全分析方面的经验

本文叙述了由安装在英国国家电网公司新国调中心的新型能量管理系统所提供的实时网络分析的应用，并介绍了第一年的运行经验．对经常出现的某些状态估计问题的解决方法和作者所作的尝试的结论进行了讨论，以对安全估计器的结果与现有的离线研究方法的结果进行比较．文章还对应用实时网络分析时遇到的一些原始缺陷的观察结果和在短时段及较长时段内解决这些问题的方法进行了讨论．     

A Large Deformation Model for the Elastic Moduli of Two-dimensional Cellular Materials

1Introduction Themechanicalbehaviorofcellularmaterialsde pendsontheirrelativedensity,cellgeometryandthema terialpropertiesofthesolidfromwhichtheyaremade.Theelasticmoduliofcellularmaterialscanbederived fromananalysisofthedeformationmechanismofthecell members.Thesimplegeometryofanidealizedunitcell allowsthederivationofrelationsbetweenmicro structural featuresandeffectivemechanicalproperties.Manytheoreticalmodelshavebeendevelopedtopre dicttheelasticmoduliofcellularmaterials[14].AbdEl Sayedetal[…     

ECOLOGICAL RISK-ASSESSMENT METHODOLOGY: A UK CASE STUDY FOR LANDFILLS

The paper presents an ecological risk-assessment methodology which (a) addresses surface-water exposures to aquatic mammals and birds, and (b) accounts for long-term accumulation and biomagnification of pollutants. The methodology has been adapted from those developed in the USA for compliance with US Environmental Protection Agency requirements, and combines predicted or measured surface-water concentration data with information on the natural history of wildlife species and chemical-specific bioaccumulation factors, to determine whether estimated exposures would exceed toxicological criteria. Whilst the methodology is applied to metals in leachate discharges from landfill sites, the general approach is applicable to other industrial sites. The approach could provide the basis for a shift towards more numerical risk-based ecological assessments in a wide variety of contexts.     

The Management of Water Colour in Peatland Catchments

The problems of water-colour management in peatland catchments are discussed. Colour may be managed in three areas of the reservoir catchment system: on the catchment itself, in the channel/conduit system and within the reservoir. Whilst a number of workers have considered the management of catchment areas and some have evolved tributary turnout strategies, no previous research has considered the role of the reservoir in the amelioration or enhancement of water colour. The management of water colour at Thornton Moor catchment (near Bradford) is described. In this catchment a staged approach has been adopted, with colour being managed in an integrated manner at three stages along the catchment/conduit/reservoir system.     

Growth and metabolism of selected strains of probiotic bacteria in milk

Growth and metabolism of five probiotic strains with well-documented health effects were studied in ultra-high temperature (UHT) treated milk, supplemented with 0.5% (w/v) tryptone or 0.75% (w/v) fructose. The probiotic strains were Lactobacillus acidophilus La5, Lb. acidophilus 1748, Lactobacillus rhamnosus GG, Lactobacillus reuteri SD 2112 and Bifidobacterium animalis BB12. Fermentation was followed for 72 h at 37 degrees C and the samples were analysed for pH, log cfu ml(-1), volatile compounds, organic acids and carbon dioxide. The strains reduced pH from 6.7 to between 3.9 and 4.4 after 24 h of incubation. All strains attained viable cell counts above 8.7-9.18 log cfu ml(-1) after 6-16 h of incubation. The two Lb. acidophilus strains showed a stable level of viable cells during 12-72 h of incubation but the three other strains showed a reduction of 0.4-1.1 log cfu ml(-1) from 24 to 72 h of incubation. However, all strains showed cell levels between 7.8 and 8.7 log cfu ml(-1) after 72 h of incubation. After 48 h of incubation, the amount of lactic acid produced varied according to strain from 6949 to 14,000 mg kg(-1) and acetic acid produced varied from 0 to 6901 mg kg(-1). Three of the strains metabolised citrate but only low amounts of diacetyl and acetoin were detected within strains, 0.2-0.8 and 6.5-10 mg kg(-1), respectively. Carbon dioxide produced varied from 221 to 3942 mg kg(-1) and was connected to the citrate-fermenting ability of the strain used and their carbohydrate fermentation pathway. Three of the strains produced detectable levels of acetaldehyde and the concentration varied from 9.4 to 12.6 mg kg(-1) after 24 h of incubation. All five probiotic strains showed very different profiles of metabolites during fermentation; however, the two Lb. acidophilus strains were the most alike. Our findings show the importance of controlling the fermentation time since the probiotic strains produced different amounts of metabolic products according to fermentation time.