Assessment of Cheddar Cheese Quality by Chromatographic Analysis of Free Amino Acids and Biogenic Amines

The free amino acids and biogenic amines extracted from normal and late-gassing Cheddar cheeses were derivatized with heptafluorobutyric anhydride and trifluoroacetic anhydride, respectively, before quantification by gas-liquid chromatography. On a microgram scale, twenty amino acids were positively identified in both types of cheese, but only high levels of γ-amino acid butyrate (0.3 to 19.4 mg/g) and small quantities of arginate were found to be associated with “poorly aged” Cheddar cheeses. Histamine (1.54 and 1.22 mg/g) and tyramine (0.32 and 0.43 mg/g) were the bioamines present in highest concentrations in both cheeses.     

深层搅拌水泥土基底加固层的三维随机有限元分析

在软土基坑开挖过程中,围护结构的最大侧向位移往往出现在开挖面以下。常用的防范方法是采用深层搅拌法对设计深度以下2~3 m的软土层进行水泥加固处理,形成水泥土加固层以减少围护结构的侧向位移。由于水泥土的强度具有显著的空间变异性,工程设计中通常采用较为保守的整体强度设计值。考虑深层搅拌桩形成过程中的两种主要不确定性因素:桩身位置不确定性和桩身内部水泥土强度不均匀性,将水泥土加固层的强度模拟为随机场,且将其作为材料变量结合有限元仿真模拟进行受力分析。分析结果表明水泥土加固层的设计强度可表示为钻心取样强度平均值减去t倍标准差,对系数t进行了详细探讨,所得结果可为今后类似工程设计提供参考依据。     

关于住居能源碳排放量影响因素的研究——基于中国省际面板数据的实证分析

以中国省级行政单位为研究对象对与居民生活息息相关的住居领域内所产生的能源消费与CO2排放的地区间差异性进行研究,并在此基础上对产生这一差异性的影响因素进行了深入的分析。以人均碳排放量为因变量,分别从人口、社会和经济特征及区域环境特征两大方面出发选取了10个影响因素作为自变量构建了从2002—2011年10年间以全国28个省份为对象的4个均衡面板数据模型并进行了估计分析。从模型估计结果来看,个人属性以及家庭结构等都对住居领域的碳排放有着显著性的影响;城镇居民的人均住宅建筑面积越大其碳排放量就越高。基于此,研究认为在制定有关节能减排措施时,要充分考虑到个人属性、家庭结构等人口和社会经济性因素以及住宅类型、城市形态等区域环境因素所带来的影响,根据各个地区不同的经济发展水平和实际情况因地制宜地制定和实施节能减排政策。     

AFFS技术在大尺寸LCD-TV的进展（英文）

最近我们发展了AFFS技术,做出了32″LED背光源的LCD-TV,色域达到了105%,对比度1200：1,在140°所有视角的对比度达到了100以上,我们采用双轴补偿膜大大提高了颜色漂移的特性。这些光学特性结果的取得是与工艺制作、光学材料的优化、新AFFS像素的设计分不开的。     

Near-Infrared Reflectance Spectroscopy for Rapid Analysis of Curds during Cheddar Cheese Making

Near-infrared reflectance spectroscopy (NIRS) equations were developed for rapid analysis of curds during Cheddar cheese making. The coefficients of determination (R²) for NIRS and chemical analysis were: moisture (0.982), protein (0.965), fat (0.951), and lactose (0.909). When validation samples were compared by NIRS and chemical analysis, the R²s were moisture (0.984), protein (0.964), fat (0.957), and lactose (0.982). These results suggest that NIRS is applicable for rapidly monitoring chemical changes in curds.     

Mechanism of Release of Nucleotidic Material by Fermenting Brewer's Yeast

SUMMARY— When a strain of brewer's yeast grown under suitable conditions was suspended in a solution of fermentable sugar, nucleotides and other U.V.–absorbing materials were rapidly released from the cells. The extent of release was dependent on the pH of the medium, the temperature, the concentration of fermentable sugar and on the presence of membrane–protecting (Ca⁺⁺ or Mg⁺⁺) or membrane–damaging (butanol, detergent) reagents. The released material was of low molecular weight and appeared to originate in a free intracellular pool. It was concluded that the mechanism of release of nucleotidic material was the result of a change in permeability of the cytoplasmic membrane of yeast contingent upon the transport and metabolism of fermentable sugar. Leakage of nucleotidic material from yeast was considered to be a normal physiological process of consequence in the brewing and wine–making industries.     

Linear Programming and Response Surface Methodology to Optimize Surimi Gel Texture

A formulation optimization study was conducted on surimi gels prepared with starch, and/or raw egg white employing the stepwise method (SM), linear programming (LP), and response surface methodology (RSM). At 78% moisture, the greatest gel strengthening and reduction of expressible moisture occurred at 8% starch, 6% egg white, or a combination of 5% starch and 5% egg white for SM, 5.33% starch and 4.33% egg white for LP, and 3.5% starch and 5% egg white for RSM. RSM resulted in gels with the greatest strength (compressive and penetration forces), followed by LP and SM. The RSM enabled more accurate prediction of textural behavior of final product at various ingredient combinations than the SM or LP.     

Gelatinization and Liquefaction of Starch with a Heat Stable α-Amylase

Sweet potato and corn starches were gelatinized and liquefied to dextrose equivalent (DE) 10 in a steam-jacketed kettle or in a twin-screw extrusion cooker in a single step process with a heat stable ex-amylase. The time required to gelatinize and liquefy 20% starch slurries in a kettle at 95°C was 45 to 50 sec. Starch powder (10 kg/hr) and water (2-6 kg/hr) were fed to an extrusion cooker to adjust the moisture contents of the starch from 20 to 55% (wet basis) and gelatinized and liquefied to DE 10 at a barrel temperature of 120°C or above with 2 to 3% (w/w) a-amylase added. The optimum conditions for the operation were to feed starch with water to maintain 50% moisture and 2% heat stable a-amylase at a barrel temperature of 120°C.     

Isolation and Identification of Volatile Compounds from Roasted Peanuts

Volatile flavor compounds were isolated from 70 kg of freshly roasted Florida Runner peanuts by a specially designed apparatus. The isolated volatile flavor compounds were subjected to extensive gas chromatographic fractionation and the pure fractions obtained were identified by infrared and mass spectrometry. A total of 131 compounds was identified. The following compounds are reported for the first time as flavor components of roasted peanuts: five lactones, incluing γ-crotolactone, 3-methyl-γ-crotolactone and 5-hydroxy-4-nonenoic acid, lactone; four pyrazines, three pyrroles; three pyridines, 13 sulfides, including three monosulfides, six disulfides and four trisulfides; seven thiazoles, two thiophenes, five furanoids, including 2-methyL3(2H)furanone; five oxazoles, three oxazolines, including 2-methyl-3-oxazoline; 12 hydrocarbons, one alcohol, one ketone, two acids, two esters, 2-acetoxy-2-butene, and maltol.     

液压挤压对复合铸造Al3003/Al4004包覆材料显微组织的影响(英文)

研究液压对混合复合铸造Al 3003/Al 4004包覆材料微观组织变化的影响。复合铸造Al 3003/Al 4004包覆材料试样为圆形,由Al 3003(外部)和Al 4004(内部)材料组成。采用液压设备,在温度423 K、挤压比5的条件下制造试样。在挤压之前,Al 4004材料的直径为80 mm,Al 3003材料的厚度为35 mm,在挤压后,2种材料的直径和厚度分别为30 mm和5 mm。研究了2个试样的微观组织和硬度。在挤压之前,复合铸造Al 3003/Al 4004包覆材料横截面的硬度以抛物线的形式向中心增大。然而,在挤压后,Al 4004材料的硬度几乎没有变化。在挤压之前,Al 3003和Al 4004材料的界面存在大量直径超过1 mm的大空洞,这些大空洞随着液压过程的进行而消失。