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。     

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.     

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.     

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C6F12O with a low global warming potential

Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a negative effect on the global environment owing to its high global warming potential (GWP) value. An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF₃ with C₆F₁₂O, which has a low GWP and is in a liquid state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using inductively coupled CF₄ +C₆F₁₂O+O₂ mixed plasmas. Subsequently, the etching characteristics of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated. A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface. Consequently, the etching characteristics of the C₆F₁₂O mixed plasma exhibited a lower etching rate, higher SiON/Si selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF₃ mixed plasma. In addition, the C₆F₁₂O gas can be recovered in the liquid state, thereby decreasing global warming. These results confirmed that the C₆F₁₂O precursor can sufficiently replace the conventional etching gas.