THERMAL INACTIVATION OF PEA FLOUR LIPOXYGENASE

Lipoxygenase (LOX) was determined in pea flour (9.6% moisture) samples which had been exposed to 90–130°C for 5–45 min, and in crude aqueous extracts (5%; pH 6.7) of previously unheated pea flour which had been exposed to 40–80°C for 5–30 min. The rate of thermal inactivation of pea LOX was shown to follow first-order reaction kinetics. The rate constants, k(min^?1), ranged from 0.005 to 0.252 for the flour, and from 0.068 to 0.267 (60–80°C) for the crude extract. The respective thermodynamic values were: for the energy of activation (E_a), 126.2 and 64.6 kJmole^?1; for the enthalpy of activation (ΔH^?), 123.1 and 61.8 kJmole^?1; for the free energy of activation (Δ^?), 118.0 and 101.4 kJmole^?1. The greater thermostability of LOX in the pea flour under dry-heat conditions, and the observed differences in the E_a, ΔH^? and ΔS^? values, may be accounted for by its possible complexation with other macromolecules and by the structure of the water surrounding the native enzyme.     

Viscosity of Molten Milk Chocolate with Lactose from Spray-Dried Whole-Milk Powders

Dry whole-milk powders containing 0, 30, 50 and 70% nominal lactose prepared by spray-drying alone, or followed by post-drying crystallization, were incorporated into milk chocolate to give 0–50% substitution of lactose for sucrose. Increasing the concentration of amorphous lactose from spray-dried powders in the chocolates decreased viscosity, increased particle size of refined chocolate mass, and lowered the concentration of surface-active agents at which a minimum in Casson yield value was observed. Increasing the concentration of crystalline lactose from milk powders in the chocolates increased viscosity, decreased particle size, and increased the concentration of surface-active agents at which a minimum in Casson yield value was observed. Conditions which affect lactose crystallinity in milk powders, such as improper storage and handling prior to use in chocolate production, could be responsible for variations in chocolate viscosity noted sometimes by processors.     

Computer Simulations of R-Curve Behavior in Microcracking Materials

A computer program has been developed which simulates the process of microcracking in two-phase ceramic materials. This simulation provides a method of examining the complex interactions which occur between a propagating crack and the residually stressed particles around it. As the residual stresses near second-phase inclusions are relieved by microcrack formation, a process zone forms around the main crack, partially shielding it. The resulting crack resistance curves, or R curves, associated with crack shielding mechanisms are generated by the program. Three variables— the microcrack density (f_s), the dilatant strain associated with each microcracked particle (θ), and the orientation of the microcracks (Ψ)— were used to determine their influence on fracture toughness. The steady-state toughness was found to increase with second-phase particle additions, increased dilatant strain, and the formation of microcracks parallel to the direction of applied stress. However, the magnitude of toughening increase attained in these-simulations was generally lower than that predicted by continuum models. This discrepancy is attributed to the fact that interactions between microcracks produce frontal zones which result in a positive Δk , and hence, a lower steady-state toughness. This behavior is enhanced when microcracks link with the main crack to promote further extension.     

THE FUTURE CENTRAL CITY: GENTRIFIED OR ABANDONED?*

Displacement of minorities and low income individuals has been reported in the popular press and in a number of scholarly case studies. Whether displacement is a major national problem or limited to a number of isolated neighborhoods is the subject of national debate. Urban scholars point to decreasing overall demand for central city properties and an overall decrease in the number of white individuals living in the central city to discount the significance of the reports of displacement. This article analyzes both migration by race and housing trends in central cities. The analysis proceeds from nationally aggregated data to central city level and census tract level data. The argument is made that while the population is decreasing in central cities, the number of middle class individuals is increasing in many central city neighborhoods and the number of available housing units is decreasing. This is increasing the competition for existing units. If these trends continue and overall housing costs continue to increase, displacement is likely to become widespread.     

挖掘采购的战略潜力

要想发挥采购的商业潜质,必须将采购的功能从提供支持转变为创造价值.希望通过采购提升业绩的公司高管应该思考提高采购效率所需的流程、技术和员工培养机制.埃森哲的调研结果可以为你所用.     

Sorption of Ethyl Butyrate and Octanal Constituents of Orange Essence by Polymeric Adsorbents

Sorption characteristics, rates and capacities of polymeric adsorbents (XAD-4, XAD-7, XAD-16, Duolite ES-865, Duolite S-761, Porapak-Q and XUS-43436) for ethyl butyrate and octanal were determined using model solutions. Sorption of these two principal components of aqueous orange essence, was evaluated utilizing the Freundlich isotherm model. Breakthrough curves were determined using XAD-16 as adsorbent. The capacity of XAD-16 for ethyl butyrate in the column system was 426±212 mg/g. There was no column breakthrough for octanal even after 130 bed volumes. Most (91.4%) of the adsorbed ethyl butyrate was eluted from XAD-16 resin by 95% ethanol elution. Recovery of adsorbed octanal from the resin was 66.4%.     

Effect of Gamma Irradiation on the Carotene Content of Mangos and Red Capsicums

Gamma irradiation of red capsicums (cv. Five Star) at 75 and 300 Gy had no significant effects on the carotene level of unstored red capsicums or red capsicums stored at 5°C for 3 wk. Gamma irradiation of mangos (cv. Kensington Pride) at 75, 300 and 600 Gy had no significant effects on the carotene content. Altering the conditions of irradiation (lower temperature, nitrogen atmosphere, lower dose rate) resulted in slightly higher carotene levels than those associated with irradiation under normal ambient conditions.     

Oxycarbide Glasses in the Mg-Al-Si-O-C System

Oxycarbide glasses in the Mg-Al-Si-O-C system were produced at initial carbon levels of 0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 wt%. Carbon was incorporated into the glass melts by means of SiC additions. The glasses were melted between 1750° and 1800°C under nitrogen atmospheres. The limit of carbon incorporation was reached at the 2.5% carbon level, as these glasses crystallized (predominantly cordierite, 2MgO˙2Al₂O₃˙5SiO₂) upon gradual cooling from the meit. Glasses containing less than 2.5% carbon were amorphous according to standard X-ray diffraction methods. Further examination of these oxycarbide glasses by transmission electron microscopy indicated the lack of microcrystalline phases and the potential for producing clear inclusion-free glasses. The Mg-Al-Si-O-C glasses showed significant increases in density, Young's elastic modulus, shear modulus, Vickers hardness, and fracture toughness with increasing carbon content.