THE EFFECTS OF STORAGE AND HEATING ON LYSINE AVAILABILITY OF FOOD-GRADE PROTEINS FROM PASTURE HERBAGE AS MEASURED BY CHEMICAL, BIOLOGICAL AND MICROBIOLOGICAL ASSAYS

Food-grade protein concentrates isolated from pasture herbage stored and/or heated either alone or with glucose to cause various types of damage to lysine were analyzed for available lysine using chemical procedures and bioassays with chickens, mice, rats and protozoon Tetrahy-mena pyriformis. There were substantial differences in the results obtained with the various chemical methods which showed their different sensitivities to a particular type of lysine damage which had occurred during storage and heat processing. Overall, chemical procedures gave lower values for available lysine than the biological ones, and thus may underestimate availability. The responses of mice and Tetrahymena pyriformis to various types of lysine damage were similar to those observed with chicks, while rats appeared to be less sensitive test animals in detecting the changes in lysine availability in stored or heat processed foods. The necessity to adapt a rapid system for lysine availability determination in foodstuffs and cereal-based diets is discussed with reference to the proper quality control of food-grade proteins, isolated from pasture herbage and subjected to storage or heat processing, before being used in feeding schemes with school children in developing countries. The use of Tetrahymena pyriformis or a simple chemical procedure may provide a built-in safety margin to insure proper quality control of food-grade proteins.     

PARTICULATE MATTER EXPOSURES TO COMMUTERS IN HONG KONG

ABSTRACT

Measurements of panicle number concentrations in different vehicles (tram, Mass Transit Railway, and air-conditioned and non air-conditioned franchisee) buses) were carried out from July 1 to November 1, 1994, in Hong Kong. A total of 320 samples in 14 days were collected for four count median diameters (0.3, 0,5, 5.0, and 10.0 um). The total particle number concentrations of airborne paniculate matter exposed to commuters varied from 3.61E6 to 7.68E7 ft for particle diameter 0.3 um or greater. The concentrations were much higher, from 4 to 16 times, than those (8.02E5 to 4.60E6 ft ) in rural areas (at the seaside near Hong Kong University of Science Technology), but the concentrations in non air-conditioned transportation (trams and franchised buses) were closer to those in the streets. It was found that the number concentrations of fine particles (0.3 to 5 mm) were relatively constant, and the fine particles could not be filtered by the air-conditioners used.     

IRRADIATION OF INDUSTRIAL ENZYME PREPARATIONS II. CHARACTERIZATION OF FUNGAL PECTINASE BY THIN-LAYER ISOELECTRIC FOCUSING AND GEL FILTRATION

Industrial dry fungal pectinase from A. niger was irradiated with doses (up to 1 Mrad) of ⁶⁰ Co-γrays effective in reducing microbial contamination. The pectinase was characterized by thin-layer isoelectric focusing and gel filtration in order to detect possible radiation-induced structural alterations. Thin-layer isoelectric focusing revealed at least fifteen multiple forms with pectin-depolymerizing activity, with isoelectric points in the range pH 4.5–7. Heterogeneity of pectinesterase was also demonstrated, the main band occurring around pH 4. By thin-layer gel filtration the molecular weight of the pectin-depolymerase was estimated as being about 36,000, and that of pectinesterase as about 33,000. Radiation-induced changes of the charge properties or molecular size of the irradiated pectinase preparation were not observed. The feasibility of using ionizing radiation for the reduction of microbial contamination of industrial enzyme preparations looks promising.     

The aerobic microflora of the Scotch haggis

The aerobic microflora of freshly purchased Scotch haggis was dominated by organisms identified with Bacillus. Lactobacillus, Staphylococcus , yeasts and moulds were also detected in significant numbers. On storage at 5,30 or 37°C for 3 weeks, spoilage of the haggis was accompanied by a drop in pH and a tenfold increase in numbers of general contaminants and lactic acid bacteria.     

Relation of Load to Radial Crack Length for Spherical Indentations in Hot-Pressed ZnS

Hot-pressed ZnS was indented by spherical indenters of various radii. The relation of the load (P) and radial crack length ( c_r ) was better modeled by Pαic_r^½ , where d_i is the indentation diameter, than by Pαc_r^3/2 .     

Ba2Ti9O20 Phase Equilibria

The heterogeneous phase distribution found in Ba₂Ti₉O₂₀ ceramic resonators results from a temperature-dependent phase boundary and slow reaction kinetics. When sintered at 1350°C or higher in oxygen the Ba₂Ti₉O₂₀ phase becomes slightly reduced and barium-rich. Thus a stoichiometric composition forms rutile and "Ba₂Ti₉O₂₀'phase. On slow cooling the excess barium diffuses to the oxygen-rich surface where it reacts to form an envelope of rutile-free material surrounding a core containing a small amount of rutile.     

Comparison of Single-Point and Multipoint Grinding Damage in Glass

Glass plates were damaged by single-point and multipoint grinding at various set depths and wheel speeds to evaluate the usefulness of single-point grinding to simulate the mechanisms of damage penetration and material removal during multipoint grinding. The observed damage was much more severe in single-point than in multipoint grinding. In both single-point and multipoint grinding, the vertical load (P_v) dependence of the crack depth (c) P_v∞ c^1.2. In glass, the effect of the residual stresses in reducing the remaining strengths of the damaged bars was less than that observed for other ceramics previously investigated, mainly because much of the irreversibly deformed zone was removed by crushing. The advantages and disadvantages of using single-point grinding to simulate multipoint grinding are discussed.     

Plant-mediated biosynthesis of silver nanoparticles by leaf extracts of <Emphasis Type="Italic">Lasienthra africanum</Emphasis> and a study of the influence of kinetic parameters

Lasienthra africanum (LA) leaf extract was employed for nano-silver synthesis. The reducing effect of the plant extract was investigated at different times, pH, temperatures and concentrations. The effect of various kinetic parameters was studied using UV–vis spectroscopy. Blue-shifted surface plasmon bands indicating smaller sized nanoparticles were obtained at neutral pH (6.8–7.0), temperature of 65°C and concentration ratio of 1:10 (leaf extract: AgNO₃) with increasing reaction times under the reaction conditions. The kinetics of the reaction followed pseudo-first- and -second-order rate equations, and was thermodynamically favoured at higher time. Spherically shaped nanoparticles were obtained at different reaction conditions.     

Quaternary System U-C-O-N at 1700°C: Phase Relations in the Low-Nitrogen Region

Phase relations in the system U-C-O-N at 1700°C were established at nitrogen levels up to an atomic ratio N: C 1:3 by microstructural and X-ray analyses of sintered powder compacts. The extent of the solid-solution field of uranium oxycarbonitride was established on the ternary plane U-C_0.75No._0.25-O. The maximum solubility of oxygen in the solid solution is 14 at.%, corresponding to a composition U_0.50C_0.27O _0.14N_0.09 compared to 17 at.% on the U-C-O plane. Nine other phase fields were established on the U-C-O C_0.75N_0.25-O plane, all of which contain a uranium oxycarbonitride solid-solution phase and a gaseous phase of CO and N.₂. Equilibrium pressure varies from about 0.01 torr in phase fields containing free uranium to about 200 torr in the field containing solid solution +"UC₂" (oxy-gen-containing dicarbide) + C + UO₂. Lattice parameters of the solid-solution phase were determined. A field containing solid solution and UzC3 exists to about 3.5 at.% O and 2 at.% N at the hyperstoichiometric boundary of the solid-solution field. An isothermal phase diagram for the low-nitrogen region of the U-C-O-N system is proposed.