Factors Influencing the Production and Activity of a Streptococcus thermophilus Lipase

The cells from 32 strains were disrupted by pressure. All the strains except two showed lipase activity. Optimum temperature for lipase production was 44°C. Production of lipase was inhibited by addition of butter oil (29%), milk (41%) and casein (12%) and stimulated by soybean oil (39%), cream (27%) and corn oil (21%) to the medium. The enzyme was stable when stored at 37°C and 45°C for 1 wk. The enzyme was partially inactivated by pasteurization treatment (65°C/30 min). Optimum temperature and pH for lipase activity was 45°C and 9.0, respectively. The enzyme was relatively more active toward tributryin than toward natural lipids.     

THE USE OF OZONATION TO REDUCE THE POTENTIAL FOR FORMING TRIHALOMETHANE COMPOUNDS IN CHLORINATING RESORCINOL,PHLOROGLUCINOL AND 1,3 CYCLOHEXANEDIONE

This study concerns the ozonation of Resorcinol, Phloroglucinol and 1,3 Cyclohexanedione in the presence of bromide ion in a bubble column, prior to chlorination. Preozonation in aqueous solutions reduces the potential for forming chlorinated trihalomethane compounds. At organic concentrations greater than 10^?4?M a short ozonation time increases the potential for forming trihalo compounds. At longer ozonation times the reverse is true. Finally the influence of mass transfer and chemical reaction on the ozone absorption rate have been evaluated following the film theory.     

SODIUM BICARBONATE AND THE MICROSTRUCTURE, EXPANSION AND COLOR OF EXTRUDED BLACK BEANS

Seed microstructure provides complementary information to physicochemical determinations. Scanning electron micrographs of cross sections of black bean extrudates illustrated the increase in volume expansion, with an increase of sodium bicarbonate (NaHCO ₃ ) in the extrudate. This increase in volume expansion is attributed to the increase in air cell size and corresponding decrease in air cell wall thickness with additional concentrations of NaHCO ₃ . The measured increase in diameter and expansion ratio of extrudates with NaHCO ₃ addition may be explained by the increase in number of air cells within the extrudate and the increase in pores in the gelatinized starch matrix of air cell walls. Extrusion conditions, which involved the use of heat and moisture, provided the necessary conditions for the release of CO ₂ from NaHCO ₃ during processing. Expansion ratio increases between the control extrudate, and extrudate with 0.5% NaHCO ₃ addition were twofold at the node and 1.8‐fold at the area between the nodes. Statistical analysis of color data exhibited no significant change in L*, hue or chroma across concentrations of NaHCO ₃ for nonextruded flours. A simple linear regression adequately described changes in L* and hue for extruded flours. However, a curvilinear relationship was needed to explain changes in chroma versus NaHCO ₃ for extruded flours, making changes in chroma measurements less easy to interpret. The color data in this study serve as primary information for future establishment of cut‐off values of color for the development of an acceptable legume snack.     

Isolation and Partial Characterization of a Natural Antioxidant from Shrimp (Pandalus jordani)

The nature of a natural antioxidant present in shrimp was investigated. From several solvents used in the extraction process, ethanol proved most effective. A diethyl ether extract exhibited no antioxidant activity. The compound responsible for the antioxidant effect was present in very low concentrations in its natural source. The chemical characteristics and chromatographic properties suggested that it was a polyhydroxylated derivative of an aromatic amino acid.     

Lipid Protein Interactions in Offal Protein Isolates: Effect of Several Solvents on Lipid Extraction

The effect of solvents of increasing polarity on lipid extraction of bovine lung and rumen proteins, isolated by two different procedures, namely, alkaline solubilization of the protein followed by its isoelectric precipitation, and sodium dodecyl sulfate solubilization of the protein and its subsequent precipitation by ferric chloride was studied. A hyperbolic relationship was observed between the amount of lipid extracted and the dielectric constant of the solvent used. This relationship was described by an equation which allowed the calculation of the total amount of lipids present in the isolates and the average intensity of the interaction between lipids and proteins in each system. Relative composition of fatty acids in lung isolates showed marked dependence on the polarity of the solvent employed.     

THE COMBINATORIAL ANT SYSTEM

This paper presents a new distributed algorithm based on Ant System (AS) concepts called Combinatorial Ant System (CAS). It is oriented to solve static discrete-state combinatorial optimization problems. Our approach consists of mapping the solution space of the combinatorial optimization problem in the space where the ants will walk, and defining the transition probability and the pheromone update formula of the Ant System, according to the objective function of the Combinatorial Optimization Problem. We test our approach on the graph partitioning, graph coloring and traveling salesman problems.     

Robustness considerations for p-step matrix integrators with uncertainty in the continuous system mode

Robustness measures for p-step matrix integrators are established. These measures are the quantitative bounds for either structured or unstructured perturbations existing in continuous-time systems to ensure that discrete versions of those systems obtained using p-step matrix integrators remain stable. Examples are given to illustrate the usefulness of the proposed measures. The effect of the sampling time T, the choice of the discretizing scheme, and the integrator step size on these robustness measures is discussed through examples.     

Influence of Impurities on High-Temperature Reactions of Kaolinite

When kaolinite is heated for differential thermal analysis (DTA) the second exothermic peak (∼1275°C) is due to growth of mullite crystals accelerated by formation of a liquid phase. The third exothermic peak (∼1460°C) is due to crystallization of cristobalite. Addition or presence of impurity oxides causes the second peak to shift in temperature and accelerates the formation of cristobalite so that the third peak may appear as low as the second exothermic peak temperature.