Stabilization of foams and emulsions by mixtures of surface active food-grade particles and proteins

Surface active biopolymers such as proteins can form films with particularly high interfacial elasticities and viscosities and these molecules are widely exploited as foaming and emulsifying agents in foods. Solid particles of the correct size and wetting characteristics can also be extremely effective stabilizers of foams and emulsions, although the underlying mechanism of stabilization is somewhat different. Relatively little is known about what happens when both surface active polymers and surface active particles are present together. This work presents recent findings on the effects of mixtures of proteins plus novel food-compatible surface active particles. The proteins include caseins and whey proteins. The surface active particles prepared include cellulose + ethyl cellulose complexes, hydrophobically-modified starch granule particles and stable (non-spreading) protein-stabilized oil droplets. Interfacial shear rheology of adsorbed films was measured via a biconical bob apparatus and interfacial dilatational rheology was measured via a Langmuir trough type apparatus. The corresponding stability of bubbles to coalescence and disproportionation was assessed in separate experiments. Stability of oil-in-water emulsions was assessed via measurement of particle size distributions as function of time and visual assessment of the tendency to creaming and oiling off. In general, it is shown that the surface active particles on their own exhibit much lower measures of interfacial elasticity and viscosity than the proteins, but in combination with the proteins they appear to enhance the interfacial viscoelasticity considerably, with concomitant increases in bubble and emulsion droplet stability. There is little evidence of attractive interactions between the particles and the proteins, so a possible explanation of the increased stability is that the proteins increase the accumulation of particles at the interface, giving rise to increased jamming of particles at the interface.     

Investigation on carbon nanomaterials: Coaxial CNT-cylinders and CNT-polymer composite

The macroscopic coaxial carbon cylinders (dia. ∼0.5 cm with varying lengths, ∼ 7–10 cm) consisting of aligned carbon nanotube (CNT) stacks have been prepared by controlled spray pyrolysis method. The coaxial carbon cylinders of CNT stacks have been formed directly inside the quartz tube. Another study is done on multi-walled CNTs (MWNTs)-polymer (e.g. polyethylene oxide (PEO), polyacrylamide (PAM)) composite films. We have investigated the structural, electrical and mechanical properties of MWNTs-PEO composites. Composites with different wt% (between 0 and 50 wt% of MWNTs) have been prepared and characterized by the scanning electron microscopic technique. Enhanced electrical conductivity and mechanical strength were observed for the MWNTs-PEO composites. We have also studied the electrical property of MWNTs-PAM composite films.     

Mechanical response and multilevel structure of biomimetic hydroxyapatite/polygalacturonic/chitosan nanocomposites

Using an in situ mineralization process that is biomimetic we have synthesized new nanocomposites of chitosan/hydroxyapatite in 50–50 ratio(ChiHAP50), polygalacturonic acid/hydroxyapatite in 50–50 ratio (PgAHAP50) and Chitosan/hydroxyapatite/Polygalacturonic acid (ChiPgAHAP50). Polygalacturonic acid (PgA) is electrostatically complementary to chitosan, and thus is expected to provide stronger interfacial interactions and improve mechanical response. Atomic force imaging of fractured and polished surfaces suggests a multilevel organization in the hydroxyapatite/biopolymer nanocomposite. The AFM images of ChiPgAHAP50 nanocomposite display presence of chitosan rich and polygalacturonic rich domains. These chitosan rich and PgA rich domains are made of smaller globular shaped particles in which, hydroxyapatite nano-particles are embedded in the biopolymer matrix. The average size of the hydroxyapatite particles in PgAHAP50, ChiHAP50 and ChiPgAHAP50 were found to be 25, 42 and 34 nm respectively. The elastic moduli determined from nanoindentation of PgAHAP50, ChiHAP50 and ChiPgAHAP50 composites are 29.81, 17.56 and 23.62 GPa respectively. Hardness values of the three composites in the same order were found to be 1.56, 0.65 and 1.14 GPa respectively. Macro-mechanical tests showed significant enhancement in elastic moduli, strain to failure and compressive strength of ChiPgAHAP50 composites over ChiHAP50 and PgAHAP50.     

Relationship between mechanisms and activities at the time of pedestrian injury and activity limitation among school adolescents in Kathmandu, Nepal

This study assessed the relationship between pedestrian activity at the time of injury, the type of vehicle involved and resulting activity limitation among school adolescents in the Kathmandu and Lalitpur districts of Nepal. A cross-sectional study of 1557 students in grades 6–8 across 14 schools was conducted using a self-administered questionnaire from August to September 2003. Twenty-three percent of adolescents reported pedestrian injuries, 38% were from urban and 21% from semi-urban areas. Adolescents were commonly injured by motorcycles and motor vehicles while crossing the road; however, while walking and playing, they were commonly injured by bicycles and motorcycles. Bicycles and motor vehicles were less likely to be involved in injury while crossing the roads and playing, respectively (p < 0.001). Activity was more likely to be limited for a longer period of time (>7 days) with injuries endured while crossing the road (p < 0.001). In urban areas, boys and girls were more likely to be injured while crossing the road and walking, respectively (p < 0.05), and both were commonly injured by motorcycles. In semi-urban areas, boys and girls were commonly injured while walking and were more likely to be injured by motorcycles and bicycles, respectively (p < 0.05). In both areas, more boys than girls were injured while playing. These findings have important implications for pedestrian safety interventions in poor countries.     

Bioavailability of Micronutrients from Plant Foods: An Update

Deficiencies of iron, zinc, iodine and vitamin A are widespread in the developing countries, poor bioavailability of these micronutrients from plant-based foods being the major reason for their wide prevalence. Diets predominantly vegetarian are composed of components that enhance as well as inhibit mineral bioavailability, the latter being predominant. However, prudent cooking practices and use of ideal combinations of food components can significantly improve micronutrient bioavailability. Household processing such as heat treatment, sprouting, fermentation and malting have been evidenced to enhance the bioavailability of iron and β-carotene from plant foods. Food acidulants amchur and lime are also shown to enhance the bioavailability of not only iron and zinc, but also of β-carotene. Recently indentified newer enhancers of micronutrient bioaccessibility include sulphur compound-rich Allium spices—onion and garlic, which also possess antioxidant properties, β-carotene-rich vegetables—carrot and amaranth, and pungent spices—pepper (both red and black) as well as ginger. Information on the beneficial effect of these dietary compounds on micronutrient bioaccessibility is novel. These food components evidenced to improve the bioavailability of micronutrients are common ingredients of Indian culinary, and probably of other tropical countries. Fruits such as mango and papaya, when consumed in combination with milk, provide significantly higher amounts of bioavailable β-carotene. Awareness of the beneficial influence of these common dietary ingredients on the bioavailability of micronutrients would help in devising dietary strategies to improve the bioavailability of these vital nutrients.     

Existence and Global Asymptotic Stability of Fuzzy Cellular Neural Networks with Time Delay in the Leakage Term and Unbounded Distributed Delays

Fuzzy cellular neural network (FCNN) structures are based on the uncertainties in human cognitive processes and in modeling neural systems, and they provide an interface between a human expert and classical cellular neural networks (CNNs). In this paper, an existence and global asymptotic stability analysis of the equilibrium point of FCNNs with time delay in the leakage term and unbounded distributed delays is investigated. Based on the Lyapunov-Krasovskii functional with free-weighting matrix, and using the homeomorphism mapping principle and linear matrix inequalities (LMIs), a new set of stability criteria for FCNNs is obtained with time delay in the leakage term, time-varying delays and unbounded distributed delays. The proposed results can be easily checked via the LMI Control Toolbox in MATLAB. Moreover, it is well known that the stability behavior of FCNNs is very sensitive to the time delay in the leakage term. In the absence of the leakage term, a new stability criterion is also derived by employing a Lyapunov-Krasovskii functional using an LMI approach. Numerical examples are provided to illustrate the effectiveness and reduced conservativeness of the developed techniques.     

Recycled waste paper—A new source of raw material for electric double-layer capacitors

For the first time, a new carbon–carbon composite electrode material for supercapacitors is prepared by simple KOH activation of waste newspaper. The amorphous nature and surface morphology of the carbon composite are investigated by X-ray diffraction (XRD), N₂ adsorption/desorption and scanning electron microscopy. The surface area and pore diameter are 416 m² g⁻¹ and 5.9 nm, respectively. Electrochemical characteristics are evaluated by cyclic voltammetry (CV) and charge–discharge tests in 6.0 M KOH at a 1 mA cm⁻² current density. The CV results reveal a maximum specific capacitance of 180 F g⁻¹ at a 2 mV s⁻¹ scan rate and the data explore a development of new use for waste paper into a valuable energy storage material.     

Geochemical evidences of trace metal anomalies for finding hydrocarbon microseepage in the petroliferous regions of the Tatipaka and Pasarlapudi areas of Krishna Godavari Basin, India

The long-term seepage of hydrocarbons, either as macroseepage or microseepage, can set up near-surface oxidation reduction zones that favor the development of a diverse array of chemical and mineralogical changes. The bacterial oxidation of light hydrocarbons can directly or indirectly bring about significant changes in the values of pH and Eh of the surrounding environment, thereby also changing the stability fields of the different mineral species present in that environment. The paper reports the role of hydrocarbon microseepage in surface alterations of trace metal concentrations. In this study trace metal alterations were mapped that appear to be associated with hydrocarbon microseepages in the oil/ gas fields. A total of 50 soil samples were collected near oil and gas fields of the Tatipaka and Pasarlapudi areas of the Krishna Godavari Basin, Andhra Pradesh. The soil samples were collected from a depth of 2-2.5 m. The paper reports the chemical alterations associated with trace metals in soils that are related to hydrocarbon microseepages above some of the major oil and gas fields of this petroliferous region. Trace metals, such as scandium (Sc), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), barium (Ba) and strontium (Sr), in soil samples were analyzed using inductively coupled plasmamass spectrometry (ICP-MS). The concentrations of Sc (8 to 40 mg/kg), V (197 to 489 mg/kg), Cr (106 to 287 mg/kg), Co (31 to 52 mg/kg), Ni (65 to 110 mg/kg), Cu (88 to 131 mg/kg), Zn (88 to 471 mg/kg), Ba (263 to 3,091 mg/kg) and Sr (119 to 218 mg/kg) were obtained. It was observed that the concentrations of trace elements were tremendously increased when they were compared with their normal concentrations in soils. The analysis of adsorbed soil gas showed the presence of high concentrations of ΣC 2+ (C 2 H 6 , C 3 H 8 and n-C 4 H 10 ) ranging from 7 to 222 μg/kg respectively. Integrated studies of trace elements over adsorbed light gaseous hydrocarbons (ΣC 2+ ) anomalies showed good correlation with the existing oil and gas wells. The carbon isotopic composition of δ 13 C 1 of the samples ranges between -36.6‰ to -22.7‰ (Pee Dee Belemnite) values indicate thermogenic origin, which presents convincing evidence that the adsorbed soil gases collected from these sediments are of catagenetic origin. The increase in the concentrations of trace metals near oil/gas producing areas, suggests a soil chemical change to a reducing environment, presumably due to the influence of hydrocarbon microseepage, which could be applied with other geoscientific data to identify areas of future hydrocarbon exploration in frontier areas.