Ganesan Narsimhan

Bio: Ganesan Narsimhan is an academic researcher from Purdue University. The author has contributed to research in topic(s): Adsorption & Emulsion. The author has an hindex of 34, co-authored 140 publication(s) receiving 3465 citation(s). Previous affiliations of Ganesan Narsimhan include Monash University, Clayton campus & Monash University.

A model for transitional breakage probability of droplets in agitated lean liquid-liquid dispersions

Abstract: A model for transitional breakage probability of droplets in agitated lean fiquid-liquid dispersions is proposed based on the mechanism of breakage of droplets due to their oscillations resulting from relative velocity fluctuations. A universal transitional breakage probability in terms of non-dimensionalized drop diameter is derived for all dispersed phases whose density and viscosity are almost the same as that of continuous phase. The maximum stable drop diameter ds derived from the model, shows a dependence of NWe−0.6. It is shown that a “power law” approximation Kvn is valid for transitional breakage probability for d/ds up to 2. The exponent 2.67, predicted by this model corresponds rather well with an estimate of 2, obtained from experimental observations. A functional relation for the rate constant K in terms of the parameters and physical properties of the system is derived. A universal non-dimensionalized equilibrium drop-size distribution for agitated lean liquid-liquid dispersions is derived by analytical solution of a population balance equation simplified by order of magnitude estimates. Interestingly enough, this analytical solution is the same as the Gaussian distribution suggested empirically by Chen and Middleman.

Effect of thermal treatment on interfacial properties of β-lactoglobulin

Abstract: The changes in the secondary conformation and surface hydrophobicity of β-lactoglobulin subjected to different thermal treatments were characterized at pH values of 7, 5.5 and 4 using circular dichroism (CD) and hydrophobic dye binding. Heating resulted in a decrease in α-helix content with a corresponding increase in random coil at all pH values, this change being more pronounced for small heating times. Heating also resulted in an increase in surface hydrophobicity as a result of partial denaturation, this increase being more pronounced at pH 4. Thermal treatment resulted in a shift of the spread monolayer isotherm at air–water interface to smaller area per molecule due to increased flexibility and more loop formation. Thermal treatment led to an increase in interfacial shear elasticity and viscosity of adsorbed β-lactoglobulin layer at pH 5.5 and 7. Interfacial shear elasticity, shear viscosity, stability of β-lactoglobulin stabilized emulsion and average coalescence time of a single droplet at a planar oil–water interface with adsorbed protein layer exhibited a maximum for protein subjected to 15 min heat treatment at pH 7. At pH 5.5, the interfacial shear rheological properties and average single drop coalescence time were maximum for 15 min heat treatment whereas emulsion stability was maximum for 5 min heat treatment. At pH 7, thermal treatment was found to enhance foam stability. Analysis of thin film drainage indicated that interfacial shear rheological properties do not influence thin film drainage.

Designing carbohydrate nanoparticles for prolonged efficacy of antimicrobial peptide.

Abstract: In this work, carbohydrate nanoparticles were created to prolong the efficacy of antimicrobial peptide against pathogens. Nisin and Listeria monocytogenes were used as the peptide and pathogen models, respectively, and phytoglycogen (PG)-based nanoparticles were developed as carriers of nisin. PG from su1 mutant maize was subjected to β-amylolysis as well as subsequent succinate or octenyl succinate substitutions. The goal was to minimize the loss of peptide during storage and meanwhile realize an effective release in the presence of bacteria. The capabilities of PG derivatives as carriers of nisin were evaluated using centrifugal ultrafiltration, zeta-potential, and the initial availability of nisin against L. monocytogenes. All methods indicated that nisin loading was favored by a high degree of substitution (DS), presence of hydrophobic octenyl moiety, and β-amylolysis of PG nanoparticles. To evaluate the prolonged nisin efficacy, preparations containing nisin and PG derivatives were loaded into a BHI-agar deep-well model (mimicking nisin depletion at the nutrient-containing surface). The residual inhibitory activities of preparations against L. monocytogenes were monitored during 21 days of storage at 4 °C. The results showed that all PG derivatives led to the prolonged retention of nisin activity and the longest retention was associated with high DS, β-amylolysis, and octenyl succinate. Evidently, both electrostatic and hydrophobic interactions are the driving forces of nisin adsorption, and the glucan structure at the nanoparticle surface also affects nisin loading and retention during storage.

Droplet breakage in stirred dispersions. Breakage functions from experimental drop-size distributions

Abstract: Transient breakage drop-size distributions have been experimentally measured using an image analysis technique The transient distributions show self-similar behavior The breakage rate and daughter-drop distribution functions have been determined using an inverse-problem approach which takes advantage of this self-similarity The inverse-problem results show that the breakage rate is not a power law function of the drop size The breakage rate is found to increase sharply with the drop size and the stirrer speed while decreasing sharply with increase in the interfacial tension It is also found to decrease with increase in the dispersed phase viscosity, though the dependence on the viscosity is weaker than on the other variables The daughter drop distribution was found to be relatively insensitive to the stirrer speed and interfacial tension, but was found to depend on the dispersed phase viscosity As the drop viscosity increases, the breakage becomes more erosive in nature, leading to a broader size distribution of daughter drops Generalized correlations for the breakage rate and daughter-drop distribution which account for the effect of physical properties and experimental conditions are presented These relations will be very useful in predicting the drop-size distributions in stirred dispersions Models for the breakage functions are compared with those determined in this study and the model predictions of the transient-size distributions are compared with the experimental data

Effect of composition and pore structure on binding energy and effective diffusivity of moisture in porous food

Abstract: Food samples of different compositions were formulated by extruding mixtures of starch and gluten of different compositions, whereas samples of varying pore structure were obtained through extrusion of durum semolina at 57 and 137°C. Experimental measurement of desorption isotherm of these samples at different temperatures in the range 25–40°C indicated that the water binding ability was fairly insensitive to the pore structure of food samples and was found to be lower for extruded and pregelatinized samples as well as for samples of higher gluten content. Experimental desorption isotherm data were represented by the Oswin equation in order to evaluate moisture binding energy as a function of moisture content and temperature by employing the Clausius-Clapeyron equation. Binding energy was found to be negligible at high moistures (above 0·2 d.b.), increasing at lower moisture contents, lower temperatures and higher starch contents. Effective diffusivity of moisture through the porous food at different moisture contents and temperatures was inferred from drying curves in the temperature range 60–105°C. Effective diffusivity (D eff ) was higher in pregelatinized samples and was found to be much higher through porous puffed pasta than regular pasta. The effect of composition on D eff was confounded by the effect of pore structure as a result of variations in pore size distribution in the extruded samples of different compositions. The decrease in D eff at lower moisture contents was postulated to be due to the decrease in the available free water for diffusion and was explained through a simple model which related the available free moisture to the binding energy.

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Abstract: In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Bio-nanocomposites for food packaging applications

Abstract: There is growing interest in developing bio-based polymers and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis. Bio-nanocomposites open an opportunity for the use of new, high performance, light weight green nanocomposite materials making them to replace conventional non-biodegradable petroleum-based plastic packaging materials. So far, the most studied bio-nanocomposites suitable for packaging applications are starch and cellulose derivatives, polylactic acid (PLA), polycaprolactone (PCL), poly(butylene succinate) (PBS) and polyhydroxybutyrate (PHB). The most promising nanoscale fillers are layered silicate nanoclays such as montmorillonite and kaolinite. In food packaging, a major emphasis is on the development of high barrier properties against the diffusion of oxygen, carbon dioxide, flavor compounds, and water vapor. Moreover, several nanostructures can be useful to provide active and/or smart properties to food packaging systems, as exemplified by antimicrobial properties, oxygen scavenging ability, enzyme immobilization, or indication of the degree of exposure to some detrimental factors such as inadequate temperatures or oxygen levels. Challenges remain in increasing the compatibility between clays and polymers and reaching complete dispersion of nanoparticles. This review focuses on the enhancement of packaging performance of the green materials as well as their biodegradability, antimicrobial properties, and mechanical and thermal properties for food packaging application. The preparation, characterization and application of biopolymer-based nanocomposites with organic layered silicate and other fillers, and their application in the food packaging sector are also discussed.

Population Balances: Theory and Applications to Particulate Systems in Engineering

Abstract: Foreword. Preface. Introduction. The Framework of Population Balances. Birth and Death Functions. The Solution of Population Balance Equations. Similarity Behavior of Population Balance Equations. Inverse Problems in Population Balances. The Statistical Foundation of Population Balances. Index.

Combustion aerosols: factors governing their size and composition and implications to human health.

Abstract: Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 μm (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-tem-perature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated t...