Showing papers by "Ganesan Narsimhan published in 2018"

Role of Proteins on Formation, Drainage, and Stability of Liquid Food Foams

Abstract: Foam is a high-volume fraction dispersion of gas into a liquid or a solid. It is important to understand the effect of formulation on shelf life and texture of food foams. The objective of this review is to elucidate mechanisms of formation and stability of foams and relate them to the formulations. Emulsifiers are important in foam formation, whereas proteins are generally preferred to provide long-term stability. Syneresis in foams is a precursor to their collapse in many instances. Intermolecular forces, conformation, and flexibility of proteins play an important role in foam stabilization. An adsorbed protein layer at air/water interfaces imparts interfacial rheology that is necessary to improve the shelf life of foam products. Wettability and spreading of food particles at the interface can stabilize or destabilize foams, depending on their properties. More studies are needed to fully understand the complex interplay of various mechanisms of destabilization in a real-food formulation.

Characterization of Interactions between Curcumin and Different Types of Lipid Bilayers by Molecular Dynamics Simulation.

Abstract: Curcumin (CUR) is a natural food ingredient with known ability to target microbial cell membrane. In this study, the interactions of CUR with different types of model lipid bilayers (POPE, POPG, POPC, DOPC, and DPPE), mixtures of model lipid bilayers (POPE/POPG), and biological membrane mimics (Escherichia coli and yeast) were investigated by all-atom explicit solvent molecular dynamics (MD) simulation. CUR readily inserts into different types of model lipid bilayer systems in the liquid crystalline state, staying in the lipid tails region near the interface of lipid head and lipid tail. Parallel orientation to the membrane surface is found to be more probable than perpendicular for CUR, as indicated by the tilt angle distribution. This orientation preference is less significant as the fraction of POPE is increased in the system, likely due to the better water solvation of perpendicular orientation in the POPE bilayer. In E. coli and yeast bilayers, tilt angle distributions were similar to that for POPE/P...

Investigation of the interaction of amyloid β peptide (11–42) oligomers with a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane using molecular dynamics simulation

Abstract: Some amyloid related proteins/peptides are involved in aggregation and pore formation in phospholipid membranes (cell membranes), which result in a variety of neurological disorders such as Alzheimer's disease, Parkinson's disease and Huntington disease. In this research, the mechanism of pore formation by β amyloid (Aβ) peptides was investigated using molecular dynamics simulation by simulating the interaction of the Aβ(11-42) peptide, with a lipid membrane and the potential of the mean force of interaction was evaluated. A 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane system with different cholesterol concentrations was used to simulate the neural cell membrane. The results indicated that Aβ(11-42) peptide oligomers with peptide numbers larger than two were more likely to lead to lipid deformation and water channels, and the free energy of penetration into the membrane decreased with the increasing number of peptides. Increasing the concentration of cholesterol leads to a higher energy barrier for the penetration of peptide into the lipid bilayer thereby protecting the membrane. The results of this research have potential application in the prevention of pore formation by Aβ aggregates on the lipid membrane.

Synergistic effect of low power ultrasonication on antimicrobial activity of cecropin P1 against E. coli in food systems

Abstract: Recent studies have shown that both low frequency (20–100 kHz) ultrasonication and antimicrobial peptides (AMPs) treatment processes have a significant advantage in inactivating bacterial cells than the conventional heat treatment due to higher food texture quality of the final product. However, the effect of the combined process has not been fully investigated in complex matrices such as food. In this study, deactivation of Escherichia coli in different concentrations of milk and orange juice were performed using three different treatments: low frequency ultrasonication (20 kHz) at different power levels, antimicrobial peptide Cecropin P1 at different concentrations, and combination of both. The results of all samples showed that the combined treatment is more efficient, reducing the cell density of E. coli up to four orders of magnitude, compared to individual treatments. However, the milk concentration results in lower synergistic effect. This is believed to be due to complexation of milk proteins with Cecropin P1 thus resulting in less availability of the latter for antimicrobial action. This dependence was not observed in orange juice samples. Ultrasonication resulted in insignificant decrease in viscosity, color and vitamin C for both milk and orange juice except at higher power level of 160 W at longer exposure time.

Impacts of Size and Deformability of β-Lactoglobulin Microgels on the Colloidal Stability and Volatile Flavor Release of Microgel-Stabilized Emulsions.

Abstract: Emulsions can be prepared from protein microgel particles as an alternative to traditional emulsifiers Prior experiments have indicated that smaller and more deformable microgels would decrease both the physical destabilization of emulsions and the diffusion-based losses of entrapped volatile molecules The microgels were prepared from β-lactoglobulin with an average diameter of 150 nm, 231 nm, or 266 nm; large microgels were cross-linked to decrease their deformability Dilute emulsions of 15⁻50 μm diameter were prepared with microgels by high shear mixing Light scattering and microscopy showed that the emulsions prepared with larger, untreated microgels possessed a larger initial droplet size, but were resistant to droplet growth during storage or after acidification, increased ionic strength, and exposure to surfactants The emulsions prepared with cross-linked microgels emulsions were the least resistant to flocculation, creaming, and shrinkage All emulsion droplets shrank as limonene was lost during storage, and the inability of microgels to desorb caused droplets to become non-spherical The microgels were not displaced by Tween 20 but were displaced by excess sodium dodecyl sulfate Hexanol diffusion and associated shrinkage of pendant droplets was not prevented by any of the microgels, yet the rate of shrinkage was reduced with the largest microgels