ABSTRACT
Pulsed light (PL) inactivation kinetics of Escherichia coli K-12, Clostridium sporogenes and Geobacillus stearothermophilus were evaluated under different treatment conditions. The PL system was factory set to operate at three pulses per second with a pulse width of 360 µs exposing samples placed on one of the 9 trays on a rack. Two PL parameters were evaluated in the study: number of pulses (a time factor) and the tray position (a spatial distance factor) both influencing the amount of light energy absorbed. As expected, the level of microbial inactivation increased with an increase in the number of pulses (from 1 to 15) and decreased with an increase in the Spatial distance (Tray # 1 to 9) away from the light source. Both the number of pulses and spatial distance as well as their interactions were found to have a significant effect (P < 0.05) on the extent of microbial inactivation. Vegetative cells of E. coli were most sensitive to PL treatment with a maximum 5 logarithmic reductions on Tray 1 after a 12-pulse treatment (4 s). G. stearothermophilus was more resistant to PL than C. sporogenes. Overall, the PL treatments (12-15 pulses) achieved a minimum four logarithmic reductions in the populations of all three microorganisms on the top tray at doses still below 12 J/cm2, the FDA-approved limit.
ABSTRACT
Electrospun film is developed from an electrically charged ultrafine jet of a polymer solution or melt as a matrix of thin/nano fibers struck on to a target surface. The objective of this work was to obtain homogeneous nanofibers from pea protein isolate (PPI) in polyvinyl alcohol (PVA) by hybrid electrospinning as well as incorporating cinnamaldehyde (CA) into the matrix to obtain an antibacterial mat. The effect of processing conditions, pH, polymer and CA concentrations on formulation properties and nanofiber morphology were investigated and the mats were visualized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Rheological evaluation indicated a pseudoplastic behavior for all formulations. Alkaline pH formulation led to a decreasing apparent viscosity and an increasing electrical conductivity resulting in the formation of more homogeneous fibers. The 50:50 mass percentage ratio of PPI/PVA solutions produced homogeneous nanofibers with the average fiber diameter of 485⯱â¯85â¯nm. FTIR spectroscopy confirmed uniform dispersion of PPI and PVA. The minimum concentration of CA to inhibit both Gram negative and Gram positive bacteria was 1%. The average diameter of nanofibers decreased from 257⯱â¯51â¯nm to 219⯱â¯31â¯nm by increasing CA content from 0.25 to 1.5%.
