Effect of ultraviolet (UV-C) radiation on spores and biofilms of Alicyclobacillus spp. in industrialized orange juice.

Bacteria of the genus Alicyclobacillus pose serious quality problems for the juice processing industries that have sought effective alternatives for its control. The present study evaluated the effect of UV-C radiation on the reduction of spores and biofilm formation of Alicyclobacillus spp. on stainless steel and rubber surfaces using industrialized orange juice as a culture medium. Four reference Alicyclobacillus spp. species and different UV-C dosages were investigated. After exposed for 20 min (16.8 kJ/m2) to UV-C, the spores of Alicyclobacillus acidoterrestris, Alicyclobacillus herbarius, and Alicyclobacillus cycloheptanicus decreased drastically more of 4 log CFU/mL, with counts below the detection limit of the method (<1.7 log CFU/mL), while the Alicyclobacillus acidocaldarius spores were more sensitive to UV-C, once this spore reduction was observed within 15 min (12.6 kJ/m2). Morphological changes in the Alicyclobacillus acidoterrestris spores were observed by scanning electron microscopy. A reduction of biofilm formation was observed for all UV-C treatments, and the higher reductions (approximately 2 log CFU/mL) were found for the Alicyclobacillus acidocaldarius species after 30 min (26.2 kJ/m2), on the stainless steel and rubber surfaces. The results suggest that UV-C can be used to reduce the biofilm formation and could be a promising alternative for controlling Alicyclobacillus spp. spores in industrialized orange juice.

Hesperidin-Loaded Solid Lipid Nanoparticles: Development and Physicochemical Properties Evaluation.

Although nanocarrier systems have been investigated to function as therapeutic delivery agents to specific sites of the body, the drug encapsulation method is not always well elucidated. In this work, solid lipid nanoparticles (SLN) composed by stearic acid or cetostearyl alcohol were prepared by a hot homogenization method using poly(vinyl alcohol) or polysorbate as surfactant and loaded with hesperidin, a bioflavonoid that possesses many pharmacological properties. The obtained SLN were characterized by several physicochemical techniques to identify interactions between the constituents and to evaluate the drug incorporation into the nanoparticles. According to scanning electron microscopy and dynamic light scattering the hesperidin-loaded and unloaded SLN have spherical shapes, sizes ranging from 300 to 600 nm, zeta potentials varying from -35 to -20 mV, polydispersity indexes between 0.240 and 0.445, and entrapment efficiencies higher than 88%. X-ray diffraction showed the hesperidin amorphization due to its encapsulation in SLN, and also showed crystallization degree and polymorphic modification of the lipids after the SLN preparation. FTIR, Raman and Photoacoustic spectroscopy revealed no chemical reactions between drug and lipids, however, these results indicated that the drug was incorporated differently into nanoparticles based on the SLN composition. The analysis showed that stearic acid-based SLN prepared with polysorbate were more efficient to enclosure the hesperidin while the glycosydic part of the hesperidin was not entrapped in the cetostearyl alcohol-based SLN; instead, the hesperidin remained on the SLN surface due to lipid crystallization. The physicochemical characterization allowed identifying different types of hesperidin incorporation into the SLN, which can interact in a varied manner as targeted drug delivery systems.

Quantitative assessment of radiation force effect at the dielectric air-liquid interface.

We induce nanometer-scale surface deformation by exploiting momentum conservation of the interaction between laser light and dielectric liquids. The effect of radiation force at the air-liquid interface is quantitatively assessed for fluids with different density, viscosity and surface tension. The imparted pressure on the liquids by continuous or pulsed laser light excitation is fully described by the Helmholtz electromagnetic force density.

Application of Photoreactive Barium Titanate (BaTiO3) Beam Fanning to the Photothermal Mirror Technique: An Experimental Analysis.

An adaptive spatial filter is used as an optical novelty filter to detect photothermal mirror (PM) signals in high absorbing materials using continuous wave laser excitation. The optical novelty filter uses an optical beam-fanning limiter based on single domain barium titanate (BaTiO3), cut and poled 45° relative to the c-axis. The optical novelty filter approach relaxes the requirement for high sample surface smoothness because the effect aperture adapts to the surface, reducing the stationary background from the optical signal and provides a means of developing the photothermal mirror signal. Time-dependent probe laser phase shifts due to photothermal surface deformation pass through the optical novelty filter and are detected as an intensity increase over the stationary or "mundane" signal. Experimental studies are performed using four well-characterized metals using both the conventional photothermal mirror and optical novelty filter apparatuses in order to understand the complicated signal behavior. Signal behavior is analyzed in different excitation intervals using pseudo-chopped sample excitation with different duty cycles. Optical novelty filter signals show fast response for changes in the spatial beam profile followed by long relaxation time. Reasons for the optical novelty filter response are described.

Photodegradation in Micellar Aqueous Solutions of Erythrosin Esters Derivatives.

Strong light absorption and high levels of singlet oxygen production indicate erythrosin B as a viable candidate as a photosensitizer in photodynamic therapy or photodynamic inactivation of microorganisms. Under light irradiation, erythrosin B undergoes a photobleaching process that can decrease the production of singlet oxygen. In this paper, we use thermal lens spectroscopy to investigate photobleaching in micellar solutions of erythrosin ester derivatives: methyl, butyl, and decyl esters in low concentrations of non-ionic micellar aqueous solutions. Using a previously developed thermal lens model, it was possible to determine the photobleaching rate and fluorescence quantum efficiency for dye-micelle solutions. The results suggest that photobleaching is related to the intensity of the dye-micelle interaction and demonstrate that the thermal lens technique can be used as a sensitive tool for quantitative measurement of photochemical properties in very diluted solutions.