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Evaluate bactericidal Ti[O.sub.2] nanoparticles for food safety applications.

Titanium dioxide (Ti[O.sub.2]) is a promising photocatalyst for use in food safety applications. However, the selection criteria for attaining maximum biocidal activity still have to be determined.

The main objective of scientists at the University of Georgia was to develop a systematic testing protocol for selecting bactericidal Ti[O.sub.2] nanoparticles. Nanoscale Ti[O.sub.2] that is manufactured for specific applications is approximately by a factor of 100 finer than Ti[O.sub.2] pigments. The production volume of nanoscale Ti[O.sub.2] amounts to less than 1% that of Ti[O.sub.2] pigments.

A photocatalyst accelerates a photoreaction in the presence of a catalyst. The researchers tested the photocatalytic bactericidal activity of Ti[O.sub.2] nanoparticles at 1 mg per ml concentrations against E. coli O157:H7. They also determined the effects that: three different sources of commercial nanoparticles; three bacterial cell wash conditions; different mixture volumes--10, 20, and 30 ml; and different intensities of ultraviolet A light--1 and 2 milliwatts (mW) per [cm.sup.2] per second--would have on bactericidal activity.

Using magnetic stirrers, the scientists conducted the tests in a glass petri dish containing the reaction mixtures. This dish was illuminated with ultraviolet A light. The log reduction that occurred after three hours of treatment was determined in triplicate.

The researchers found one sample, T3, to be the most effective among the three tested Ti[O.sub.2] samples. This may be attributable to the increased generation of reactive oxygen species caused by the mixed anatase-rutile phase of the nanoparticles.

As expected, increasing the number of cell washes from one to three also increased the overall log reduction, from 2.91 to 4.57. Increasing the intensity of ultraviolet light increased the overall log reduction, up to 4.22. The volume of the different reaction mixtures showed a variable trend. The effect of volume was not significant on the least effective sample, while other samples were more effective at a lower volume of 10 ml.

Researchers were able to identify the best testing protocol for evaluating the bactericidal efficacy of Ti[O.sub.2] nanoparticles using a single wash of bacterial cells with a reaction mixture volume of 20 ml and an ultraviolet A light intensity of 2 mW per [cm.sup.2] per second.

Further information. Yen-Con Hung, Department of Food Science and Technology, University of Georgia, 1109 Experiment St., Griffin, GA 30223; phone: 770-412-4739; email:

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Author:Hung, Yen-Con
Publication:Emerging Food R&D Report
Date:Jul 1, 2016
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