Evaluation of 405nm CW visible blue light as a means of inactivating Tulane Virus on Blueberries

Authors: Kingsley, David; Perez-Perez, Rafael; Boyd, Glenn; Sites, Joseph; Niemira, Brendan

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2017
Publication Date: 7/9/2017
Citation: Kingsley, D.H., Perez-Perez, R.E., Boyd, G., Sites, J.E., Niemira, B.A. 2017. Evaluation of 405nm CW visible blue light as a means of inactivating Tulane Virus on Blueberries.[Abstract]. International Association for Food Protection., Tampa, Florida., Volume 1, Page 1.

Interpretive Summary:

Technical Abstract: Introduction: Visible blue light (405nm) is effective against bacteria but its potential as a nonthermal intervention for viruses on foods, such as berries that are prone to norovirus contamination has not been evaluated. Tulane virus (TV) is now a common human norovirus surrogate that can be propagated in vitro. Riboflavin is a B vitamin and rose bengal is a food coloring agent. Both chemicals are generally recognized as safe (GRAS). Purpose: The potential of 405nm light to non-thermally inactivate TV coating the surface of blueberries was evaluated. The potential of compounds which enhance singlet oxygen production to promote 405 inactivation was also evaluated. Methods: Blueberries were immersed in TV (approximately 106/pfu ml), then air dried for 1 hr. For enhancer experiments, 0.1% w/v rose bengal or riboflavin was added to virus prior to contamination of blueberries. Berries were subsequently treated with 4.2mW/cm2 405nm light for 5 to 30 minutes, rotating blueberries with forceps every 1-2 minutes to ensure exposure of all surfaces to 405 light. To mitigate thermal heating due to the intense light, a dry ice-chilled nitorgen-based cooling system was utilized to ensure that temperatures remained below 35 degrees C at all times. Results: Five, 10, and 30 min treatments resulted in little or no inactivation of Tulane on blueberries (average log reductions of +0.18; +0.02; and -0.06 respectively). However more substantial inactivation was observed, with riboflavin resulting in an average reduction of - 0.51 logs and -1.01 for rose bengal. However it was noted that the addition of riboflavin and rose bengal in the absence of 405 light treatment produce some inactivation. Average untreated reductions for riboflavin and rose bengal were- 0.13 and -0.66 respectively. Significance: Results indicate that 405 light may have some potential to inactivate viruses if singlet oxygen enhancers are present.