Purpose: The potential of 405 nm light to nonthermally inactivate TV coating the surface of blueberries was evaluated. The potential of compounds, which enhance singlet oxygen production to promote 405 nm inactivation was also evaluated.
Methods: Blueberries were immersed in TV (approximately 106/pfu ml), then air dried for one hour. For enhancer experiments, 0.1% w/v rose bengal or riboflavin was added to virus suspensions prior to contamination of blueberries. Berries were, subsequently, treated with 4.2mW/cm2 405 nm light for 5 to 30 minutes, rotating blueberries with forceps every one to two minutes to ensure exposure of all surfaces to 405 nm 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°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. It was noted that the addition of riboflavin and rose bengal, in the absence of the 405 nm light treatment, produced some inactivation. Average untreated reductions for riboflavin and rose bengal were -0.13 and -0.66, respectively.
Significance: Results indicate that 405 nm light may have some potential to inactivate viruses, if singlet oxygen enhancers are present.