SPECIAL ISSUE ARTICLE
Evaluation of 405-nm monochromatic light for inactivation
of Tulane virus on blueberry surfaces
, R.E. Perez-Perez
, G. Boyd
, J. Sites
and B.A. Niemira
1 Food Safety and Intervention Technologies Research Unit, USDA, ARS, ERRC, Delaware State University, Dover, DE, USA
2 Food Safety and Intervention Technologies Research Unit, USDA, ARS, ERRC, Wyndmoor, PA, USA
405-nm light, blueberries, riboﬂavin, rose
bengal, singlet oxygen, virus.
David Kingsley, Food Safety and Intervention
Technologies Research Unit, USDA, ARS,
ERRC, Delaware State University, Dover, DE,
Mention of trade names or commercial
products in this publication is solely for the
purpose of providing speciﬁc information and
does not imply recommendation or
endorsement by the U.S. Department of
Agriculture (USDA). The USDA is an equal
opportunity provider and employer.
2017/1970: received 19 July 2017, revised 2
October 2017 and accepted 25 October 2017
Aim: The study aim was to evaluate the potential of 405-nm light as a virus
intervention for blueberries.
Methods and Results: Tulane virus (TV)-inoculated blueberries were treated
of 405-nm light for 5–30 min. To mitigate thermal heating
due to the intense light, a dry ice-chilled, nitrogen-based cooling system was
utilized. Blueberries were rotated to ensure exposure of all surfaces to 405-nm
light. Five-, 15- and 30-min treatments resulted in little or no inactivation of
TV on blueberries (average log reductions of À0Á18; À0Á02; and +0Á06
respectively). Since 405-nm light’s inactivation mechanism may involve singlet
oxygen, two singlet oxygen enhancers, riboﬂavin and rose bengal, were used to
coat the blueberries prior to 405-nm light treatment. When 0Á1% riboﬂavin or
rose bengal was added, resulting in an average PFU reduction of À0Á51 and
À1Á01 logs respectively. However, it was noted that the addition of riboﬂavin
and rose bengal in the absence of 405-nm light treatment produced some
inactivation. Average untreated log reductions for riboﬂavin and rose bengal
were À0Á13 and À0Á66 respectively. Also, 60–30-s 405-nm light pulses with 2-
min ambient cooling periods without the dry ice nitrogen cooling system did
not inactivate TV, suggesting that oxygen limitation by the nitrogen CO
mixture was not the cause of limited inactivation.
Conclusions: Overall results indicate that 405-nm light has some potential to
inactivate viruses if singlet oxygen enhancers are present.
Signiﬁcance and Impact of the Study: The potential of visible monochromatic
violet/blue light (405 nm) as a nonthermal intervention for viruses on foods, such
as berries that are prone to norovirus contamination, had not been previously
evaluated. Use of food-grade singlet oxygen enhancer compounds in combination
with visible spectra light may offer a means to inactivate foodborne viruses.
Human norovirus (HuNoV) is recognized as the leading
cause of gastroenteritis (Hal et al. 2013). This pathogen is
transmitted mainly through the faecal–oral route, by per-
son-to-person contact or contaminated food, irrigation
or drinking water and from contaminated surfaces
(Kingsley 2011). The infectious dose for HuNoV has been
estimated to be between 18–1000 particles (Teunis et al.
2008; Atmar et al. 2014), making HuNoV a highly conta-
gious virus. Fruits and vegetables that are not cooked
prior to consumption are potential sources of HuNoV,
(Kniel and Shearer 2009; Tavoschi et al. 2015). In vitro
propagation of HuNoV is currently very challenging
(Ettayebi et al. 2016), making assessment of viability and
inactivation of HuNoV problematic. Therefore, research
on nonthermal inactivation methods for HuNoV often
utilizes genetically related surrogates, such as murine nor-
ovirus and Tulane virus (TV; Farkas 2015).
Visible blue 405-nm light is one potentially promising
inactivation technology. The antimicrobial effect of visible
405-nm blue light is known to be effective against
Journal of Applied Microbiology 124, 1017–1022. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.
Journal of Applied Microbiology ISSN 1364-5072