Use of polydimethylsiloxane topomimetic artificial blueberry, strawberry, and raspberry surfaces for the study of foodborne virus recovery and inactivation in berries

Foodborne viruses have caused large-scale outbreaks in fresh and frozen berries, such as strawberries, blueberries, and raspberries. Studies have previously evaluated the use of non-thermal technologies (including chemical sanitizers) to inactivate foodborne viruses on the surface of soft berries with varying results. In this study, we investigate a novel model system for utility in characterizing virus attachment and removal, as well as sanitizer inactivation on the surface of berries. A casting method using polydimethylsiloxane (PDMS) was used to create topomimetic artificial surfaces (“replicasts”) of strawberries, blueberries, and raspberries to elucidate the impact of berry surface structures (topography) on virus adhesion and inactivation. A human norovirus surrogate, Tulane virus (TV), was inoculated (2 × 10 5 log 10 PFU) on the surface of fresh and replicast berries, and viral recovery levels were compared. Overall, the type of berry impacted viral recovery, with 5.11 log 10 PFU recovered from blueberries, 5.04 log 10 PFU recovered from strawberries, and 5.66 log 10 PFU recovered from raspberries. Surface inoculation of blueberry, strawberry, and raspberry replicasts with TV led to comparable recovery levels of virus as observed in fresh berries, with 4.80, 4.93, and 5.17 log 10 PFU recovered, respectively, with a two-step recovery procedure. Sodium hypochlorite (200 ppm) led to less than a one log 10 PFU reduction in viral titer in all three types of fresh berries. However, the same sanitizer treatment and two-step recovery procedure led to a 2.45 log 10 PFU reduction in blueberry replicasts, 2.24 log 10 PFU reduction in strawberry replicasts, and 1.59 log 10 PFU reduction in raspberry replicasts. Sodium hypochlorite (50 ppm) and peracetic acid (20 or 80 ppm) had limited efficacy in inactivating viruses inoculated to fresh berry or berry replicast surfaces. However, viral reductions were greater in replicasts compared to fresh berries when observed. These data indicate that while berry replicasts may have utility in modeling surface adhesion of viruses to berries and in viral recovery studies, they are not suitable for studies of viral inactivation by chemical sanitizers.