Hydrophobically-modified silica aerogels: Novel food-contact surfaces with bacterial anti-adhesion properties

• Methylated silica aerogel could strongly inhibit bacterial adhesion.
• Attachment of Salmonella and Listeria on aerogel was >99.9% less than that on glass.
• Bacterial anti-adhesion of aerogel was ascribed to its hydrophobic nanopores.
• Methylated silica aerogel exhibited excellent thermal insulation property.

In the context of food safety, contamination of food-contact surfaces with pathogenic bacteria is a global concern. This work investigates the potential of hydrophobically-modified, silica aerogel as a bacterial anti-adhesion food-contact surface. The bacterial anti-adhesion efficacies of hydrophobic silica aerogel, hydrophilic silica (negative control), and hydrophobic silica (positive control) were evaluated using dip inoculation with Salmonella Typhimurium LT2 and Listeria innocua NADC 2841 at 8.8 to 9.1 log CFU/mL. After rinsing, cells on these surfaces were enumerated by conventional plating as well as direct counting via scanning electron microscopy (SEM). Compared with the negative control, the positive control and silica aerogel led to a reduced number of salmonellae by 1.2 ± 0.1 log units (93.23 ± 0.91%) and by 3.1 ± 0.1 log units (99.93 ± 0.01%), respectively via plate counting (p < 0.05). The log reductions in the number of L. innocua were 1.3 ± 0.0 (94.82 ± 0.21%) and 3.0 ± 0.0 (99.91 ± 0.01%) for the positive control and silica aerogel, respectively via plate counting (p < 0.05). Additional bacterial proliferation studies revealed that bacterial anti-adhesion properties, not antibacterial effects, were responsible for the observed reductions. Overall, bacterial anti-adhesion property as well as other distinctive properties such as superior thermal insulation and ultra-lightweight make hydrophobically-modified silica aerogel an attractive candidate as a novel food-contact surface.