Trisodium Phosphate for Foodborne Virus Reduction on Produce

Human noroviruses (NoVs) are recognized as the major cause of acute nonbacterial foodborne gastroenteritis outbreaks in both developed and developing countries. They are resistant to most chemical inactivation processes, and can survive in the environment for long periods. The aim of this research was to apply trisodium phosphate (TSP) on spiked produce (lettuce and peppers) for the reduction of foodborne NoV surrogates, feline calicivirus (FCV-F9), and murine norovirus (MNV-1). Washed and dried lettuce (3 × 3 cm²) and Jalapeno peppers (25-30 g/pepper) were spiked with FCV-F9 and MNV-1 at titers of ∼7 log₁₀ plaque forming unit (PFU)/mL or ∼5 log₁₀ PFU/mL and dried aseptically in a biosafety hood for 5 min. Samples were treated with 2% TSP, 5% TSP, 200 mg/L sodium hypochlorite, or water for 15 or 30 sec. Treatments were immediately neutralized with cell culture media containing 10% fetal bovine serum, and viruses were recovered and evaluated using standardized plaque assays. No significant differences between the two contact times on viral reduction was observed (p > 0.05). All three chemicals reduced FCV-F9 titers at ∼5 log₁₀ PFU/mL to undetectable levels, but MNV-1 at ∼5 log₁₀ PFU/mL was decreased by ∼2-3 log₁₀ PFU/mL with 200 mg/L sodium hypochlorite and 2% TSP, and to undetectable levels by 5% TSP. FCV-F9 at ∼7 log₁₀ PFU/mL was reduced by >5 log₁₀ PFU/mL with 2% TSP, in comparison to 200 mg/L sodium hypochlorite that showed ≤ 1.4 log₁₀ PFU/mL reduction. MNV-1 at ∼7 log₁₀ PFU/mL was decreased by ∼2-3.4 log₁₀ PFU/mL with 2% TSP; and by <1.3 log₁₀ PFU/mL with 200 mg/L sodium hypochlorite. FCV-F9 and MNV-1 at ∼7 log₁₀ PFU/mL were reduced to undetectable levels by 5% TSP. Treatments by 5% TSP for 30 sec did not result in any statistically significant color changes of the tested produce. TSP at 5% appears suitable as an alternative treatment to chlorine washes for NoV reduction on produce, without any noticeable visual quality changes.