Inactivation of hepatitis E virus and murine norovirus during smoking treatments alone and an industrial warm smoking with additional heat treatment of pork sausages

Pork sausages are an important source of zoonotic hepatitis E virus (HEV) infection in humans. However, little is known how HEV is inactivated during industrial treatments of sausages. We aimed to assess the effect of smoking treatments alone and an industrial warm smoking with additional heat treatment. We smoked medium samples containing either HEV or murine norovirus (MNV) under different conditions. We also treated similar medium samples and self-made sausages containing MNV with an industrial warm-smoking process (60°C pre-heating, 65°C drying, 70°C smoking, 76°C heat treatment, 72°C additional heat treatment). Cell culture with virus titration (TCID 50 /ml) was used to assess the results. We observed a significant reduction in MNV infectivity after 10-min high-intensity smoking in dish samples (3 log 10 reduction, p < 0.001) and after 3 h of mild-intensity smoking in tube samples (1 log 10 reduction, p = 0.013). However, due to cytotoxicity HEV samples in these circumstances could not be analysed. By the end of our warm-smoking process, both viruses were completely inactivated. Inactivation of MNV took longer time in the sausage (68 min, > 3.8 log 10 reduction) than in the medium (54 min, > 5.9 log 10 reduction) (p < 0.001). Low titre HEV was inactivated fastest (43 min, > 1.4 log 10 reduction) but proportionally slower than MNV (p < 0.001). Our results suggest that smoking alone can reduce MNV load in the medium and that the warm-smoking process used in this study can both reduce infectious HEV in the medium and inactivate MNV also in the sausage matrix. • High-intensity smoking for 10 min decreased MNV titre in medium in culture dishes. • Mild-intensity smoking for 3 h decreased MNV titres in medium in sample tubes. • MNV titre decreased slower in sausage matrix than in cell culture medium. • No HEV or MNV were detected at the end of industrial warm smoking/heat treatment.