Stability of severe acute respiratory syndrome coronavirus 2 in dairy products

Norouzbeigi, Sahar; Yekta, Reza; Vahid‐Dastjerdi, Leily; Keyvani, Hossein; Ranjbar, Mohammad Mehdi; Shadnoush, Mahdi; Khorshidian, Nasim; Yousefi, Mojtaba; Sohrabvandi, Sara; Mortazavian, Amir M.

The present investigation was performed to determine the stability of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) under several industrial processing situations in dairies, including pasteurization, freezing, and storage in acidic conditions. Ten treatments were selected, including high‐temperature short‐time (HTST)‐pasteurized low‐fat milk, low‐temperature long‐time‐pasteurized low‐fat milk, extended shelf life (ESL)‐pasteurized low‐fat milk, HTST‐pasteurized full‐fat milk, LTLT‐pasteurized full‐fat milk, ESL‐pasteurized full‐fat milk, pasteurized cream, ice cream frozen and stored at −20 or −80°C, and Doogh (as a fermented milk drink with initial pH < 3.5) refrigerated for 28 days. The viral particles were quantified by RT‐PCR methodology. Besides, the virus infectivity was assessed through fifty‐percent tissue culture infective dose (TCID(50)) assay. These products were seeded with a viral load of 5.65 log TCID(50)/mL as a simulated cross‐contamination condition. Pasteurization techniques were sufficient for complete inactivation of the SARS‐CoV‐2 in the most dairy products, and 1.85 log TCID(50)/mL virus reduction in full‐fat milk (fat content = 3.22%). Freezing (either −20°C or −80°C) did not result in a virally safe product within 60 days of storage. Storage at high acidic conditions (initial pH < 3.5) completely hampered the viral load at the end of 28 days of refrigerated storage. This research represents an important practical achievement that the routine HTST pasteurization in dairies was inadequate to completely inactivate the viral load in full‐fat milk, probably due to the protective effect of fat content. Furthermore, freezing retain the virus infectivity in food products, and therefore, relevant contaminated foods may act as carriers for SARS‐CoV‐2.