Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2007
Publication Date: 6/20/2007
Citation: Tomasula, P.M., Kozempel, M.F., Konstance, R.P., Gregg, D.A., Boettcher, S., Baxt, B., Rodriguez, L.L. 2007. Thermal inactivation of foot-and-mouth disease virus in milk using high-temperature short time pasteurization. Journal of Dairy Sci. 90:3202-3211. Interpretive Summary: Fluid milk is preserved by a process known as High Temperature Short Time (HTST) pasteurization. In this process, milk is rapidly heated to temperatures at or over 72C for at least 15 seconds to reduce the number of harmful bacteria in milk, if present, to a level that does not constitute a health hazard. This study was conducted to determine the effectiveness of pasteurization on the Foot-and-mouth disease virus (FMDV). FMDV is not harmful to humans, but is highly contagious to dairy cattle, and other cloven-footed animals. If the animal contracts the virus, it is shed into their milk. The raw milk is a source for spread of the disease at the farm; to animals fed milk and milk products; or from farm to farm. The experiments showed that pasteurization greatly reduces the risk of transmission of FMDV by milk.
Technical Abstract: Previous studies of laboratory simulation of high temperature short time pasteurization (HTST) to eliminate foot-and-mouth disease virus (FMDV) in milk have shown that the virus is not completely inactivated at the legal pasteurization minimum (71.7 deg C/15 sec) but is inactivated in flow apparatus at 148 deg C with holding times of 2 to 3 s. It was the intent of this study to determine if HTST pasteurization conducted in a continuous flow pasteurizer enhances FMDV inactivation in milk. Cows were inoculated in the mammary gland with the field strain of FMDV (01/UK). Infected raw whole and 2% milks were then pasteurized using an Armfield pilot scale continuous flow HTST equipped with a plate and frame heat exchanger and a holding tube. The milk samples, containing FMDV at levels up to 104 pfu/mL, were pasteurized at temperatures ranging from 72 deg C to 95 deg C at holding times of either 18.6 or 36 s. Pasteurization decreased virus infectivity by 4 log10 to undetectable levels in tissue culture. However, residual infectivity was still detectable for selected pasteurized milk samples as shown by intramuscular and intradermal inoculation of milk into naïve steers. We conclude that although pasteurization does not completely inactivate viral infectivity in milk, possibly because a fraction of the virus is protected by milk fat, it greatly reduces the risk of natural transmission of FMDV by milk.