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Pasteurization units calculator1/16/2024 However, residual infectivity was still detectable for selected pasteurized milk samples, as shown by intramuscular and intradermal inoculation of milk into naïve steers. Pasteurization decreased virus infectivity by 4 log10 to undetectable levels in tissue culture. The milk samples, containing FMDV at levels of up to 10(4) plaque-forming units/mL, were pasteurized at temperatures ranging from 72 to 95 degrees C at holding times of either 18.6 or 36 s. Infected raw whole milk and 2% milk were then pasteurized using an Arm-field pilot-scale, continuous-flow HTST pasteurizer equipped with a plate-and-frame heat exchanger and a holding tube. Cows were inoculated in the mammary gland with the field strain of FMDV (01/UK). It was the intent of this study to determine whether HTST pasteurization conducted in a continuous-flow pasteurizer that simulates commercial operation would enhance FMDV inactivation in milk. 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 degrees C/15 s) but is inactivated in a flow apparatus at 148 degrees C with holding times of 2 to 3 s. Tomasula, P M Kozempel, M F Konstance, R P Gregg, D Boettcher, S Baxt, B Rodriguez, L L Thermal inactivation of foot-and-mouth disease virus in milk using high-temperature, short- time pasteurization. ![]() This study demonstrates that continuous laboratory and pilot-scale pasteurizers may be used to study inactivation of microorganisms only if the flow conditions in the holding tube are established for comparison with commercial HTST systems. The long hold section was 91% plug and 9% back mixed for whole milk at 72 degrees C. The RTD study indicates that the short hold section was 45% back mixed and 55% plug flow for whole milk at 72 degrees C. Using brine milk as tracer, the FMP time for the short holding section was 18.6 s and for the long holding section was 36 s at 72 degrees C, compared with the nominal times of 21.5 and 52.2 s, respectively. Tracer studies were used to determine FMP times and RTD data to establish flow characteristics. The pasteurizer was equipped with nominal 21.5- and 52.2-s hold tubes, and flow capacity was variable from 0 to 20 L/h. The overall dimensions of the plate in the pasteurizer were 75 x 115 mm, with a thickness of 0.5 mm and effective diameter of 3.0 mm. ![]() ![]() In this study, we present a method for determining the fastest moving particle (FMP) and residence time distribution (RTD) in a pilot-scale high temperature, short time (HTST) pasteurizer to ensure that laboratory or pilot-scale HTST apparatus meets the Pasteurized Milk Ordinance standards for pasteurization of milk and can be used for obtaining thermal inactivation data. Flow characteristics of a pilot-scale high temperature, short time pasteurizer.
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