[Kinetics of the inactivation of Salmonella during thermal disinfection of liquid manure].

Technical processes for thermal liquid manure disinfection usually reach temperatures between 50 degrees C and 70 degrees C. The destruction of important infectious micro-organisms can be expected in this temperature range. The purpose of the investigations reported here was to study the thermal resistance of Salmonellae during heat treatment of liquid manure. Salmonella senftenberg 775W survived much longer than each of 12 other strains from 8 different Salmonella serovars. Resulting from a regression analysis kinetics of thermal death were determined for this strain and decimal reduction times were calculated in cases of an exponential die-off. D60-values ranged from 47 to 138 sec depending on the type of slurry used. Further investigations on the inactivation of Salmonella senftenberg 775W at 50 degrees C, 55 degrees C, 60 degrees C, and 65 degrees C were carried out and following D-values were obtained: D50 = 56.7 min, D55 = 11.5 min, D60 = 2.3 min, D65 = 0.47 min. The resulting ZD-value was 7.2 degrees C. Minimum requirements concerning temperature and heating time can be derived from the results of this study. The given recommendations may only be applied, if technical processes work without any functional deficiencies and thermal energy is evenly distributed in the heated slurry. Combinations of temperature and heating time should not fall below the following values: 50 degrees C/15 h, 55 degrees C/3 h, 60 degrees C/30 min, 65 degrees C/5 min.