Spores in dairy – new insights in detection, enumeration and risk assessment

The performance of the ISO method for the ‘Enumeration of the Specially Thermoresistant Spores of Thermophilic Bacteria in Dried Milk’ (ISO/TS27265; 2009) was compared with a more practical method. Both were tested for predictability of spoilage of UHT treated reconstituted milk. The data show that heating for 30 min at 100 °C has the same predictive value as heating for 30 min at 106 °C, provided that specifications are increased 1 log10 and the use of TSA as a cultivation medium is recommended over PCMA. Predictability of spoilage using classical plating methods is furthermore discussed in relation to variation in spore heat resistance of spores commonly present in the dairy industry.