Ensuring the safety of dehydrated milk products is of paramount importance, especially when it comes to the potential threat posed by thermoresistant spores of thermophilic bacteria. This blog post unveils the meticulous procedure defined by ISO 27265:2009 for enumerating these spores, emphasizing the critical role it plays in preventing poisoning agents and protecting infants from severe infections.
The Significance of Thermoresistant Spores
Microorganisms capable of forming spores adapt to survive UHT processes, presenting a risk of contamination in dehydrated milk products. Spores can endure temperatures up to 140oC, particularly within the range of 90oC to 121oC. Once these products return to room temperature, spores may develop into full microorganisms like Clostridium or Cronobacter. The latter, while infrequent, can lead to severe and even lethal infections such as septicemia or meningitis, making their presence particularly dangerous in dried milk for babies.
Procedure According to ISO27265:2009:
Initiate the process by preparing the primary dilution according to ISO 6887-5.
2. Sample Heat Treatment:
After diluting the sample 1:10, transfer 10 mL to different tubes and subject them to a boiling water bath. Record crucial temperature points:
Sample reaching 100oC (close steam vent).
Pilot reaching 105.5oC (max. 6').
Maintain a constant temperature of 106oC for 30' since reaching the second step.
Turn off the heat source and, when the pilot tube is below 100oC, release pressure and transfer the rack to a bath at 15 - 25oC.
3. Inoculation and Incubation:
Transfer 1 mL of the primary dilution, secondary dilution, and pilot to 3 petri dishes each with BCP Count Skim Milk Agar with 0.2% mass starch. Pour 15 mL of media into each dish, mix thoroughly, and cultivate at 55oC for 48 hours.
4. Counting Colonies:
Perform colony counting under subdued light to assess the concentration of thermoresistant spores.
This comprehensive enumeration process serves as a crucial step in ensuring the safety of dehydrated milk products, particularly those destined for infants. By adhering to ISO 27265:2009, producers contribute significantly to preventing potential health hazards, guaranteeing the well-being of the most vulnerable consumers.