Page "Vacuum flask cooking" Paragraph 17

If a large part of the cooking time is spent at temperatures lower than 60 ° C ( as when the contents of the cooker are slowly cooling over a long period ), a danger of food poisoning due to bacterial infection, or toxins produced by multiplying bacteria, arises.

It is essential to heat food sufficiently at the outset of vacuum cooking.

60 ° C throughout the dish for 10 minutes is sufficient to kill most pathogens of interest, effectively pasteurizing the dish.

The best practice is to bring briefly to a rolling boil then put the pot in the flask.

This keeps it hottest longest.