This is true. The toxins left behind by bacteria or fungi can be worse than ingesting a live culture. And they don't break down by cooking at normal temperature

This is true. The toxins left behind by bacteria or fungi can be worse than ingesting a live culture. And they don't break down by cooking at normal temperatures. I think the only reason 5-year-old industrial mayo is ok is the preservatives. Fresh mayo can kill you after 24 hours unrefrigerated, whether you cook it later or not. Source: Worked in restaurants.