Why can foods such as pineapples, pickles and tomatoes be treated with temperatures less than 100?

The reason why foods such as pineapples, pickles and tomatoes can be treated with temperatures less than 100 is because these foods are highly acidic (pH<4.6) which provides a hurdle to microorganims.
Low-acid foods have pH values higher than 4.6, while acid foods have a pH of 4.6 or lower. They include fruits, pickles, sauerkraut, jams, jellies, marmalades, and fruit butters.

Predator instincts is what causes it