Answer:
There are many different bacterium. The method is to avoid them, and to retard their growth. Heat does not kill all bacterium. Some bacterium require a lack of oxygen (anaerobic), and other require oxygen (aerobic. Botulism poisoning comes from the clostridium botulinin. Clostridim Botulinin is an anaerobic bacterium. Freezing the bacterium will only preserve it. Exposure to air will kill it.
People love garlic. So too does the bacterium. Do not store garlic under oil or water. Keep it exposed to air and sunlight. Some bacterium will grow in any environment. Salmonella typhi can not be controlled by O2. It causes typhoid fever.