According to HowStuffWorks, food preservation slows down the activity of disease-causing bacteria or kills bacteria in food altogether. Preserving food keeps it from spoiling too quickly, allowing it to last for weeks or even months longer than it does normally.
Popular methods of preserving food include freezing, canning, dehydrating and salting. These preservation methods inhibit the growth of bacteria by either eliminating moisture from foods or removing the oxygen that harmful bacteria needs to survive and thrive, according to About.com's Bethany Moncel. Without these preservation methods, food grows bacteria, fungus and yeast, and it starts to degrade.
Another popular method of preserving food is fermenting, notes Moncel. This method is not only used to make food last longer, but it also gives food a unique flavor. Fermentation is a controlled preservation process in which the food spoils slightly, but the type of microorganisms produced help keep harmful bacteria from thriving. Examples of fermented foods include beer, yogurt, vinegar, cheese, wine and ketchup.
Eating fermented foods can also benefit health. According to the Mayo Clinic, dairy products, vinegar, and sauerkraut produce beneficial bacteria during fermentation, and this bacteria can increase energy absorption and cause the amount of healthy bacteria in the digestive tract to multiply.