①Dehydration preservation: bacterial growth needs water, when the water in the food less than fifteen percent can effectively inhibit the growth and reproduction of bacteria. So people often make fresh milk into milk powder, fresh vegetables into a thousand vegetables, fresh dates drying into a thousand dates, fresh meat into bacon, etc.: ② Salt pickling sugar: because the general growth of bacteria need a certain pH and osmotic pressure. Excessive low are not conducive to bacterial growth. Using this reasoning, you can fresh meat, fish, eggs, fruit, vegetables, pickled into salted meat, salted fish, salted eggs, salted vegetables and candied fruit.　　③ cooling preservation: - general germs in 20 ℃ ~ 40 ℃ can grow and reproduce, and 37 ℃ is the most suitable. Below 0 ℃ or frozen in the basic stop growth and reproduction. So save food as far as possible to reduce the temperature to below 20 ℃, of course, the lower the better. Refrigerated food is best to use cold storage or refrigerator: if there is no such conditions, you can use the basement, air raid shelters, chilling and other methods, but the placement time should not be too long.