Sterile food has no bacteria. Bacteria is found in food if it hasn’t been sterilized.

Different ways to preserve foods are:

1. Refrigeration and freezing. These are the most popular ways. Refrigeration slows bacteria to a crawl to prevent spoiling. Freezing stops bacteria action completely. It can be used on all foods with little effect to the taste, except for fruit.

2. Canning. This has been around since 1825. You boil food to kill the bacteria and then seal the container (that can be boiled). You seal it before or while the food is boiling. This will prevent any new bacteria from getting in. Once the can is opened, bacteria can get in and spoil it . That is why you refrigerate it after it has been opened. Canning will usually change the taste and texture of the food. Food will also lose nutrition through this process.

3. Dehydration. Most bacteria will die when dehydrated. Drying will change the taste and texture of the food. Often it will change it altogether. An example of this would be a raisin.

4. Freeze drying. This is different than dehydration. Food is frozen and put in a strong vacuum. The water turns from ice to vapor. The most common use is for instant coffee.

   FREEZE DRYING EXPERIMENT It will take about a week, but give it a try. You need: perforated tray (cake cooling rack ok), something to freeze dry (apple, potato or carrot). Cut it as thin as you can. The thinner you cut it, the quicker it will dehydrate. Arrange it on the rack and put it in the freezer. Do this quickly before it discolors. Check it in ½ hour. Check it over the next week. The water will go directly from the solid water to water vapor, never going through the liquid state. Freeze drying will be complete in about a week. To test it, take one slice out. It will turn black almost immediately if not completely dry. You can reconstitute freeze dried foods by putting them in a bowl with a little boiling water. Taste will stay about the same.

   5. Salting. This is an ancient way of preservation, especially of meat. The salt takes moisture out, so bacteria cannot grow. It is better to salt in cold weather. If it is hot, the meat will spoil quicker, and the salt would not have had time to work.

   This method was replaced with refrigeration and freezing. The exception is when using it for taste in salt-cured meat: ham, beef and pastrami. For this method, they soak the meat in 10% salt water for several weeks.

   6. Pickling. This was used for meat, fruit and vegetables in the past. Today, it is just for pickles. They use salt, acid and vinegar. Acetic acid also stops bacterial growth. For pickles you soak in 10% salt water brine for several days, rinse and store in vinegar. This can last for years.

   7. Pasteurizing. When you boil food, you kill bacteria, making it sterile. You also change the taste and nutritional value. Pasteurizing is used for liquids. This will kill some bacteria and stop some enzymes through heating. Milk is the most commonly known product that is pasteurized. Juice and ice-cream are pasteurized also. It would take ½ hour at 145 degrees or 15 seconds at 163 degrees to pasteurize milk.

   8. Fermentation. You need yeast for this method. This will produce alcohol which will kill bacteria

   9. Carbonation. This method takes carbon dioxide gas that has been dissolved under pressure. By taking out the oxygen, bacteria stops growing. Carbonated drinks have a natural preservative.

   10. Cheese-making uses bacteria and enzymes, naturally forming acids to solidify milk proteins and fat and preserve them. Once turned into cheese, it can be preserved for years. Salt and acid are the main reasons why they can be preserved for so long.

   11. Chemical preservation. There are 4 kinds used:

   1. benzoates
   2. nitrates
   3. sulfites
   4. sorbic acid

   They all either slow down or kill bacteria.

   12.Irradiation. This kills bacteria without changing the food. You need to seal food in plastic, then radiate it. It will become sterile and can be stored on the shelf. It doesn’t change the taste. This could prevent food poisoning, but it is not popular because of the radiation. People don’t like that idea.

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What effect did the spices Kate used in her peaches have on the preservation of the fruit?

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