Food preservation

Food preservation is the process of treating and handling food to stop or slow down spoilage. It  involves preventing the growth of bacteria, fungi (such as yeasts), or other micro-organisms , as well as retarding the oxidation of fats that cause rancidity, and thus increases the shelf life of food. Preservation is co-related to storage. Proper storing of food will help maintain food quality and safety. Employees who store food play an important role.

Food preservation in ancient times.

To survive ancient man had to harness nature. In frozen climates he froze seal meat on the ice. In tropical climates he dried foods in the sun. Other process including various types of cooking, such as roasting, smoking, steaming, fermenting, and preserving with salt were in practice.

In ancient times, the sun and wind would have naturally dried foods. Evidence shows that Middle East and oriental cultures actively dried foods in the hot sun as early as 12,000 B.C. The Romans were particularly fond of any dried fruit they could make.

In the early 1900s, natural draft dehydrators were created to dry fruits, vegetables and herbs in areas that did not have enough strong sunlight for drying. These early dehydrators were designed with fire pits on the bottom and exhaust vents at the top. As the fire heated the air, it was carried upwards creating the critical air flow and low humidity that is essential for dehydration.

Food Preservation Methods

You can preserve foods traditionally & industrially & inexpensively by using canning, freezing, or drying techniques. Some other industrial and curing methods for preservation are below.

1.  Drying is the process of dehydrating foods until there is not enough moisture to support microbial activity. It can be used with most foods, including fruits, vegetables, meats, seafood, grains, legumes, and nuts. There are several different techniques, some are relatively easy to do and require no special equipment. Vegetables and fruit are naturally dried by the sun and wind, but in the middle Ages, "still houses" were built in areas that did not have enough sunlight to dry things. A fire would be built inside the building to provide the heat to dry the various fruits, vegetables, and herbs.
2. Refrigeration and Freezing is also one of the most commonly used processes, both commercially and domestically, for preserving a very wide range of foods, including prepared foods that would not have required freezing in their unprepared state. This method preserves foods by slowing down the growth and reproduction of micro-organisms and the action of enzymes that cause food to rot.                         Perishable foods are foods that can spoil quickly if not properly stored. Examples include meat, dairy, fish, poultry, produce, and some baked items. Do not store perishable foods in the refrigerator door. Put them on the shelves in the main part of the refrigerator. Opening the refrigerator door can increase the temperature of foods stored in the door.                                                                                                   Foods frozen at peak quality will taste better than foods frozen near the end of their useful life, so quickly freeze items you don't plan to use in the next day or two. It is safe to freeze foods in their supermarket wrappings. Use these foods within a month or two. Many supermarket wrappings are air permeable. So, for longer storage, overwrap packages with airtight heavy-duty foil, plastic wrap, or freezer paper, or place packages inside a plastic bag.

3. Canning and bottling is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a shelf life typically ranging from one to five years, although under specific circumstances it can be much longer.

Canned goods include both those that are store-bought, and those that are home-canned. They should be kept at temperatures between 32 and 100 degrees Fahrenheit, and kept dry to prevent rusting of the aluminum parts of their containers. Low acid foods like corn, beans, meats and pastas are safe for two to five years, while high-acid foods like tomatoes, sauerkraut and those with vinegar bases should not be stored longer than 18 months.

Lack of quality control in the canning process may allow ingress of water or micro-organisms. Most such failures are rapidly detected as decomposition within the can causes gas production and the can will swell or burst. However, there have been examples of poor manufacture (underprocessing) and poor hygiene allowing contamination of canned food by the obligate anaerobe Clostridium botulinum, which produces an acute toxin within the food, leading to severe illness or death.

                        

           4.    Chemical preservation, in which substance are added in very low quantities (up                   to 0.2%) and which do not alter the organoleptic and physico-chemical properties                   of the foods at or only very little. Chemical food preservatives are applied to                           foods as direct additives during processing, or develop by themselves during                         processes such as fermentation. Certain preservatives have been used either                       accidentally or  intentionally for centuries, and include sodium chloride (common                   salt), sugar, acids, alcohols and components of smoke. In addition to                                     preservation, these compounds contribute to the quality and identity of the                             products, and are applied through processing procedures such as salting, curing,                   fermentation and smoking.

             

Chemical compound	comment
Benzoic acid, sodium benzoate	Used in acids foods like jams, salad dressing, pickle, juices carbonated drinks
Hydroxybenzoate & derivatives	Stable at broad pH range
Lactic acid	Against antimicrobial agents
Nitrites	Used in meat to prevent botulism toxin
Nitrates	In meats
Propionic acid & sodium propionate	Bakery items
Sulphur dioxide & sulphites	Common for fruit
Sorbic acid & sodium sorbate	Common in cheese, wine, baked goods