5 ways to preserve food

In this brief guide, we are going to answer the question “5 ways to preserve food” and discuss 5 ways to preserve food along with the benefits and implications of each method.

What are 5 ways to preserve food

Preservation from microbial, chemical, and physical contamination, as well as enzymatic activity, is necessary for preserving and extending the shelf life (time a product can be stored without significant change in quality) of food (1).

5 common ways to preserve food are:

1. Freezing
2. Dehydrating
3. Pickling
4. Fermenting
5. Canning

Preserving food by freezing

Freezing is the most widely used method of food preservation since it can be done easily at home by anyone and food is preserved for 3 to 12 months. Freezing is especially used for fruits, vegetables, and meat products where the original taste and texture need to be preserved.

Freezing food reduces the enzyme activity in food that causes spoilage. Freezing also crystallizes the water in the food so microorganisms cannot use it for growth. Thus, bacteria are dormant, and consequently, there is no multiplication of pathogens. Rapid freezing by commercial freezing methods includes air blast tunnel freezing, plate freezing, and cryogenic freezing. Air blast procedures utilize  convection and cold air. Foods are placed either on racks that are subsequently wheeled into an insulated tunnel, or on a conveyor belt, where very cold air is blown over the food at a quick speed. In plate freezing, the packaged food is placed between metal plates, which make full contact with the product and conduct cold, so that all parts of the food are brought to 0° F (17.8 °C). Cryogenic freezing may involve either immersion or spraying the food product with liquid nitrogen, which has a boiling point of 320 °F (196 °C) and therefore freezes food more rapidly than other mechanical techniques (1).

Freezing itself does not significantly reduce the nutrient content of food. However blanching before freezing and defrosting will cause the loss of some nutrients, mainly water-soluble nutrients such as vitamin C.

Most cooked as well as raw meat, vegetables and fruits can be preserved by freezing. Dairy products such as butter and cheese are also preserved well by freezing.

Certain processed foods do not freeze well. These include cake frostings, mayonnaise, gelatin, and cream-based soups.

Preserving food by dehydrating

Dehydrating is one of the oldest methods of food preservation. Dehydrating works by removing the water from food, thereby reducing the growth of microbes that cause spoilage. Dehydrated food has a long shelf-life and can be stored for up to 5 years under the proper conditions.

Food has been dehydrated by natural air-drying and sun-drying for ages. Now there are electric dehydrators which can be used at homes. Food can also be dehydrated using an oven or a microwave.

Convection ovens are more suitable for dehydrating than conduction ovens. This is because they have better air-lower and lower temperatures. This prevents the food from burning. However, the best equipment for dehydrating is a food dehydrator. 

Other dehydration methods are drum drying, by which the product is dried on two heated stainless steel drums before it is scraped off (milk, juices, and purees may be dried in this manner); freeze drying, which freezes and subsequently vacuums the food to evaporate moisture in the process of sublimation (ice is converted to a vapor without passing through the liquid phase); examples include instant coffee, meats, and vegetables (1).

Herbs such as oregano, rosemary, and thyme are usually dehydrated. Most fruits and vegetables and low-fat meats can also be dehydrated.

Foods with a high-fat content do not dehydrate well. Examples are avocados, products with butter, and fatty meats.

Preserving food by pickling

Pickling is a method of preserving food by immersing in a solution of acidic brine or vinegar. Pickling is considered as a preservation method in which additives or preservatives are used to reduce the water available for microbial growth and enzymatic reactions of food or to change the environment to make it impossible for the development of microorganisms and therefore extend its shelf life. Vinegar is a natural additive that acidifies the food, thus it contains acetic acid (1).

Pickling adds a distinct flavor to food and pickles are used as side dishes and garnish in many cuisines.

Properly produced pickles can be stored for about a year. However, they must be refrigerated after being opened.

Some commonly pickled fruits and vegetables include mangoes, cucumber, limes, and radishes.

Pickles have a high content of sodium due to all the salt added for pickling. So eating large portions of pickles is not recommended. Pickles are also not recommended for people with hypertension and cardiovascular diseases due to the high sodium content. However, pickles made with vinegar were found to be beneficial to people with diabetes.

Preserving food by fermentation

Fermentation is easily confused with pickling. The difference is that there is no addition of an acidic medium such as acidic brine or vinegar during fermentation. During fermentation, the carbohydrates in food are broken down into acids or alcohols by bacteria and yeast. 

Ethanol fermentation is also known as alcoholic fermentation that converts sugars such as glucose, fructose, and sucrose into energy (ATP), ethanol and carbon dioxide as by-products. Lactic acid bacteria fermentation is done by using natural microflora or lactic acid bacterial cultures. Lactic acid fermentation produces acids, lowers the pH to a level at which most of the spoilage-causing microorganisms cannot grow, and, thus, the food is preserved (2).

Fermentation preserves most of the nutrients and also produces probiotics. Probiotics are beneficial bacteria that help in maintaining gut health and improving immunity.

Some commonly fermented foods include cheese, yogurt, sauerkraut, wine, beer, and sourdough bread.

Preserving food by canning

Canning preserves food by killing the microorganisms that cause spoilage. Canning can be done at home using the correct equipment and proper sterilization of jars but it is time-consuming and needs practice.

Nicolas Appert (1752–1841) is credited with the thermal process of canning (vacuum bottling technique), which was discovered in 1809 as a result of a need to feed Napoleon’s troops (1).

This preservation method involves severe heat treatment. Food is placed inside a cylinder, or body of a can, the lid is sealed in place, and the can is then heated in a large commercial pressure cooker known as a retort. Heating times and temperatures vary, although the heat treatment must be sufficient to sterilize the food. Temperatures in the range 241–250 °F (116–121 °C) are commonly used for canning (1).

Canned foods are shelf-stable for years and do not need refrigeration until they are opened. However, the heating process during canning reduces the nutrient content of food.

Canning is now done on a variety of commercial foods such as beans, corn, tomatoes, pineapple, etc. 

Popular homemade canned food include jams, marmalades, and sauces.

There are certain foods that must not be canned such as dairy products, very tender vegetables like broccoli and cauliflower, and dense purees. The low acidity and consistency of these foods make them unsuitable for canning.

There are 2 canning techniques. They are boiling water bath canning and pressure canning. Both these techniques can be done at home. Boiling water bath canning is used to preserve acidic food while pressure canning is used for non-acidic food. Pressure canning requires a pressure canner but water bath canning requires just a pot with boiling water.

Conclusion

In this brief guide, we answered the question “5 ways to preserve food”. We discussed 5 methods of food preservation and looked at the benefits and implications of each method.

If you have any questions or comments, please let us know.

References

1. Vaclavik, Vickie A., Elizabeth W. Christian, and Tad Campbell. Food preservation. Essentials of food science. Springer, Cham, 2021. 327-346. 
2. Mani, Arghya. Food Preservation by Fermentation and Fermented food products. Int J Acad Res Dev, 2018, 1, 51-57.