In this brief guide, we are going to answer the question “4 ways to preserve food” and discuss 4 methods of food preservation along with the benefits and implications of each method.
4 ways to preserve food
The global human population is expected to reach 9.7 billion people by the year 2050. As the human population continues to grow, we face increasing challenges to ensure that people will have access to safe, nutritious, and healthy food. By the year 2050, food production will need to increase by more than 50% of 2012 production levels to meet demand (1).
4 common ways to preserve food are:
Preserving food by freezing
Freezing is the most widely used method of food preservation since it is quick, efficient and can be done at home by anyone with a freezer. Freezing preserves food for about 3 to 12 months. Freezing is especially used for fruits, vegetables and meat products where the original taste needs to be preserved. Both raw and cooked food can be frozen.
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. The formation of ice crystals during freezing will rupture the cell walls of fruits and vegetables. This results in frozen fruits and vegetables becoming soft and mushy when they are thawed. Freezing may also cause physico-chemical changes, such as loss of water-binding capacity, resulting in drip loss; protein changes, leading to toughening or dryness; and loss of turgor. Many of these changes increase with increasing water-phase (2).
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 B and C.
The freezer temperature must be maintained at -18 °C or slightly below for optimum shelf-life.
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. Dried foods should be stored in cool, dry, dark areas. Recommended storage times for dried foods range from 4 months to 1 year. Because food quality is affected by heat, the storage temperature helps determine the length of storage; the higher the temperature, the shorter the storage time. Most dried fruits can be stored for 1 year at 60ºF, 6 months at 80ºF. Vegetables have about half the shelf-life of fruits (4).and can be stored for up to 5 years under the correct storage conditions.
Food has been dehydrated by natural 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. Fatty foods are prone to develop rancidity at very low moisture content (less than monolayer moisture). Lipid oxidation is responsible for rancidity, development of off favors, and the loss of fat-soluble vitamins and pigments in many foods, especially in dehydrated foods (3).
Some commonly dehydrated food includes bananas, tomatoes, mangoes, zucchini and herbs such as parsley and oregano.
The most efficient way to dehydrate food is to use a food dehydrator.
Dehydrated food must be stored in an airtight container, in a cool, dry place. Dehydrated food can also be refrigerated or frozen to extend the shelf-life.
Disadvantages of dehydrating include the long time taken for dehydration (about 12 hours using a food dehydrator or several days using sun-drying) and the loss of nutrients during heating.
Preserving food by pickling
Ingredients used for producing pickled products include salt, vinegar (acetic acid), spices, sugar, and water. Pickled fruits and vegetables are made by immersing raw materials in brine containing vinegar (acetic acid) and salt, and then heat treated. Spices and sugar are used as additional ingredients to improve flavor. Therefore, salt, acetic acid, and heat are considered as major factors for increasing the microbial safety of pickled products (5).
Pickling is a method of preserving food by immersing in a solution of acidic brine or vinegar.
Pickling adds a distinct flavour 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.
There are 2 ways to pickle food.
- Anaerobic fermentation in a brine solution, resulting in the production of lactic acid.
- Marinating and storing in a solution of acetic acid (vinegar).
Spices such as cinnamon, cloves and garlic are added during pickling to enhance the flavour. These spices also have an antimicrobial effect that helps to extend the shelf-life of pickles.
Foods that can be preserved by pickling include fruits, vegetables, eggs, meat and fish.
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 (6). Pickling also reduces the nutrient content of food.
Preserving food by canning
In the air, water, and soil and on food and equipment are microscopic organisms that cause food to spoil that must be destroyed by heat and must be brought to a sufficiently high temperature and held at that temperature a sufficiently long time to destroy the bacteria and other organisms that cause spoilage. Processing is the term applied to this heating of food that brings about sterilization or conditions that prevent the growth of organisms (7).
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 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.
There are 3 ways of canning food.
- Water bath canning: Fruits, jams and acidified food such as pickles can be canned using the water bath canning method. A water bath for canning can be made at home using a large pot and racks to hold the canning jars.
- Pressure canning: Low acid meat and vegetables must be canned using a pressure canner. Using a water bath will not destroy certain microorganisms such as botulism spores which are present in low acid foods.
- Atmospheric steam canning: This is a relatively new canning method and is used to can high acid food products.
More about canning techniques can be found here.
Some commonly canned fruits and vegetables include beans, tomatoes, mushrooms, pineapple and corn.
In this brief guide, we answered the question “4 ways to preserve food”. We discussed 4 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.
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- Andress, E. Drying Packaging and Storing Dried Foods. University of Georgia.
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- Abou-Zaid, F. Pickled cucumber production for hypertension patients. Int j adv res, 2015, 3, 1490-1497.
- Naczk, Marian, and Alekseevna Svetlana Artyukhova. Canning. Seafood: Resources, Nutritional Composition, and Preservation. CRC Press, 2020. 181-198.