How We Preserve Food: A Review of Current and New Food Preservation Strategies

A new review highlights different methods of food spoilage and current strategies used around the world for food preservation and processing.

Food preservation, defined as the processes and techniques used to prevent food spoilage, allows for an increased shelf life of food while retaining the original nutritional value, color, texture and flavor of the food. Conventional food preservation techniques include drying, freezing, cooling, pasteurization and chemical preservation, while new technologies currently being explored include irradiation and high pressure technology. The food processing industry is worth nearly $7 trillion and is expected to continuously increase with ongoing globalization and industrialization. A recent study by Amit and colleagues, published in Agriculture and food securitysummarizes the different methods of food spoilage, as well as the mechanisms and techniques currently used in food preservation.

Mechanisms of food spoilage

Food spoilage can occur due to physical, microbial or chemical mechanisms, resulting in unpleasant food conditions and reduced edibility. Physical spoilage is a consequence of changes in food moisture content, temperature, crystal growth and crystallization. Suboptimal temperature conditions, for example, can lead to poor ripening of fruits and vegetables. Additionally, crystal growth can occur due to slow freezing or multiple freezing events of the product, and therefore negatively affect the quality of the product itself by inducing damage at the cellular level. Collectively, the correct ripening and storage temperature, as well as optimum moisture content are essential to prevent the physical spoilage of food.

Food spoilage can also occur due to the action of microorganisms, including moulds, yeasts and bacteria. Microbial spoilage can be avoided or reduced by optimizing storage temperature, reducing water activity, lowering pH, adding preservatives and using proper packaging techniques. In contrast, chemical spoilage of food involves chemical or biochemical reactions that lead to bad smell and taste of food.

The oxidation of amino acids and lipids (called rancidification), for example, in the presence of oxygen, can lead to discoloration, unpleasant flavor and the formation of toxic substances. Proteolysis, the chemical breakdown of proteins, can lead to peptide byproducts that often taste bitter, sweet, or off-putting. Putrefaction is a series of chemical reactions that can cause food to smell bad. Other examples of chemical spoilage include the Malliard reaction, which results in blackening and browning of foods, and hydrolytic rancidity, which results in bad smelling and bad tasting foods.

Food preservation and processing methods

It is important to understand the different mechanisms by which food can deteriorate, as it provides insight into the development of new food preservation and processing strategies. Physical food processing includes several different strategies, including drying, pasteurization, autoclaving, irradiation, high-pressure food preservation, and pulsed electric fields. Drying involves the removal of water from solid or liquid foods, through evaporation, to prevent food spoilage caused by microorganisms. Eliminating water also makes it easier to store, package and transport food by reducing the weight and bulk of the item. Pasteurization involves heating food to high temperatures to destroy spoilage-causing microorganisms and enzymes.

Although drying and pasteurization are widely used effective strategies, they are also associated with the loss of functional compounds and minerals. Other strategies to prevent food spoilage include freezing or chilling foods to reduce the rate of biochemical and microbiological changes. New strategies being actively investigated include irradiation, high pressure food preservation, and pulsed electric fields. Irradiation involves substances being dosed with ionizing radiation for the disinfestation and inactivation of spoilage organisms and foodborne pathogens. High pressure food preservation strategies use high pressures to kill microorganisms and inactivate spoilage, while pulsed electric fields involve the use of high voltage fields to destroy microorganisms.

Biological processing or fermentation uses microorganisms to prevent food spoilage. Not only does fermentation prevent spoilage, but it also improves the nutritional value and aids digestion of food. A more common method of food preservation is chemical processing, which uses preservatives and food additives to prevent spoilage and improve shelf life. The addition of food additives and preservatives to foods is carefully monitored and regulated as they can affect health. Preservatives work by inhibiting, delaying or stopping the growth of microorganisms, while food additives work to improve and maintain the nutritional value of foods, improve quality and facilitate processing.

New strategies must be continually explored

Proper food preservation and prevention of spoilage are important to increase shelf life, without compromising its nutritional value and taste. Understanding the mechanisms by which food can spoil (physical, chemical and microbial) is key to developing more effective food preservation strategies. Current strategies include physical, biological (fermentation) and chemical preservation strategies; however, newer strategies such as irradiation, high pressure food preservation, and pulsed electric fields need to be continually investigated.

Written by Haisam Shah, BSc

Reference: Amit, SK, Uddin, MM, Rahman, R., Islam, SR and Khan, MS (2017). A review of the mechanics and business aspects of food preservation and processing. Agriculture and food security, 6(1), 51.

Add to Flipboard magazine.