Food Preservation

Summary

Food preservation involves the application of scientific methods to prevent agricultural resources, whether eaten raw or further processed, from becoming contaminated or spoiling. Preservation ensures that people have sufficient supplies of food to survive. The availability of preserved foods makes it easier for people to migrate and settle in new areas. Explorers and military forces rely on preserved foods for nourishment. Preservation methods also enable perishable foods to be traded worldwide.

Definition and Basic Principles

Food preservation is the science of destroying or impeding the growth of harmful microorganisms, slowing oxidation, and controlling chemical reactions that cause foods to decay and become inedible. Food technologists and scientists realize that food will inevitably decay but that preservation strategies can extend its freshness. Food preservation professionals develop procedures and technologies to decrease spoilage, which contributes to the waste of 1.3 billion tons of the food produced globally each year, according to global research firm World Resources Institute in 2021. They improve packaging, which keeps out hazardous contaminants, and devise innovative storage and transportation modes to maintain food quality, facilitating the manufacture and distribution of more food varieties worldwide.

Preservation is essential to ensure a consistent and sufficient supply of safe food to nourish global populations. Manufacturing processes to protect foods from contaminants typically involve exposing them to temperature extremes, using chemicals, applying high pressures, placing foods in a vacuum, or passing them through radiation or diverse energy sources. Removing moisture and drying foods is basic to many food preservation methods. Food and beverage packaging uses protective films, including edible coatings, gases injected into or removed from food containers, and aseptic environments to package foods.

Critics of food preservation allege that many of the preservatives added to foods are dangerous and suggest that nonchemical alternatives be developed and employed. They also protest the use of irradiation and other controversial technologies that they believe may be carcinogenic or pose other health risks to consumers. The US Food and Drug Administration (FDA) responds to these criticisms by investigating potential threats involving food preservation and setting standards for those processes, such as establishing permitted irradiation dosages for various foods.

Background and History

Since ancient times, people have preserved surplus food to eat when fresh foods are not readily available. Early methods included drying or cooling foods and using easily obtainable preservatives such as honey, vinegar, alcohol, fats, sugar, and oils. Hanging foods to dry reduced their moisture content and minimized decay. Foods could be cooled in caves, snow, and streams. Standard preservation methods included salting, pickling, and fermenting. Many of these basic preservation strategies are incorporated into modern methods.

In the late eighteenth century, scientists became aware that microorganisms existed but did not know that microbes could cause food to spoil. By the early nineteenth century, confectioner Nicolas François Appert had devised a technique to preserve food in glass bottles, which served as the foundation for modern industrialized canning. Food preservation techniques improved as people learned how microorganisms made food spoil. In the mid-nineteenth century, French bacteriologist Louis Pasteur developed the pasteurization process, which uses heat to destroy microbes. This process, named after its inventor, became intrinsic to food preservation. In the 1850s, inventor Gail Borden Jr. used vacuum technology to remove air from containers to create condensed milk, which remained fresh for extended periods while shipping or in storage. In the 1880s, Gustavus F. Swift, founder of a meatpacking company, created refrigerated railroad cars to preserve meat being transported over long distances. In the 1920s, businessman and inventor Clarence Birdseye patented a process to flash-freeze foods.

As food preservation methods (some harmful) and patent medicines proliferated with little or no regulation, the US government enacted legislation to ensure the quality of foods and drugs. The Pure Food and Drug Act of 1906 allowed the federal government to inspect meat products and prohibited the “manufacture, sale, or transportation of adulterated or misbranded or poisonous or deleterious foods, drugs, medicines, and liquors.” The law's focus was on the accurate labeling of products. Although the FDA can trace its history to 1848, it began acting as a consumer protection agency after the passage of the 1906 Act. Many additional laws regarding food and drug safety followed.

How It Works

Maintaining the freshness of food as it goes from market to the table is accomplished through chemicals and other substances that act as preservatives, processes that prevent or delay food spoilage, and packaging that guards against the chemical reactions that initiate decay.

Preservatives. Food technologists use many preservatives, both chemical and natural. Natural food preservatives include antimicrobials that attack microorganisms. Enzymes that are effective antimicrobials include glucose oxidase, lactoperoxidase, and lysozymes. Antioxidants, such as vitamins C and E, butylated hydropxytoluene (BHT), and butylated hydroxyyanisole (BHA), block spoilage caused by oxidation. Other food preservation strategies involve adding acids to lower pH levels, which disrupts microbe activity and slows food deterioration.

Thermal Processes. Heat damages or destroys most microbes and harmful enzymes in foods. During pasteurization, heat penetrates food and eliminates most microorganisms. Food technologists adjust the duration and intensity of heat applied to foods depending on the process and the food and microbes or enzymes involved. Many manufacturers use high-temperature short-time (HTST) or ultra-high-temperature (UHT) methods. Foods are transported on conveyor belts into contained areas, where they are heated to the proper temperature and for the appropriate length of time. Automated canning and bottling systems produce thousands of cans or bottles per hour. The bottles or cans are filled with liquid or food and sealed with lids as they move along conveyor belts into heating chambers.

Aseptic food preservation processes differ from canning in that foods and containers are sterilized separately before packaging occurs. The foods are flash pasteurized and then cooled before being packaged and sealed in sterile containers in a sterile environment. This type of packaging, often used for soy milk and drink boxes, allows foods—with no added preservatives—to be kept for long periods without refrigeration. Other thermal food preservation methods include using energy from radio frequencies and microwaves to heat foods during manufacturing.

Nonthermal Processes. Because exposure to heat alters some foods' chemical properties, food technologists have devised alternative methods. Nonthermal techniques control microorganisms by applying electricity, radiation, pressure, or optics, individually or in combination. Some food manufacturers employ high-pressure processing (HPP), placing foods in chambers that can be pressurized at varying intensities. The ultra-high-pressure processing (UHP) technique pasteurizes foods, typically vegetables and fruits, by spraying them with powerful cold-water jets that remove most microbes.

Irradiation exposes foods to electron beams emitted by gamma rays, X-rays, or other radioactive sources producing ions for several seconds to an hour. The FDA and the US Department of Agriculture regulate irradiation dosages to disinfect specific foods. Other nonthermal food preservation methods include electronic pasteurization or the use of a pulsed electric field (PEF), pulsed magnetic field (PMF), or high intensities of pulsed light (PL) to inactivate microbes. Ultrasound preservation processes inactivate hazardous spores, enzymes, and microorganisms in foods.

Cooling and Freezing Processes. Reducing food temperatures is an effective way to slow biodeterioration because chilling foods alters the kinetic energy of microorganisms. In these processes, food is placed on conveyor belts and moved past chilled metal plates, coils holding refrigerants, compressors, and evaporators. Temperatures of 0 degrees Celsius (freezing point of water) or lower kill most microbes or impede their movement. The type of freezing machinery and chemicals used determines how long the freezing process takes; some methods instantly freeze foods, and others slowly transform them. Some food manufacturers use cool water to chill vegetables and fruits to preserve freshness.

Vacuum and Dehydration Processes. Removing air from environments surrounding foods by creating a vacuum in a contained space helps minimize oxidation and other chemical reactions that cause spoilage. Engineers design industrial machinery to remove water efficiently from large quantities of food. Food manufacturers often use mechanical dryers to blow streams of warm, dry air over food. Fans circulate this air, which carries water molecules evaporated from food. Osmotic drying uses chemical solutions containing sodium chloride, sucrose, or other agents. Freeze drying involves ice sublimating from frozen food in a vacuum chamber.

Packaging. Food preservation relies on protective containers or wrappings to block contaminants. Films impede oxygen and moisture from contacting foods. Packaging technology includes films containing antimicrobial preservatives and coatings that are safe to eat. The modified atmosphere packaging process involves machinery that places foods in containers that are injected with gases, including nitrogen, oxygen, carbon dioxide, or noble gases such as argon. Variations of modified atmosphere packing include controlled-atmosphere packaging, which uses scrubber technology to attain more precise gas levels, and vacuum packaging at higher pressures.

Applications and Products

Nutrition. People require consistent access to sufficient nutritious foods to survive. Preservation strategies help provide adequate nourishment to populations worldwide. Aseptic processing and packaging contribute significantly to saving agricultural surpluses, which otherwise would spoil or be discarded. Preservation techniques enable people to have a safe source of food and water when emergency situations interrupt the normal flow of goods. Relief organizations distribute bulk shipments of preserved foods that do not require refrigeration. French manufacturer Nutriset and US producer Edesia Global Nutrition Solutions produce Plumpy'nut, a high-calorie, vitamin-rich paste preserved in foil pouches, which alleviates malnourishment in areas affected by famine or disasters.

Travel, Transportation, and Trade. Food preservation has aided the movement of people for centuries. Travelers, including nomads and migrant workers, often rely on preserved foods to sustain them on journeys. Transportation of preserved foods takes place over the land and seas and through the air. Trucks move preserved foods and beverages from manufacturers to wholesalers and retailers. Engineers have designed special shipping cartons and vehicles to protect foods. Boxes of food are often wrapped with plastic. Technicians remove air between the plastic and the food, inserting gases to create a modified atmosphere to stabilize the food until delivery. Films placed around egg packages absorb shock. Refrigerated trucks keep foods frozen or chilled, and fans circulate air within cargo areas to keep perishables fresh. Many of those trucks contain microprocessors or are regulated by satellites to ensure refrigeration is consistent while traveling.

Many railroad companies use refrigerated cars to move foods. These cars are designed to transport specific preserved foods and can be removed from trains and hauled by trucks to their final destinations. Railyards near ports often have stacks of thousands of containers waiting to be transported inland or to sea. Cargo ships transport large tanks filled with several million gallons of preserved foods. Aseptic preservation processes enable worldwide shipments of vegetables and fruit products. Many preserved foods are shipped by airplane, with Federal Express carrying much of that cargo worldwide. Innovations in transporting preserved foods have enhanced international trade. Unique foods associated with specific geographical areas can be shipped and sold in distant markets within days of harvests, expanding sales of native produce.

Exploration. The availability of preserved foods often determines whether an expedition to remote areas is successful. Historically, explorers traveling for extended periods across land masses and bodies of water relied on salted, cured, canned, and other preserved food to provide them energy and nutrients. Modern explorers also carry preserved foods.

The National Aeronautics and Space Administration (NASA) asked Pillsbury Company food scientists to help them develop preserved foods that would not produce crumbs. Mercury, Gemini, and early Apollo program crews consumed foods contained in tubes. NASA arranged for Oregon Freeze Dry to use its freeze-drying technology to preserve more elaborate meals for astronauts to eat during later Apollo and space shuttle missions.

NASA encourages commercial businesses to adapt its food preservation and packaging technology, granting permission to those businesses that want to use these innovations for preserving and packaging their food products. In the 1980s, Sky-Lab Foods used NASA technology to manufacture freeze-dried meals in bags. Oregon Freeze Dry produces freeze-dried military rations, fruits, vegetables, meats, pet treats, and a line of products for backpackers under the brand name Mountain House. Reflective metals used in space films were adapted for use in packages to protect and insulate foods.

In 2010, NASA sponsored a project examining the feasibility of growing vegetables in space to feed astronauts on possible missions to Mars or colonists on a moon base. Orbitec Technologies assisted NASA scientists in determining ways to create gardens on spacecraft. This program supplemented ongoing plant experiments on the International Space Station and attempts by Martek Biosciences in the 1990s to cultivate algae to create oil with polyunsaturated fatty acids for lengthy missions.

Military. Since ancient times, armies have preserved foods to serve as military rations. These foods boost morale by providing soldiers with familiar meals similar to those they consumed at home. Quartermasters distribute preserved food provisions to wounded soldiers in military hospitals and to prisoners of war. During the late twentieth century, military forces began supplying troops with Meals, Ready-to-Eat (MRE). These preserved foods and drinks, resembling those eaten in space, are packaged in pouches. MRE manufacturers process foods, such as beef stew, barbecued chicken, and cultural favorites, such as curry and Vegemite, with special techniques to preserve them for consumption under the adverse conditions associated with military deployments. Soldiers often combine MREs to concoct mixtures that have become part of military tradition.

The US Department of Defense secures MREs from several manufacturers, including International Meals Supply, Wornick, Sopakco, and Ameriqual. International Meals Supply makes MREs for military units worldwide and produces MREStars for civilians. The other MRE manufacturers also make versions for nonmilitary customers. Applications of MRE manufacturing technology include producing energy foods for athletes and survival foods for use in emergencies. Governments, hospitals, and safety and relief agencies acquire MRE for use in crises.

Careers and Course Work

People seeking careers associated with food preservation can pursue several educational options depending on their professional interests and goals. Most industrial and government food preservation career paths require employees to have a Bachelor of Science degree. Food preservation professionals can find positions with both industrial and academic employers wanting to improve techniques to protect foods. Undergraduate classes focusing on food science, nutrition, agricultural engineering, or animal and dairy science provide students with a fundamental comprehension of how sciences are applied to cultivating, harvesting, and preserving agricultural resources.

An interdisciplinary approach expands students' employability. Studying related scientific and technological fields, especially microbiology, chemistry, and engineering, can qualify students for entry-level positions in industries using food preservation techniques or prepare them for further study. Food manufacturing industries recruit people with engineering degrees and work experience who can design machinery to preserve food or can incorporate robotics and automation into packaging processes. Computer expertise is needed to write programs monitoring preservation processes.

Graduate degrees, usually a master's degree and sometimes a doctorate, in specialized fields are usually needed for research positions involving food preservation work at industrial, government, or academic laboratories. Veterinary science degrees prepare professionals focusing on food preservation issues associated with livestock products. Faculty positions enable qualified personnel to teach students or perform research at university experiment stations. Government agencies, especially the USDA and FDA, hire employees with food preservation knowledge to work in diverse research, education, and administrative roles.

Social Context and Future Prospects

International humanitarian and agricultural groups emphasize the need for continued food preservation research to mitigate hunger and malnutrition. In 2021, the Food and Agriculture Organization of the United Nations stated that, in 2020, between 720 and 811 million people worldwide experienced hunger. In 2022, that number remained around 783 milion, with over 300 million people dealing with acute hunger. Aid workers teach impoverished people basic food preservation techniques so that they can stockpile foods. The COVID-19 pandemic and the recession in the early twenty-first century made bulk buying of foods attractive to many people, who then became interested in preserving these foods to store them for longer periods. The number of people growing gardens or purchasing produce from farmers markets increased, making home food preservation more popular. These people were motivated not only by economic considerations but also by a desire to control the quality of their food.

Manufacturers expect food technologists to improve preservation techniques so that their foods remain fresher longer than those of their competitors. Packaging research and creative technological advances, such as aseptic methods and antimicrobial films, represent a growing component of the food preservation industry. Industries have also asked scientists to use more natural preservatives and avoid synthetic chemicals because many consumers refuse to purchase foods containing any additives that might be detrimental to their health. This has led researchers to look into using biopreservatives. The concepts of isochoric freezing and cold plasma technology were also being studied. Food preservation researchers strive to advance and patent unique methods incorporating bacteriophages (bacteria-eating viruses), enzymes, and other innovative scientific concepts to combat microorganisms while producing affordable, nutritious foods with long shelf lives.

Bibliography

Batiha, Gaber El-Saber, et al. "Application of Natural Antimicrobials in Food Preservation: Recent Views." Food Control, vol. 126, 2021. doi:10.1016/j.foodcont.2021.108066. Accessed 15 Mar. 2022.

Belasco, Warren, and Roger Horowitz, editors. Food Chains: From Farmyard to Shopping Cart. U of Pennsylvania P, 2009.

Branen, A. Larry, et al., editors. Food Additives. 2nd ed., Marcel Dekker, 2002.

"Executive Summary - The State of Food Security and Nutrition in the World 2020." Food and Agriculture Organisation of the United Nations, www.fao.org/3/ca9692en/online/ca9692en.html#chapter-executive‗summary. Accessed 27 May 2024.

"Food Irradiation." US Environmental Protection Agency, 9 Feb. 2022, www.epa.gov/radtown/food-irradiation. Accessed 15 Mar. 2022.

“Food Waste by Country: Who’s the Biggest Waster in 2023?” IFCO, 26 Oct. 2023, www.ifco.com/countries-with-the-least-and-most-food-waste. Accessed 27 May 2024.

“A Global Food Crisis.” World Food Programme, 2024, www.wfp.org/global-hunger-crisis. Accessed 27 May 2024.

Hirschi, Katharina. “Isochoric Freezing: The Future of Food Preservation.” Tellus, tellus.ars.usda.gov/stories/articles/isochoric-freezing-future-food-preservation. Accessed 27 May 2024.

Kurlansky, Mark. Salt: A World History. Walker, 2002.

Lelieveld, Huub L. M., et al., editors. Food Preservation by Pulsed Electric Fields: From Research to Application. Woodhead, 2007.

Nelson, Philip E., editor. Principles of Aseptic Processing and Packaging. 3rd ed., Purdue UP, 2010.

Rahman, Mohammad Shafiur, editor. Handbook of Food Preservation. 3rd ed., CRC Press, 2020.

Shephard, Sue. Pickled, Potted, and Canned: How the Art and Science of Food Preserving Changed the World. Simon & Schuster, 2000.