Preservative

A preservative is a type of food additive used to prevent or slow spoilage. Preservatives lengthen the life span of many foods and beverages, so they do not go rancid, discolor, or change in texture. Both natural and artificial preservatives exist. Many foods, including some organic and fresh foods, contain preservative. They can also be found in medications, cosmetics, and other products. In the United States, preservatives in most foods are regulated by the US Food and Drug Administration (FDA), while meat and poultry products are also regulated by the US Department of Agriculture, and preservatives must be listed on labels. While some have been linked to increased cancer risk, preservatives approved for use in the United States must meet the FDA’s safety standard of a reasonable certainty of no harm under their intended conditions of use. In 2025, the FDA introduced a strengthened post-market review program for chemicals already in the food supply, allowing previously approved preservatives to be reassessed as new safety data becomes available. Prior to the development of preservatives, individuals used many techniques to make foods last longer such as curing, canning, and pickling.

Background

People have been practicing the art of preserving food since ancient times. Prior to learning preservation methods, food had to be eaten immediately. As soon as food is harvested, it begins to spoil. Humans had to determine ways to stop or slow down this process to extend the life of their food. When food became scarce, people usually moved to places where they could find something to eat, such as warmer climates during the cold months. Preservation allowed people to keep food for longer periods, thus permitting them to remain in one place and build communities.

Basic food preservation methods emerged throughout the years. In ancient times, drying was a popular way to keep food for later consumption. This method can be traced to early human societies around 12,000 BCE. The sun and wind were used to naturally dry fish and game meat as well as fruits and vegetables. During the Middle Ages, the Romans built huts to house foods for drying and used fire to aid in the process; this also smoked the foods and further preserved them.

People who lived in cold climates took advantage of the low temperatures to freeze foods and prolong their storage. Individuals also stored foods in cool cellars and caves. Later, icehouses and iceboxes were built to keep food on ice. These eventually became the modern refrigerator.

The process of fermentation was discovered by accident when microorganisms naturally fermented sugars in grains. The moist atmosphere helped microorganisms in the grains grow and then ferment with the sugars in the grains to produce alcohol. This process also made foods more nutritious because the microorganisms produced vitamins as they fermented.

Pickling was another technique used to keep food fresh. Early on, people placed food in wine and beer to help extend its life. When the liquid soured, it gave the food a pleasantly sour taste. Vinegar and other acids were soon used to pickle foods. Individuals began to use the pickling juices to make sauces, condiments, relishes, and more.

When curing, also known as dehydration, people used salt to draw the moisture out of foods to prevent them from becoming rancid. The use of sugar and honey to keep foods fresh was also common during this time. This led to the creation of jams and jellies when people heated fruit with sugar to preserve it. Canning is a newer form of preserving foods that was developed in the late 1700s by French chef Nicolas Appert. He discovered that he could use heat to seal foods in glass bottles to extend their shelf life.

Overview

Although natural preservatives such as salt, honey, and sugar had been used for centuries, over time, artificial preservatives were developed to keep food from spoiling. Preservatives work in several ways. They act as antimicrobials to block the growth of molds, bacteria, and yeasts. They work as antioxidants to slow the oxidation process (chemical breakdown of food in the presence of oxygen) of fats and lipids that cause spoilage to foods. They also serve as chelating agents to bind metal ions and slow oxidation and discoloration in foods. In the 2020s, food scientists have also developed “clean-label” preservation methods, which use natural antimicrobial compounds and biopreservatives derived from plants and microorganisms as alternatives to synthetic additives.

Propionic acid naturally occurs in many types of foods, such as strawberries, apples, grains, and cheese. Propionic acid prevents mold in breads and baked items. Benzoates (benzoic acids), which are found in cranberries, and sorbates (sorbic acids) block the growth of fungus. Both are used in numerous foods, such as beverages, jams, pickled foods, meats, condiments, cheeses, and margarines, to keep them fresh.

Nitrites and nitrates keep cured and processed meats, such as bacon and deli meats, pink in color and prevent them from turning brown. Derived from salt, they also enhance flavor. Nitrites and nitrates prevent the bacterium Clostridium botulinum from growing on foods.

Sulfur dioxide, a type of sulfite, is a preservative found in dried fruits, wines, and other processed foods. The compound inhibits microbial growth at the cellular level. It can interfere with the way cells work and even destroy genetic material. Sulfites can keep dried fruits such as golden raisins from browning by preventing the Maillard reaction, which is the chemical process between amino acids and reducing sugars. It gives raisins their dark color and distinct flavor. Some people have sensitivities to sulfites, especially certain individuals with asthma. These can cause mild to severe reactions such as breathing problems.

Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) slow oxidation in foods to prevent them from spoiling. They are commonly used to prevent oils from going bad. Fatty acids and lipids are damaged by oxygen, which creates an off-putting smell and flavor. Other examples of antioxidant preservatives include tert-butylhydroquinone (TBHQ) and propyl gallate. In 2026, the FDA began a reassessment of BHA and identified BHT for further safety review, reflecting increased attention to synthetic antioxidant preservatives.

Some foods contain enzymes that cause them to metabolize after harvest. The enzyme polyphenol oxidase (PPO) contributes to apples or potatoes turning brown when they are cut and their flesh is exposed to the air. Citric acid and ascorbic acid (vitamin C) can be used to counteract polyphenol oxidase and prevent the browning process. The chelating agent ethylenediaminetetraacetic acid (EDTA) is used to stop bacterial and fungal enzymes from spoiling foods. EDTA can also be used to prevent discoloration in foods and other products.

Concerns about some long-used food additives have led to increased review by regulatory agencies as new safety information becomes available.

Bibliography

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