An introduction to Preservatives
A preservative is a substance or a chemical that is put into products like packaged food products, bottled beverages, pharmaceutical / chemical drugs, varnishes/ paints, biological samples taken from living organisms, beauty products, and many other different products to prevent the process of decomposition by microbial growth or by undesired chemical change.
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Generally, preservation is done in two modes, that is chemical and physical respectively. Chemical protection deals with adding chemical compounds to the product. Physical maintenance deals with processes like refrigeration or drying up of products. Preservative food additions shrink the risk of foodborne infections, narrow the chances of microbial spoilage, and preserve fresh characteristics and nutritional quality of the food. Some physical processes for food preservation consist of dehydration, UV radiation, drying by freezing, and refrigeration manufacture industry.
Chemical Food Preservatives
There are three categories of chemical preservatives commonly used in foods:
Benzoates (like sodium benzoate)
Nitrites (like sodium nitrite)
Sulphites (like sulphur dioxide)
If we pay attention to the ingredient labels of different food packages, we will frequently come across the names of different types of chemical preservatives. Another common chemical preservative that we will commonly come across on food packet labels is sorbic acid. All of these chemical preservatives either inhibit the activity of microbes such as bacteria or destroy them. Chemical preservatives boost food product usage to a substantial level.
Examples of preservatives used in food
The following are some examples of different types of preservatives:
Potassium Nitrate
Erythorbic Acid
Benzoic acid
Sodium Benzoate
Calcium Sorbate
Antioxidants are used as preservatives by slowing down how quickly a product might spoil. The examples include Butylated Hydroxyanisole (BHA), Butylated Hydroxytoluene (BHT), and Ascorbyl Palmitate.
Antioxidants In Food Preservation
Antioxidants used for food preservations have two categories – Naturally occurring antioxidants and artificial antioxidants. Both of them are used as food preservatives. Oxidation readily affects the quality of food and shortens its life by incredibly modifying its semblance, colour, sensory attributes, and nutritive quality.
Common Antioxidants in Food Preservation
Some examples of potential natural antioxidants in food preservation and their sources are tocopherols (found in nuts and seeds), ascorbic and citric acids (found in citrus fruits), carotenoids (found in fruits and vegetables) and phenolic compounds (found in herbs and spices, grape seeds). Plant phenolic extracts are prevalently used in the preservation of seafood, meat, fats and oils. Ascorbic acid is extensively used in the preservation of juices, cereals, jams, treated meats and some canned foods. At the same time, tocopherols have their applications in the preservation of grains, meat and poultry products, butter, oils, and other dairy products. Rosemary extract is predominately used as an antioxidant preservative in the continents of Europe and North America.
Sodium Preservative In Food
The most extensively used sodium preservative in food is sodium benzoate. Sodium benzoate is predominantly known as a preservative used in processed foods and beverages to extend consumption life, though it has many other uses. It's an odourless, crystalline powder manufactured by merging benzoic acid and sodium hydroxide.
Another extremely used sodium preservative in food is sodium nitrate. Sodium nitrate is a preservative that is used in some processed meats like bacon, jerky and luncheon meats. But it could increase your heart disease risk. It's anticipated that sodium nitrate may damage your blood vessels, making your arteries more likely to harden and narrow, which can lead to heart disease.
Role of Salt In Food Preservation
Salt commonly plays a vital role in the fermentation of foods. Fermentation is a common phenomenon for preserving foods, in which fresh foods are converted to desirable foods that can be kept for more extended periods than their new part for the actions of particular microbes. The common belief for salt in food preservation is that salt kills bacteria, but for the actual matter of fact, salt does not preserve food directly. Instead, it has to play an essential role in a critical process called osmosis. Salt can always play a role in the development of physical attributes of foods that are beneficial for processing or developing final product qualities. For example, salt levels play a significant role to control the adhesive properties of some doughs, which is the process of some baked goods.
Salt can play an essential role in the development of physical properties of foods that are beneficial for the process and progress of final product qualities. As an example, salt levels play an essential role in controlling the stickiness of some doughs which eases the processing of some baked materials.
Natural vs. Artificial Food Preservatives
Preservatives are termed as any substances that are added to food before it is consumed. Food preservatives are generally used for extending shelf life, flavouring and colouring to improve the taste and appearance of the food and nutritional supplements such as vitamins and minerals. Indirect food additives include the contaminants from manufacturing, storing and packaging processes.
Food preservatives are used to protect your food from microbes that might contaminate or rot the food. They protect food from poisoning and keep food looking and tasting fresh. However, many preservatives used today are chemical in origin and might have dangerous side effects.
Artificial Preservatives
Artificial preservatives are chemical substances that stop or delay the growth of bacteria, spoilage and discolouration. They can be added to the food or sprayed on the food.
Types of Artificial Preservatives Food
Antioxidants
Antimicrobial agents
Chelating agent
In antimicrobials come the Benzoates, Sodium benzoate, Sorbates and Nitrites.
Antioxidants include Vitamin E, Vitamin C, Sulfites, whereas the Butylated hydroxytoluene (BHT) Chelating agent include Citric acid, Disodium ethylenediaminetetraacetic acid (EDTA), and Polyphosphates.
Harmful Food Preservatives
Food additives are used to stop bacterial growth to keep the food fresh. Although, there are certain preservatives in food that are harmful if taken in more than the prescribed limits. Certain harmful food preservatives are Benzoates, Butyrates, and Caramel.
Types of Chemical Preservatives
According to FSSAI Chemical preservatives are divided into two categories, (i) Class I Preservatives (obtained from natural sources), (ii) Class II Preservatives (obtained synthetically).
Importance of Preservatives
Preservatives play an essential role in many products used every day to help prevent the growth of harmful microorganisms and to protect products from contamination or spoilage. They are made of natural chemicals such as salt or alcohol, and they can also be man-made, or synthetic chemicals. Natural or organic chemicals are not certainly healthier than synthetic or man-made chemicals. In reality, artificial preservatives have long been used in food preparation because they are effective in small amounts. They include sodium nitrate, sodium benzoate and propionate.
Nowadays, preservatives, including food and colour additives, are more precisely studied, and monitored than at any other time in history. FDA (Food and Drug Administration) has the main legal responsibility for determining the safe use of preservatives. The manufacturer or other sponsor must obtain approval from the FDA before using a substance already approved for one use in another application or to add a new food preservative to the market. They are required to provide scientific data representing that the substance is safe for its intended use.
Fun Facts
As jams and jellies contain much more sugar than any other kind of sweet or deserts. By the process of osmosis, the sugar is extracts the water from food. In this way, this process helps in food preservation. This is the same reason why our mothers use to put in extreme quantities of salt and oil in the pickles. The pickles have an intense taste due to this.
Hence we get to know about the importance of food preservatives and how it is helpful for us to preserve our food. The article explains different types of food preservatives as well as harmful food preservatives.
FAQs on Chemicals Used as Food Preservatives
1. What are the main classes of chemical food preservatives as per the NCERT syllabus?
According to the CBSE syllabus for the 2025-26 session, chemical food preservatives are mainly categorised into two classes:
- Class I preservatives: These include natural substances like table salt, sugar, and vegetable oils, which are generally considered safe and have a long history of use.
- Class II preservatives: This class includes synthetic chemicals like benzoates, sorbates, and nitrites, which are added in controlled amounts to prevent microbial growth.
2. What are the two most common chemical preservatives used in processed foods and beverages?
The two most common and widely used chemical food preservatives are sodium benzoate and salts of sorbic acid. Sodium benzoate is particularly effective in acidic foods like soft drinks, jams, and pickles. Sorbic acid and its salts (like potassium sorbate) are used to inhibit the growth of mould and yeast in products like cheese, wine, and baked goods.
3. How does a chemical preservative like sodium benzoate actually work to prevent food spoilage?
Sodium benzoate works by inhibiting the growth of microorganisms like bacteria and yeast. Its effectiveness depends on the acidity of the food. In an acidic environment (low pH), it converts to benzoic acid, which is the active antimicrobial agent. Benzoic acid is absorbed into the microbial cells, where it interferes with key metabolic functions, such as the activity of enzymes required for energy production, ultimately stopping the microbes from multiplying and causing spoilage.
4. What is the specific role of antioxidants as food preservatives?
The primary role of antioxidants as food preservatives is to prevent the oxidation of food components, especially fats and oils. Oxidation leads to rancidity, which causes unpleasant odours and flavours, making the food inedible. Antioxidants like Butylated Hydroxytoluene (BHT) and Butylated Hydroxyanisole (BHA) are more reactive towards oxygen than the food itself. They sacrifice themselves by getting oxidised first, thereby protecting the food and extending its shelf life.
5. How does the preservative action of table salt differ from that of a chemical like potassium metabisulphite?
The preservative actions of table salt and potassium metabisulphite are fundamentally different.
- Table salt (Sodium Chloride): It acts primarily through a physical process called osmosis. A high concentration of salt draws water out of microbial cells, dehydrating them and creating an environment where they cannot survive or reproduce.
- Potassium Metabisulphite: This is a chemical preservative that works by releasing sulphur dioxide (SO₂). SO₂ is a potent inhibitor of enzymes and prevents the growth of yeasts, moulds, and bacteria. It acts through a direct chemical interference with the microbes' metabolism, rather than by dehydration.
6. Why are different preservatives used for different types of food products?
Different preservatives are used because their effectiveness is highly dependent on the food's properties, particularly its pH level (acidity) and composition. For example:
- Benzoates are most effective in acidic foods (pH below 4.5) like fruit juices and carbonated drinks.
- Sorbates work over a broader pH range and are excellent against moulds, making them suitable for cheese and baked goods.
- Nitrites and Nitrates are specifically used in cured meats to prevent the growth of Clostridium botulinum bacteria and to preserve colour.
7. Are chemical food preservatives completely safe for consumption?
Chemical food preservatives are considered safe for consumption when used within the limits set by food safety authorities like the FSSAI in India. These limits, known as the Acceptable Daily Intake (ADI), are established after extensive testing. However, excessive consumption or individual sensitivities can pose health risks. For instance, sulphites can trigger allergic reactions in some individuals, while concerns exist about the formation of potentially harmful compounds from nitrites under certain conditions. Therefore, their use is strictly regulated.
