Food additives are organic substances that are intentionally added to food in small quantities during production or processing to improve the organoleptic quality (colour, flavour, appearance, taste and texture) of the food. Food preservative is a class of food additive that help to prevent food spoilage by preventing the growth and proliferation of pathogenic microorganisms like Clostridium spp , Bacillus cereus and Staphylococcus aureus. This can be achieved by bringing down the pH of the food so as to make the environment unfavourable for these microbes. This report aims to review the available literature on the various effects of food additives and preservatives on man as a result of the indiscriminate uses by food producers and food consumers. Many effects like food allergies, food intolerance, cancer, multiple sclerosis (MS), attention deficit hyperactivity disorder (ADHD), brain damage, nausea, cardiac disease among others have been reported.
Functions of Food Additives
Additives are used in foods for the following reasons:
To maintain product consistency: Emulsifiers give products a consistent texture and prevent them from separating. Stabilizers and thickeners give smooth uniform texture. Anticaking agents help substances such as salt to flow freely. To improve or maintain nutritional value: Vitamins and minerals are added to many common foods such as milk, flour, cereal and margarine to make up for those likely to be lacking in a person’s diet or lost in processing. Such fortification and enrichment has helped reduce malnutrition among the U.S. population. All products containing added nutrients must be appropriately labeled. To maintain palatability and wholesomeness: Preservatives retard product spoilage caused by mold, air, bacteria, fungi or yeast. Bacterial contamination can cause food borne illness, including life-threatening botulism. Antioxidants are preservatives that prevent fats and oils in baked goods and other foods from becoming rancid or developing an off flavour. They also prevent cut fresh fruits such as apples from turning brown when exposed to air.
To provide leavening or control acidity/alkalinity: Leavening agents that release acids when heated can react with baking soda to help cakes, biscuits and other baked goods to rise during baking. Other additives help to modify the acidity and alkalinity of foods for proper flavour, taste and colour. To enhance flavour or impact desired colour: Many spices, natural and synthetic flavours enhances the taste of foods. Colours, for instance help to enhance the appearance of certain foods to meet consumer expectations.To maintain product consistency and quality: They help to improve or maintain nutritional value, maintain palatability and wholesomeness, provide leavening, control pH, enhance flavor, or provide colour.
Classification of Food Additives
Food additives can be divided into several groups, although there is some overlap between them.
Antimicrobial Agents: These prevent spoilage of food by microorganisms. These include not only vinegar and salt, but also compounds such as calcium propionate and ascorbic acid, which are used in products such as baked foods, salad dressings, cheeses, margarines, and pickled foods (Abdulmumeen et al., 2012).
Antioxidants: An anti-oxidant is a substance added to fats and fat-containing substances to retard oxidation and thereby prolong their wholesomeness, palatability, and, sometimes, keeping time. An anti-oxidant should not contribute an objectionable odor, flavor, or color, to the fat or to the food in which it is present. It should be effective in low concentrations, and be fat soluble. Also, it should not have a harmful physiological effect. Some anti-oxidants used in foods are butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and teriarybutyl hydroquinone (TBHQ), which are all phenolic substances (Dalton, 2002). Thiodipropionic acid and dilauryl thiodipropionate are also used as food anti-oxidants. The Joint FAO/WHO Expert Committee on Food Additives has recently considered the Acceptable Daily Intakes (ADls) of BHA and BHT and set them at 0-0.5 mg/kg body weight for BHA and 0-0.3 mg/kg body weight for BHT. Naturally occurring substances that act as anti-oxidants are tocopherols. The tocopherols act as biological anti-oxidants in plant and animal tissues, but they are rarely used as additives because they are more expensive than synthetic anti-oxidants (Sunitha and Preethi, 2000).
Colouring Agents: These include color stabilizers, color fixatives, color retention agents, etc. They consist of synthetic colours and those from natural sources. Even though most colors do not add any nutritive value to foods, without certain colours most consumers will not buy or eat some foods. Thus, colours are frequently added to restore the natural ones lost in food processing or to give the preparations the natural colour we expect. A number of natural food colours extracted from seeds, flowers, insects, and foods, are also used as food additives. One of the best known and most widespread red pigments is bixin, derived from the seed coat of Bixa orellana, the lipstick pod plant of South American origin. Bixin is not considered to be carcinogenic. The major use of this plant on a world-wide basis, however, is for the annatto dye, a yellow to red colouring material extracted from the orange-red pulp of the seeds. Annatto has been used as colouring matter in butter, cheese, margarine, and other foods. Another yellow colour, a carotene derived from carrot, is used in margarine. Saffron has both flavouring and colouring properties and has been used for colouring foods. Turmeric is a spice that gives the characteristic colour Food Acids: Food acids are added to make flavors “sharper”, and also act as preservatives and antioxidants. Common food acids include vinegar, citric acid, tartaric acid, malic acid, fumaric acid, and lactic acid.
Preservatives: A preservative is defined as any substance which is capable of inhibiting, retarding, or arresting, the growth of micro-organisms, of any deterioration of food due to micro-organisms, or of masking the evidence of any such deterioration. It is estimated that nearly one fifth of the world’s food is lost by microbial spoilage. Chemical preservatives interfere with the cell membrane of micro-organisms, their enzymes, or their genetic mechanisms. The compounds used as preservatives include natural preservatives, such as sugar, salt, acids, etc, as well as synthetic preservatives. The safe-use period of many foods is greatly extended through the addition of preservatives, which retard spoilage, preserve flavour and colour and keep oils from turning rancid. Preservatives protect foods, such as cured meats, from developing dangerous toxins, such as botulism, a food poisoning illness (Sunitha and Preethi, 2000).
Chelating agents: Chelating agents are not anti-oxidants. They serve as scavengers of metals which catalyze oxidation. Recommended usage levels for citric acid typically vary between 0.1 and 0.3 per cent with the appropriate anti-oxidant at levels ranging between 100 and 200 ppm). EDTA is a chelating agent permitted for use in the food industry as a chemical preservative. Calcium disodium EDTA and disodium EDTA have been approved for use as food additives by the United States Food and Drug Administration. The chelating agents are used to prevent discolouration, flavour changes, and rancidity that might occur during the processing of foods, examples include citric acid, malic acid, and tartaric acid (Sunitha and Preethi, 2000).
Nutrient Supplements: Nutrient supplements restore values lost in processing or storage, or ensure higher nutritional value than what nature may have provided. When foods are processed, there may be loss of some nutrients and additives may be added to restore the original value. For example, to produce white flour, wheat is milled in such a way as to remove the brown coloured part of the grain, which is rich in vitamins and minerals. To restore the nutritive value, thiamine, nicotinic acid, iron and calcium, are added to the flour. Similarly, vitamin C is added to canned citrus fruits to make up the loss of the vitamin during processing (Sunitha and Preethi, 2000).