Introduction
Food additives have been used in food preparations from prehistoric times to perform various functions. Processing of food into variety of products involves use of various food ingredients called as additives. Technological developments in food processing have greatly encouraged the use of these additives but most of these additives and colourants are synthetic in nature.
Food additives are used to provide protection against microorganisms, increase quality and extend shelf life in many stages, from production to consumption of food (Branen et al. 2001). The use of these additives is a well-acquired practice but may be associated with certain risks. Used judiciously, food additives promote food safety, maintain nutritional quality and improve the texture, taste and appearance of foods.
Every food additive has been allotted a unique number in the International Numbering System (INS), adopted and extended by the Codex Alimentarius used to uniquely identify a food additive in legislation and for labelling purposes. Number ranges have been pre-assigned to food additive classifications, so as to give information about the main purpose of the additive, even without knowing the name of the additive (Tomaska & Taylor 2014). INS number for some additives is indicated in Table 1.
Food Additives
The International Codex Alimentarius Commission (CAC) defines food additives as “any substance not normally consumed as a food by itself and not normally used as a typical ingredient of the food, whether or not it has nutritive value, but added to the food with the intention of achieving a specific purpose, known for having safe dose levels and subjected to legal permission.” Food additives are substances added in the processing, preparation, packaging, transportation, preservation and storage stages (Luckey 1968; Emerton & Choi 2008)
Types of Food Additives
There are four general categories of food additives: nutritional additives, processing agents, preservatives, and sensory agents.
1. Nutritional Additives
Nutritional additives are utilised for the purpose of restoring lost or degraded nutrients during processing. Fortification and enrichment of certain foods are carried out in order to correct dietary deficiencies, or adding nutrients to food substitutes. Vitamins are commonly added to many foods in order to enrich their nutritional value (Chaudhary 2010). For example, vitamins A and D are added to dairy and cereal products.
2. Processing Agents
A number of agents are added to foods in order to aid in processing or to maintain the desired consistency of the product such as emulsifiers, stabilisers, thickening agents, gelling agents, and chelators. Emulsifiers are used to maintain a uniform dispersion of one liquid in another, such as oil in water.
Stabilisers and thickeners are mainly polysaccharides such as starches, gums, or proteins, like gelatin. The primary function of these compounds is to increase the viscosity of the final product. Chelating, or sequestering, agents protect food products from many enzymatic reactions that promote deterioration during processing and storage (Chaudhary 2010).
3. Preservatives
Food preservatives are mainly classified thus; antioxidants and antimicrobials. Antioxidants are compounds that retard or prevent the deterioration of foods by oxidative mechanisms. Antioxidant reacts with the free radicals (called free radical scavengers) to slow the rate of autoxidation. These antioxidants include the naturally occurring tocopherols (vitamin E derivatives) and the synthetic compounds butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylhydroquinone (TBHQ).
Antimicrobial agents inhibit the growth of spoilage and pathogenic microorganisms in food. Sodium chloride (NaCl) is probably the oldest known antimicrobial agent. Organic acids, including acetic, benzoic, propionic, and sorbic acids, are used against microorganisms in products with a low pH. Sulfur dioxide and sulfites are used to control the growth of spoilage microorganisms in dried fruits, fruit juices, and wines (Chaudhary 2010).
4. Sensory Agents
Food Colourants
Colours are used to enhance the visual properties of foods. A colour additive is any dye; pigment or substance which when added to food is capable of imparting colour to the product so as to maintain appearance and freshness by restoring the colour lost during processing. Colourants are usually added to processed foods such as candies, snacks, margarine, cheese, soft drinks, and jam/jelly, gelatin, pudding and pastry fillings (FDA 2010).
Classification of Colourants
Natural Colourants
Natural food colourants are demanded by people for their long- or short-term effects as well as for their reliability, functionality, biological potential and health effects. Consumers perceive natural colourants as safer than synthetic colourants which are thought to be harmful (Martin et al. 2016).
Natural colourants are less stable to heat, light or pH (Karaali et al. 1993). Natural colouring matters are synthesised by plant and animal organisms or microorganisms and they naturally exist in them, e.g., annatto, anthocyanins, caramel, carotenes, curcumin, lycopene.
Synthetic Colourants
The substances which are not found in nature due to chemical structures and obtained by chemical synthesis are known as synthetic colourants. Synthetic food colourants surpass natural colourants due to their high colouring ability, various colour tone, homogeneous colour distribution, brightness, stability, and ease of application (Griffiths, 2015).
With high water and oil dissolution properties, shelf life of the synthetic colourants is quite long. Synthetic colourants are divided into three groups according to their solubility into water-soluble synthetic colours, fat-soluble synthetic colours and lake colours (Demirag & Uysal, 2006).
Water-soluble synthetic colours mainly include Sunset Yellow, Tartrazine, Erythosine, Brilliant Blue FCF and Allura Red AC. Fat-soluble synthetic colours are insoluble in water and are not allowed to be used for food colouring because of their toxic properties, e.g., Penso SX, Red XO.
Lake colourants are water-insoluble precipitation of aluminum hydrate substrate and are produced in the form of very fine powders (Downham & Collins 2000). As they are not soluble in water, oil and other solvents, they are dispersed in food and produce colour (Demirag & Uysal, 2006).
Associated Risks
Despite the benefits attributed to food additives, for several years there have also been a number of concerns regarding the potential short- and long-term risks of consuming these substances. As for many of the benefits mentioned, there is not always adequate scientific proof of whether or not a particular additive is safe.
Today, all new food additives undergo a safety assessment to minimise any potential adverse effects of food additives to human health. An extensive range of animal and other tests have been devised to assess health risk to humans. This safety evaluation at a global level is performed by a scientific advisory body to the Food and Agriculture Organization (FAO) and World Health Organization (WHO), namely the Joint FAO/WHO Expert Committee on Food Additives (JECFA).
The food additives that are GRAS-certified are only permissible to be used. GRAS substances are defined as having safety adequately shown through scientific procedures when experts with appropriate training and experience generally agree the common knowledge about the product supports the safe use of the product as intended and under the conditions of their intended use.
Conclusion
Food additive is a chemical substances added to foods to produce specific desirable effects. Although certain safety issues associated with some food additives continue to be debated and such concerns need to be addressed using the most advanced testing protocols including rigorous toxicological analysis prior to their approval for use in the industry. Feeding studies are carried out using animal species (e.g., rats, mice, dogs) in order to determine the possible acute, short-term, and long-term toxic effects of these chemicals.
