Afood additive is defined as a substance or mixture of substances, other than a base foodstuff, which is added to food during production, processing, storage or packing. According to the Codex Alimentarius definition, a food additive refers to any substance that is not normally consumed as a food by itself and not used as a typical ingredient of the food, regardless of its nutritive value. The addition of this additive to food is intended for a technological (including organoleptic)purpose in the manufacture, processing, preparation, treatment, packing, packaging, transport or holding of such food results. On the other hand, it may be reasonably expected to result (directly or indirectly) in it or its by-products becoming a component of or otherwise affecting the characteristics of such foods. According to the London Food Commission (1988), the food additives in use today can be divided roughly into (i) Cosmetics, (ii) Preservatives and (iii) Processing aids. At present, there are about 3,794 different additives. Of these, over 3,640 are used purely as cosmetics, 63 as preservatives and 91 as processing aids. Moreover, the Food and Drug Administration (FDA) classifies food additives into three categories. Indirect food additives comprise packaging materials such as paper, plastic, cardboard and glue that come in touch with food. Direct food additives consist of preservatives, nutritional supplements, flavours and texturisers that are added to food. Colour additives are used to change or enrich the colour of a food (Taylor, 1980).

Functions of additives
Food additives may be used in a food system for the following purposes:

• Improve or maintain the nutritional quality of a food, keeping the calorie value unaltered

• Maintain the palatability and wholesomeness

• Provide leavening and pH control for backed foods

• Enhance the flavour and desired colour

Additives and their functions
Over 3000 different chemical compounds as recommended by the FDA are used as food additives. These additives are categorised into different groups depending on their functions in food systems. A few food additives are summarised below.



• Anti-microbial agents: Substances that kill, inactivate or retard the growth of micro-organisms

• Antioxidants: Substances that retard or prevent oxidation reactions that would result in
the development of off-flavours, discolouration and the loss of nutritive value

• Appearance/control agents: Substances that alter or preserve the colour (saturation or lightness) of a food, for example, colour stabilisers and fixatives. These comprise substances other than colour that include glazes, waxes and polish and are applied to solid foods to preserve or improve surface appearance. These also include turbidity promoters, for example, brominated vegetable oil (BVO) and ester gum that are added to fluid foods to produce or stabilise suspended materials.

• Flavour and flavour modifiers: These are substances that impart, supplement, intensify or modify the taste/aroma of a food.

• Moisture control agents: These include substances that maintain or reduce the moisture content of any food, for example, humectants, water-binding agents, protective coatings, anti-dusting agents, anti-coating agents, free-flowing agents and drying agents.

• Nutrients: These substances are used to restore or increase the nutrient value of food (except calories).

• pH control agents: These maintain or alter the active acidity or alkalinity of foods, for example, acid, base or buffer.

• Sequestrants: These substances combine with metal ions and prevent adverse effects.

• Surface tension control agents: Substances that enhance the compatibility of the physical phases of foods (for example, liquid/solid, solid/gas) by affecting the character of the interface such as wetting agents, whipping agents, dispersants and rehydration enhancers.

• Emulsifiers: Substances that help to form or stabilise dispersion of oil and water by accumulating preferentially at the oil-water interface and lessening the tendency of the dispersed particles on combine into separate layers. The emulsifiers used may include firming agents, leavening agents, masticatory agents, stabilisers and thickeners, texturisers and processing aids. The following substances are not recognised as food additives:

• Commonly used additives (salt and sugar)

• Vitamins, minerals and amino acids

• Spices, seasoning and flavours

• Agricultural agents

• Veterinary drugs

Additives and their health effects
Today about 75 percent of the Western diet is made up of various processed foods. Each person consumes, on an average, 3.5–4.5 kg of food additives per year (Miller, 1985; Feingold, 1973). Although most food additives are considered harmless, the rapidly increasing number and types of chemicals added to our food has increased concerns regarding their harmfulness. The FDA, which is responsible for regulating the use of food additives, states that there are more than 3,000 food additives currently cleared for use in the food industry. Once a food additive has been approved by the FDA, it is considered to be fit for human consumption. But, it is important to note that these additives might not be entirely safe for consumption. Some foods and colouring additives have been known to induce allergic reactions, while others are suspected to cause cancer, asthma or birth defects. Although all of the additives have been approved for human consumption, many of them still provoke very vehement responses from the consumers.

Some additives and their effects on human and animal health are summarised below.

Colourants
Tartrazine, which is primarily used by the soft drink industry, is one of the colours most frequently implicated in food intolerance studies (Williams and Cram, 1978). Adverse reactions to tartrazine are apparent in subjects who are sensitive to acetylsalicylic acid. Depending on the test protocol followed, it has been found that 10–40 percent of aspirin-sensitive patients are usually also
affected by tartrazine.

The reactions include asthma (Freedman, 1977), urticaria (Juhlin, 1981), rhinitis (Juhlin et al, 1972) and childhood hyperactivity (Freingold, 1981). Although tartrazine seems to be most frequently associated with adverse reactions, there are also other colouring agents, which cause mental and physical disorders in the human body (Miller and Millstone, 1987).

Curcumin, used mainly in flour, confectionery and margarine, has been found to cause mutations in bacteria and, when fed to pigs, it increases the weight of their thyroid glands causing thyroid damage (Miller and Millstone, 1987). Sunset yellow, used in biscuits, has been found to damage kidneys and adrenals when fed to laboratory rats. It has also been found to be carcinogenic when fed to animals (Miller, 1985).

Carmoisine, used mainly in jams and preserves, was found by the US-certified Color Manufacturers Association to be unavoidably contaminated with low levels of beta-napthylamine, which is a well-known carcinogen. It has also been found to be mutagenic in animal studies (Miller, 1985).

When fed to laboratory rats, amaranth has been found to cause cancer, birth defects, stillbirths, sterility and early foetal deaths. Researches have found that amaranthus can cause female rodents to reabsorb some of their own foetuses. Ponceau 4R, used mainly in dessert mixes, has been found to exhibit a weak carcinogenic action (Miller, 1985; Miller and Millstone, 1987).

Erythrosine, used in candied cherries and children's sweets, has been found to act as a potent neuro-competitive inhibitor of dopamine uptake by nerve endings when exposed in-vitro on a rat brain, (Lafferman and Silbergeld, 1979). From various studies, it has been shown that erythrosine can inhibit the action of other neurotransmitters causing by the concentration of neurotransmitters near the receptors. This functionally enhances the synaptic neurotransmission. It has also been shown that a reduced dopamine concentration may cause childhood hyperactivity.

Caramels, which are used in colas, beer and the alcohol industry, have been found to have adverse effects on the levels of white blood cells and lymphocytes in laboratory animals. Even small doses of ammoniated caramels apparently inhibit the absorption of Vitamin B6 (Miller and Millstone, 1987).

It has been observed that Brown FK, which is used as a colouring agent in fish such as kippers, when fed to mice for long periods, causes potentially hazardous nodules to form in the liver. It has also been found to cause mutations in some bacteria, showing that it may also act as a mutagenic and/or carcinogenic agent in humans (Miller, 1985; Miller and Millstone, 1987).

Preservatives
Benzoates, used mainly in marinated fish, fruit-based fillings, jam, salad cream, soft drinks and beer, have been found to provoke urticaria, angioedema and asthma (Miller and Millstone, 1987; Michaelsson and Juhlin, 1973).

Sulphites, used mainly in dried fruits, fruit juices and syrups, fruit-based dairy desserts, biscuit dough, cider, beer and wine have been linked with pruritus, urticaria, angioedema and asthma. When fed to animals, sulphites have also been found to have a mutagenic action (Miller, 1985).

Nitrates and nitrites, used in bacon, ham, cured meats, corned beef and some cheeses, have been found to cause headache in susceptible individuals. These chemicals have been linked with cancer both in animal and human studies (Taylor, 1983). They have also been found to be mutagenic when fed to mammals.

Butylated hydroxyanisole (BHA), used in soup mixes and cheese spread, has been found to be tumour-producing when fed to rats. In human studies, it has been linked with urticaria, angioedema and asthma.

Monosodium glutamate (MSG), a flavour enhancer, has been associated with a conjunction of symptoms in susceptible individuals, such as severe chest and/or facial pressure and overall burning sensations, similar to the feeling of experiencing a heart attack. MSG has been also found to precipitate a severe headache and/or asthma (Collins- Williams, 1983; Allen and Baker, 1981). MSG has been found to damage the brains of young rodents.

Sweeteners
Saccharin, used as sweetening tablets and widely used by the soft drink and sweet food industry, has been shown to produce cancer when tested on animals (Wynn and Wynn, 1981; Reuber, 1978). Saccharin has also been found in animal studies to be mutagenic, and it inhibits growth and causes congenital malformations (Batzinger, 1977).

Aspartame (used in the soft drink and sweet industry) when fed to rats, was found to double the level of phenylalanine in their brains, which re-doubled when other carbohydrates were consumed at the same time.

The consumption of sucrose was not only seen to worsen the behaviour of young offenders, but when given to children diagnosed as hyperactive, these foods seemed greatly to increase their restless and destructive behaviour (Prinz, 1980). Excessive refined carbohydrate consumption leads to a disordered carbohydrate metabolism, especially to reactive hypoglycaemia, which in turn has been found to be particularly prevalent among violent offenders. Reactive hypoglycaemia has also been associated with diverse personality and psychiatric disorders, such as neuroses, panic attacks, agoraphobia and schizophrenic episodes (Tuormaa, 1991).

Conclusion
India has large population of over 1000 million, out of which 350 million live in urban areas. Processed foods will become the mainstay for those who live in the cities sooner or later. The global processed food business is around Rs 16,000 billion, while India’s contribution is Rs 1,400 billion. The food-processing sector has been referred to as a ‘sunrise industry’, and several efforts are being made to give a big thrust to this sector. However, there are many types of food hazards prevalent throughout India. Millions of people die every year due to microbiological hazards in the form of food-borne infections caused by unsatisfactory handling practices. There are significant nutritional hazards due to the sub-optimal intake of several key nutrients as a result of poverty, ignorance, indifference and misinformation. In this regard, food quality and safety are a major concern for every food processor. Consumers expect their food to be safe, minimally processed, additive-free and fresh. To meet the growing demands of the consumers for safe and healthy foods, the criteria for safety and quality have to be taken into consideration. Therefore, while developing a new processed food, linkage among R&D organisations, producers and processors should be considered to improve the safety and quality of the processed foods. Although food additives are essential to increase the food productivity in terms of increased shelf-life, quality, nutritive value, convenience and economy, it is necessary to consider if the food additives are safe and how the consumer can be protected from unsafe additives.

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The author is the Associate Professor, Department of Agricultural Engineering, School of Technology, Assam University.