In this article we will discuss about:- 1. Introduction to Food Additives 2. Classification of Food Additives 3. Food-Borne Molds and Mycotoxins (Food Contaminants) 4. Testing of Food Additives.
Introduction to Food Additives:
Food additives have acquired a social acceptance in the processing and preservation in order to maintain the taste and quality of food products. These additives have now got legal and scientific sanctions because, without changing the nutritional value of the food, they keep the quality, stability and appearance of food in good order. The perishable foods which otherwise go waste are generally saved due to these additives within check the microbial development and quick oxidation, thus reducing the food wastage.
An additive is a substance not normally present in the food in question and which is added either deliberately or incidentally in order to improve the quality or to preserve the food. In other words, food additives are a group of substances which are directly ingested by humans along with food-items or food product.
Actually, naturally-occurring substances are not necessarily non-toxic, for example- the causation of lathyrism, a serious neurological disease due to ingestion of khesari dal (Lathyrus sativus) is well known and its incidence in endemic form occurs in many parts of India and abroad as well. In India, Lathyrism — which is a crippling disease accompanied by paralysis of the leg muscle — is found to occur in Bihar, U.P. and M.P.
Outside India, it has been reported to occur in Spain, Algeria, at Hyderabad has done a painstaking and splendid piece of work to remove toxic factors from khesari dal and has evolved ways and means to remove toxic factors from this seed. Lathyrogens bring about alterations in collagen, elastin and mucopolysaccharides of connective tissue.
The existence of harmful fish toxins has been known for centuries. Teraodontoxin, the active principle of puffer fish, and saxitoxin from muscles are two of the best-known fish toxins. Vegetable cooking fat may contain 5 to 20 ppb of carcinogenic polycyclic aromatic hydrocarbons including benzopyrene.
The whisky drinker suffers in additions to benzopyrene consumption from the barley used in the manufacture of Scotch whisky. Most pulses, legumes and oil seeds including soyabeans that we eat contain various types of antitryptic factors, hemagglutinin or hemolysins and other growth- inhibitory substances. Unless they are adequately processed and detoxified they will be deleterious to human health.
A number of vegetables, especially the Brassica family and soyabean, contain goitrogens. In recent years many goitrogenous compounds in foodstuffs, for example crambe seed meal, have been detoxified by treatment with gaseous ammonia. It is well known that tapioca contains cyanogenic glycosides and steam treatment is necessary to remove these compounds. Peanut meal contains aflatoxin, which is one of most the carcinogenic compounds known today.
Recently the Central Food Technical Research Institute, Mysore, has evolved methods of detoxification of aflatoxin containing meal by treatment with hydrogen peroxide under alkaline conditions. Unfortunately, this treatment may also affect the nutritive value of the meal to some extent.
Those of us with vegetarian tendencies will be depressed to learn that the greens we collect from the market place may add yet another burden of carcinogens. Cabbage and spinach are especially rich in phenanthrene and flouranthene. Seed food grains also contain variable quantities of polycyclic aromatic hydrocarbons with phenanthrene (20 to 100 ppb) as a major constituent.
Coffee has been known to have a mutagenic effect on male larvae of the fruit fly as also in mammalian tissue cultures and has been reported to be hyper-cholestremic. In the gestating rat, caffeine has been reported to cause fetal resorption and abnormalities of various kinds. Certain oxidized and heated fats are known to produce growth retardation, serious pathological changes at the cellular and sub-cellular level, interference with mitochondrial electron transport and alterations in membrane permeability.
Gossypol, present in cottonseed meal, has a growth- retarding effect, especially to non-ruminants subsisting on low protein diets as has been shown by the recent work of Dr. Gopalan at the Indian Nutrition Research Laboratories. Cycad plants grow in many parts of the world and their leaves and seed are eaten by people and animals. These plants contain methylisodimethanol glucosides which, when hydrolysed, behave like their chemical relatives the alkylnitro-samines.
Let us now consider the toxicity of food additives. Table 8.1 shows the list of commonly used food additives. They are additives added to foods with specific technological on nutritional objectives. In addition, food also contains other adventitious chemicals, as those from pesticides, from packaging materials and bacterial and chemical contaminants of various types.
Some of these are listed in Table 8.2:
By and large the additives do not increase the nutritional value of the food, rather they only improve the appearance and sale value and also the texture and flavour. However, commonly used food additives are usually excreted from the body.
Classification of Food Additives:
The food additives may be broadly classified in two groups:
A. The incidental or indirect additives.
B. The intentional or direct additives.
However, a third group, i.e., naturally occurring additives, may result from processing conditions, metabolic reactions and unanticipated chemical combinations. These include safrole and related compounds and contaminants as aflatoxins.
A. Incidental or Indirect Additives:
A food may contain minute traces of a chemical as a result of contact with a substance used in its production, processing or packing. Since its presence serves no useful purpose in the final food product, such a chemical may be considered to be an incidental additive, e.g., food may pick up material from a wrapper or a container, either by dissolving it out or by abrasion from the container into the food. Detergents used for cleaning dishes or food equipments could be such an incidental source.
Of greatest concern are the pesticides which are used in crop production in order to avoid destruction by insects, nematodes, viruses, fungi or other plants peril. Residues of some of these pesticides sometimes may be present on fruits and vegetables even after careful washing. It is self-evident that these chemicals are toxic to some forms of life or they would not have their protective properties for the crop.
Just what hazard they cause to man is a fundamental question. Since the minimum lethal dose of these chemicals for various species of animals is well- known, the products must be used according to specified concentrations. More difficult to determine is the effect of built-up in the body when foods that contain such residues are eaten day after day for long periods of time- even a lifetime.
Toxicological studies on animals throughout their life cycles, including the effects on reproduction and the next generation, are continuously being conducted to minimize such hazards.
Chemicals are intentionally added to foods by the processor in order to enhance the quality of a food such as texture, colour, flavour, nutritive value, or keeping properties to gain better consumer- acceptance.
The intentional additives frequently used can be classified depending on their nature, composition and quality of preservation required:
4. Flavouring agents
5. Colour and preservatives
6. Artificial Sweetening Agents:
(b) Urea derivatives.
The warm climate, temperature and humidity are such variable factors that they boost microbial infections to contaminate the food which, in due course, gets oxidized. The oxidation of food material makes the food unfit for human consumption. The dairy products such as cheese, butter, oils and fats etc. start stinking if exposed to air for a longer period.
To check or reduce the oxidation of these food products, chemical antioxidants are used, of course, with following restrictions:
(a) Such chemicals must be incorporated by the foodstuff and also must not tend any flavour of their own or the colour even during long storage.
(b) It must be fairly cheap and also active even at low concentrations. Only a little quantity of the antioxidants should be mixed with a diluting agent facilitating its proper and uniform mixing without affecting the food texture.
Not more than often, the antioxidants are also mixed with those agents which enhance their action and such substances are known as “synergists”, though they have no or very little activity and only catalyse the action of antioxidant e.g., citric acid.
The natural antioxidants which are used in checking the oxidation of animal fats are oils of soyabean, rice, palm, peanut, olive, cotton seed, coffee etc. Apart from this, certain spices and other natural products — e.g., oxalic, succinic, citric, malic, tartaric and amino acids like cystein, glycine and leucine or amides and proteins — are also used as antioxidants in food preservation.
The commonly used antioxidants by food industries — butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT) and propyl gallate — been found to be the cheapest and best. The aforesaid antioxidants are frequently used to preserve chicken fat, meats, fishes, baked and fried food etc.
To accelerate the process of emulsification certain emulsifying agents are used to boost the desired emulsification. The most commonly used agents are glycerides of fatty acids and their esters, stearic acid, lecithin, and brominated vegetable oils. These agents, however, dilute the consistency of the products and thus, Agar, Gelatin, Pectin, Calcium, Sodium acetate and various starches are used to thicken food products as they possess the affinity with water.
Most harmless and without any toxic affect — the enzymes have been found to play an important role in food preservation and are supposed to be the best commercially available agents. These are amylases, proteases, lipases, pectinases etc.
It is known to all of us that amylases hydrolyses starch and this reaction has been adopted by those engaged in the syrup production from various types of starches. Likewise, various fruit juices are also treated with peptide enzymes for clearing and thereby reducing the viscosity, it also helps storage (wine and soft drinks).
The protein hydrolyzing enzymes have also been successfully picked up in dairy products e.g., cheese manufacturing and also in the preparation of bread and wines etc. Those who consume meat use raw papaya for meat tenderisation while cooking on large scale to make the meat soft and easily digestible. The animals are given intravenous injection of proteolytic enzyme before slaughter so that the enzymes may reach uniformly in each and every part of the body making the flesh soft and tender.
Since these additives are cheap and almost harmless, they are thought to be good ones.
The specifically desired flavour and taste is the first and foremost prerequisite of the food products to attract large number of consumers. In order to improve the taste and increase or decrease the natural flavour of food, the agents which are used are known as seasoners, enhancers, potentiators and flavour integers.
Since long, scents and aromatic oils are being extracted from the leaves, flowers, fruits, barks and seeds of various aromatic plants. The most commonly used odorous plants are orange, lemon, grapes, rose, kewara, khas, vanilla etc. Even in the common houses pickles are made — a good number of raw spices are added to it to increase the taste and aroma.
Apart from vegetative plant materials a good number of comparatively stronger synthetic flavour boosters have also been synthesized. However, such chemicals are used in very small quantity (not more than 300 ppm) yet they have been found quite effective and also easier in mixing. They are usually some acids along with sugar or certain salts and chemicals viz., Di-sodium 5′-inosinate and Di-sodium 5′ quanylate (intensifiers).
However, quite safe and most commonly used natural vegetable aromatic agents are coriander, ginger, garlic, onion, clove, cardamom, saffron, tejpatta etc. These are freely used in our kitchens and houses without any toxic risk. Some of the fruits like mangoes, melon, banana etc. make other substances aromatic.
Colours have been found to be one of the important attractants in the finished food products. Therefore, colours and preservatives are freely added in a variety of edibles e.g., ice cream, sweets, candy, biscuits, soft and alcoholic drinks etc. Besides dairy, confectioneries and beverages, even the pulse like arhar (Cajanus cajan), masoor etc. are also coloured for an attractive food and consequently increased sale (Phool Chap Dal).
Though only a limited number of colours are approved for colouring the food yet people utilize most randomly even the prohibited ones. The colours which are permitted are either of plant origin or synthetic. Some of the permitted colours are Erythrosine, Ponceau 4 R (red), Sunset yellow, Indigo, Carmine, Fast green, Amarnth etc. The permitted colours are either added to some of the edibles e.g., aerated drinks, sauce, jams, syrups etc., or in good number of medicines.
However, since the colours (synthetic) are not quite safe, their doses should be carefully watched and monitored because they cause toxicity in animals. The excess use of some of these colours may cause diarrhea, lowering of RBC count (Ponceau), cholesterol dis-balance, growth retardation etc.
A higher concentration of amaranth has been reported to be carcinogenic, reduces fertility, induces abortion and fetal deformities. The ill-effect of most of the colours is because they do not decompose during digestion. Therefore, colours must be used with caution and care should be taken to restrict to the permitted ratio.
But it is most alarming that most of the sweetmeat shops use certain non-permitted dyes e.g., mentil yellow, auromine, orange II, rhodamine B, congo red, malachite green and methylene violet etc. which are highly toxic and cause irreparable harm to some of the most vital body organs e.g., kidney, spleen, liver, heart, eyes.
The most commonly used natural sweetening agent is sugar (C12H22O11) and is manufactured from sugarcane, palm, sugar beet, pineapple juice etc. In addition to sucrose, other natural sweeteners are glucose, fructose, maltose, lactose etc. But since these sugars are costlier, the industrialists use certain synthetic chemical sweeteners which are, on one hand, cheaper, and, on the other hand, 100 times sweeter than sugar. These chemical sweeteners are the compounds of amides, imides, nitrites, oximes, ureas and nitroaniline groups. Though they are excreted through urine they exert extra pressure on kidneys.
The most commonly used sweetening agents are:
This is a by-product of coal-tar distillation and was developed during World War II (1939-45) by Germans and is chemically called o-sulphobenzimide. It is about 700 times more sweet then natural sucrose. Since this chemical has obtained universal acceptance it is widely used in beverages and cold drinks, toothpastes and several such products. Like other food- additives, saccharin has low acute toxicity in experimental animals. However, it may produce bladder tumors in rats.
(b) Urea Derivative:
Its commercial name is Dulcine and the chemical name is p-phenetyl. It is 300 times sweeter than sugar.
Besides, there are many more such chemicals in commercial use but they are not as safe as saccharin. These compounds have been reported to be toxic and cause damage to kidney, produce liver tumour and several more side-effects.
Molds are well-known to humans for centuries in the production of foods and have provided a number of fungal metabolites with salient medicinal applications. On the other hand, they may produce various other metabolites which may produce severe adverse health effect. Important among these are aflatoxins and trichothecenes.
Other mycotoxins and subgroups are listed in Table 8.9:
Actually, aflatoxins are some of the most toxic and carcinogenic substances known.
The comparative carcinogenic properties of aflatoxins with other well-known carcinogens are illustrated in Table 8.10:
Other Contaminants of Food (Metals, Pesticides and Antibiotics):
Various metals, pesticides, antibiotics etc. accidently or intentionally may contaminate the food stuffs as summarized in Table 8.11:
Testing of Food Additives:
Unlike drugs, food additives are not used for their specific biological additives but are used for their specific technological effects and to ensure the maintenance of the natural quality of food. With food additives the hazard, if any, is more likely long- term rather than acute.
The problem of testing food toxicity is much more complicated than that of testing drug toxicity. The composition of the food additives, the conditions and extent of usage and their biological properties — all factors have to be taken into account in evaluating the possible hazard or ensuring the safety in use of food additives.
Apart from chemical and physical specifications the main headings under which information should be sought are:
1. Acute toxicity data by oral and by injection in rats, mice and one additional species.
2. Short term studies (feeding for 90 days). In rat or mice and one additional species — usually for a period of 10% of the life span. In this case a 1,000-fold margin of safety on non-effective levels in animals has been suggested in humans.
3. Long term (usually 2 years) tests which include studies on toxicity, with histopathological data, fertility and carcinogenicity. In this case a 100- fold margin of safely has been suggested in humans over non-effective levels in animals.
4. Metabolic effects on enzyme levels etc. Estimation of serum enzyme concentrations undoubtedly gives an excellent indication of tissue abnormalities and the acute effects of many hepatotoxic compounds. Elevation in urine enzyme levels can give some indications of kidney damage. These tests require sophisticated technologies and, apart from animal-house facilities, a good deal of inter-disciplinary collaboration between biochemists, physiologists, histochemists, electron microscopists, pharmacologists, and oncologists, in addition to analytical chemists, is necessary.