Micronutrients as food additives

Micronutrients have many functions in the human organism. For example, they are needed to make macromolecules or as cofactors for essential enzymatic reactions. Micronutrient functions are based on their biochemical properties and are utilized in food technology. Many industrially processed foods contain additives that are in fact natural or nature-identical micronutrients. Their purpose is to improve the consistency of the food and to give it certain characteristics. Additives are selected based on their primary function in the finished food product. Micronutrients are usually used as antioxidants – to prevent oxidative processes that impair food quality – and as coloring agents to compensate for color lost during processing. Additives are generally labeled with E numbers. The use of additives in food is only permitted if it is technologically necessary, if they have been investigated and found to be harmless, and have passed inspection by the food safety authorities.

The permitted amounts of most food additives are limited – they usually comprise less than 0.1% of the food to which they are added. The greatest permitted amount is co-determined by the ADI (Acceptable Daily Intake) value of a specific substance. This is the amount that a person could consume every day of their life without damaging their health. Whether or not a substance is regarded as an additive depends on its primary purpose. So if, for instance, vitamins are used for the purpose of improving the nutritional value of a food, they are considered to be ingredients. However, if they are used to give color, or for other technological purposes, such as influencing stability or sensory qualities (appearance,  aroma, odor), for example as an antioxidant, they are included among the additives. Authorities like the FAO/WHO and EFSA are responsible for evaluating the safety of food additives. Information about the global legal regulations for food additives can be found on the website of the International Food Additive Database, www.foodadditivedatabase.com.

Use of micronutrients as

Antioxidant agents

Many foods are susceptible to oxidative processes when they are exposed to oxygen and/or light (for ex- ample in connection with the plant chlorophyll). Thus, apples or potatoes can be prevented from going brown when cut by being immersed in lemon juice. The lemon juice not only improves the aroma but contains ascorbic acid that acts as an antioxidant, and the citric acid inhibits the enzymes responsible for the brown color. Antioxidants are useful preservatives, preserving food fragrance, flavor and color and making it possible to keep and enjoy food for longer. The most important antioxidants – the ones which stop the fats in food becoming rancid and prevent the destruction of vitamins and aromatic substances that deteriorate on exposure to air – are tocopherols (vitamin E) and ascorbic acid (vitamin C). Both these micronutrients can come from natural sources, but are more often synthetically manufactured, with a nature-identical structure (1). All the antioxidants added to foods have been classed as Generally Recognized As Safe (GRAS) by the Food and Drug Administration (FDA) of the USA (2). In Europe, Regulation (EU) No. 1129/2011 regulates all categories of additives as regards substance types and their conditions of use.

Vitamin C (L-ascorbic acid / E 300) and its ascorbates (sodium-L-ascorbate / E 301; calcium-L-ascorbate /
E 302) function as water-soluble antioxidants. They are used to prevent free oxygen radicals from causing damage in the aqueous compartments of cells and tissues of animal or plant origin or in the aqueous phases of foods. By combating oxidative processes of degradation, ascorbic acid and ascorbates preserve the color and aroma of products (3). Hence cooked sausage and salami, for instance, keep their color for a while after opening. They do not immediately become brown and therefore remain appetizing for longer. The use of L-ascorbic acid is common in meat products, where they fulfill a specific function in a particular group of pro- ducts, i.e. cured meat, ham or cured sausage (4). Curing is a process that has long been used to preserve meat products. Adding nitrites (in the form of nitrite salt) or nitrates as curing agents not only preserves the product but lends it its specific red color and typical aroma. The process of color development is achieved when the muscle pigment myoglobin combines with nitric oxide formed from the nitrite. The added ascorbic acid encourages nitric oxide formation and thus ensures optimal conversion of the nitrite. This has benefits for consumers and food producers: less added nitrite is needed for curing, the residual nitrite concentration in the meat is lower, the time required for color development is shorter and the color achieved is more uniform and more stable. In addition, ascorbic acid inhibits the occurrence of nitrosamines, which are formed through the reaction of nitrite with amines, especially at high temperatures, e.g. when grilling meat.  They are suspected of being carcinogenic. The formation of nitrosamines during meat preparation can be inhibited by adding vitamin C (and vitamin E) (5). Depending on the recipe and technology used, between 200 and 600 mg/kg of ascorbic acid is added to meat products.

As antioxidants, ascorbic acid and ascorbates also protect the pigments and aromatic substances in foods against degradation. They are added to a number of industrially produced products, including fish, vegetable and fruit preparations, and beverages. Beverages and also jellies sold in transparent containers and thus exposed to light can become a brownish color if not sufficiently protected against oxidation (6). The additives must always be listed in the declaration of ingredients for the product.

Vitamin C plays a specific role as a flour improver, especially for wheat flour (7), to which tiny amounts of ascorbic acid are added (1–2 grams per 100 kg). The advantage: after grain has been milled the flour nor- mally needs to age for the present enzymes (amylases) to break starch down into sugar and improve the baking qualities of the flour. Ascorbic acid acts as an oxidant in association with amylases and accelerates the aging of flour,, which then takes a few days instead of several weeks. Moreover, ascorbic acid stabilizes the gluten structure of the milled grain by binding oxygen and reacting with it to form dehydroascorbic acid. In this way vitamin C makes the dough stiffer and increases the volume of finished products because more of the carbon dioxide produced by the yeast is retained in the dough. Since vitamin C is not heat-stable it is destroyed during the baking process (8).

Tocopherols (vitamin E / E 306), with their pure representatives alpha-tocopherol (E 307), gamma-tocopherol (E 308) and delta-tocopherol (E 309), are fat-soluble antioxidants and can protect the fatty acids in cells and tissues of animal and plant origin against damage by oxidative oxygen molecules. Oxidized vitamin E is par- tially regenerated by vitamin C. Tocopherol activity is particularly important in reducing the oxidation of fats and oils or products containing fats (9). Their addition can delay the occurrence of the final stage of auto- oxidation, the rancidity that is noticeable because of the unpleasant smell or taste it causes, and associated color changes.

Tocopherols are primarily used for stabilizing animal fats in processed foods. Plant oils with high concent- rations of oxidizable polyunsaturated fatty acids, in contrast, naturally contain substantial amounts of toco- pherols, so that if required other antioxidants, like ascorbyl palmitate (E 304) improve stability. Up to a total of 0.5 milligram per gram of tocopherol may be added to oils like margarine that are naturally low in them (10). In pre-packed meat, antioxidants such as vitamins C and E improve stability and long-term quality of the goods. These, too, are declared on the label. The protective effect of vitamin E on polyunsaturated fatty acids is of benefit even before animals are slaughtered: if vitamin E is added to the rations of cattle, pigs and poultry, the quality of the meat (color, aroma, tenderness) is maintained for longer after slaughter (11, 12).

Coloring agents

Foods with vivid colors – e.g. greens, yellows, orange or red – are associated in the minds of consumers with positive qualities like flavor and health, and can stimulate the appetite. In food production, coloring agents are added primarily to compensate for the loss of color (bleaching) sometimes caused by processing. The use of natural coloring agents is increasingly common, encouraged by the rising demand among consumers for more natural foods coupled with a growing awareness of food ingredients. The statement “contains no artificial colors” is now regarded by consumers as a significant sign of quality products without health risks (13). This has been reinforced by research appearing to indicate that purely artificial azo dyes, which do not occur in nature, could lead to attention deficit and hyperactivity (ADHD) in children (14). The authorities, too, have reacted. Since the summer of 2010, in the European Union foods containing the azo dyes Tartrazine
(E 102), Sunset Yellow FCF (E 110), Carmoisine (E 122), Allura Red AC (E 129) or Ponceau 4R (E 124) must be labeled with the warning “May have an adverse effect on activity and attention in children.” Azo dyes are also suspected of triggering allergies (15).

The attractive yellow/orange/red coloring agents are especially popular for coloring foods (e.g. beverages, cakes, pastries; dairy products and sweets). In particular the fat-soluble carotenoids – like beta-carotene (E 160a), lycopene (E 160d) and lutein (E 161b) – offer a broad range of colors for coloring foods in the yellow/orange/red spectrum. Natural beta-carotene is obtained mainly from carrots and red palm oil or from certain microorganisms. However, nature-identical (synthetic) manufacturing is most widespread in the marketplace. The coloring agent is commonly used in butter, margarine, cheese, mayonnaise, ice cream and deserts. Manufacturers will always use as little beta-carotene as necessary, since any over-coloring will be rejected by the consumer and costs money. Beta-carotene is added to beverages for two reasons: one to improve the nutritional content of the product (as provitamin A), and two as a coloring agent.  The consumer can always determine the primary purpose from the list of ingredients (16, 17).

Pure lycopene, the red pigment of the tomato, is used comparatively rarely, since good coloring effects can be achieved easily using tomato concentrates as coloring foods. These are used for savory products like sauces, fish and shellfish products, and aromatized processed cheese, as well as meat and fish substitutes. Lutein (which may also be declared as xanthophyll in the list of ingredients) is obtained for use as a yellow-orange pigment in foods mainly from a species of marigold (Tagetes erecta) and used in particular to color baked goods, deserts and sweets (18).

Another alternative to azo dyes that presents no risk to health is the yellow pigment riboflavin (vitamin B2, E 101) and its derivative riboflavin-5’-phosphate (E 101a). Riboflavin is produced biotechnically through fermentation. It is typically used for instant products, sauces and soups. Riboflavin-5’-phosphate is used in place of riboflavin because of its superior solubility (19, 20).

Further, iron oxides (E 172) are used to color foods. These pigments furnish a palette of colors from yellow to red and brown. They are used to give color to fish and meat pies, ready-made deserts and soups (21).

Other

Some minerals and their derivatives that pose no risk to health are added to foods as preservatives or stabilizers, or as thickeners to increase viscosity and as emulsifiers or separating agents, to give the pro- ducts a longer shelf-life, keep them looking appetizing and reducing caking.

Calcium lactate (E 272) is the salt of lactic acid. It is obtained commercially from starch and molasses. It inhibits the occurrence of yeasts and molds. During the processing of fruit, vegetables and potatoes, calcium lactate can maintain their consistency and also has an antioxidant effect (22). Calcium citrates (E 333) are the calcium salts of citric acid. They are used as buffers to bind metal ions and thus improve the consistency of canned vegetables. Calcium phosphates (E 341) are the salts of phosphoric acid. These bind metal ions and moreover support the effects of antioxidants. Therefore, they are also used to stabilize the consistency of canned vegetables. Calcium phosphates serve as acidity regulators, e.g. in baking powder to improve the baking properties of bread. They are also added to other powders to improve pourability and avoid caking (23, 24). Calcium alginate (E 404) is the calcium salt of the alginic acid obtained from brown algae and is added to foods as a stabilizer and thickener, especially in ice creams and cream products. Calcium oxide
(E 529), also known as quicklime or burnt lime, is used primarily as an acidity regulator in cocoa products and baked goods, as well as in the preparation of natural casings for the manufacture of sausages (25, 26).

Magnesium phosphates (E 343) are the magnesium salts of phosphoric acid. In food they are used pri- marily as emulsifiers for baked goods. They are added to powders to prevent caking and they increase the effectiveness of antioxidants (27, 28). Magnesium (hydroxide) carbonate (E 504), which is the result of the chemical reaction of magnesium and carbon dioxide, is added to foods as an acidity regulator, carrier sub- stance and separating agent, for example for the chemical digestion of cocoa and milk protein, to table water and to common salt (29). Magnesium hydroxide (E 528) can neutralize acids and is used as an acidity regulator – mainly in the manufacture of cheese and canned vegetables. It is often used just as a technical adjuvant, and is no longer detectable in the finished product (29, 30). Magnesium oxide (E 530) occurs after incineration of magnesium carbonate. It has an acid-neutralizing effect, helps chemically digest cocoa and milk protein and acts as an anti-caking agent in powders. In this function it is added to raw cocoa paste, table salt and seasoning salts (29).

Sodium carbonate and its derivatives sodium hydrogen carbonate and sodium sesquicarbonate (E 500) are used as raising agents. These additives release gases that increase the volume of dough. Sodium carbonate is also used as a carrier and acidity regulator in baking powder, chocolate and cocoa products, sour cream butter and table water (30).  Sodium chloride (common salt) has traditionally long been used to preserve food by curing (meat), pickling (fish and vegetables, e.g. herrings, olives, gherkins) or fermenting (sauer- kraut). Since sodium chloride draws water out of food, it combats the growth of microorganisms like bacteria and yeasts that contribute to spoilage, and is therefore antimicrobial (31, 32).