The debate on food additives has been going on for a very long time, probably since they were added to food to better preserve it or to make it more appealing to the consumer. The debate on dyes fits into this perspective and especially on the diatribe between synthetic and natural ones. It also has been discovered that most of what we eat would not seem appealing if it were not colored; so much so that many experts in the sector have indicated food colorants as "cosmetics for food".
Indeed, this is precisely their purpose: coloring additives strengthen the colors already present in food and ensure their uniformity. Natural colorants have therefore always been part of our diet, but in recent decades the demand has increased considerably to ensure a wider variety of colors and shades that are more stable and livelier. This has been developing with the advent of processed foods which, perhaps more than others, need to be "revived" from the point of view of color. Refrigeration, canning, dehydration, smoking, bottling and exposure to light, air, humidity and extreme temperatures tend, in fact, to heavily alter the natural color. Another huge problem concerns the indiscriminate use of these additives. It was relatively easy for the unscrupulous to use dangerous or intentionally deceptive colors to hide poor quality and make the imitation of a product certainly not as fresh or as real.
Starting from the early 1900s, and over the course of the next fifty years, derivatives of organic dyes synthesized starting from chemical compounds (such as aniline) have been developed, since it was possible in this way to represent each color and nuance of the rainbow, and many have been used to color food without thinking or testing their safety. The significant toxicity of many of the early aniline and coal tar colors prompted lawmakers to examine exactly what was used to color food. This helped pave the way for the use of natural colorants. Indeed, in recent years there has been an increase in the use of natural colorants which, since 2011, have overtaken synthetic ones in new products launched on the market and now account for 40% of those used in the food world. These additives are increasingly used for various reasons. First of all, for the image of greater harmlessness and genuineness, but also for more substantial reasons, such as physiological effects and the possibility of use in some cases a higher amount. Some “ecological” reasons are less important than in other fields, such as the availability of natural sources: the amount of raw materials needed for the synthesis of artificial food colors represents a negligible part in the world of synthetic chemical products. Furthermore, new scientific findings have made it possible to use some products, previously considered only colorants, also for their nutritional properties. For this reason, natural extracts, which coloring characteristics are associated with aromatic and nutritional properties, are increasingly used in food.
But what are the categories of natural colorants currently most used?
Carotenoids (E160-E161). These are molecules responsible for the color ranging from deep red (lycopene E161d), yellow (E161) or orange (E160a). Probably the most common carotenoid is beta-carotene (E161a), which is responsible for the bright orange color of sweet potatoes and pumpkins. Since beta-carotene is fat soluble, it is a great choice for coloring dairy products, which typically have a high fat content. For example, beta-carotene is often added to margarine and cheese.
Chlorophyll (E140-E141) is another natural pigment, present in all green plants. This molecule absorbs sunlight and uses its energy to synthesize carbohydrates from carbon dioxide and water (photosynthesis, the basic process of life on Earth). Mint or lime-flavored foods, such as candy and ice cream, are sometimes colored with chlorophyll.
The best natural source for deep purple and blue colors are anthocyanins (E163). Grapes, blueberries and other berries owe their rich color to these organic compounds. Unlike beta-carotene, anthocyanins, which form a class of compounds rather than a single chemical compound, are soluble in water; therefore, they may be used to color water-based products. Blue corn chips, brightly colored sodas, and jellies are often dyed with anthocyanins. More than 500 different anthocyanins have been isolated from plants. They are all based on a single basic central structure, the flavilium ion. This ion contains three rings with six carbon atoms, as well as many hydroxyl groups (–OH) which make the molecule polar and soluble in water.
Another natural food additive is turmeric (E100), which is added to mustard to impart a deep yellow color. Turmeric is obtained from the ground root of a plant that grows in India and is commonly used as a spice in Indian food. Many US food companies are using turmeric and other natural spices to color their products. Turmeric is also a great acid/base indicator.
Betanin (E162) or beetroot red and various types of liquid or vaporized concentrated juices on powdered supports are obtained from red beetroot. It is very sensitive to heat (over 70 °C it is degraded) and changes according to the pH level. It is an inexpensive dye widely used in industrial ice cream and fresh sausages or hamburgers.
Obviously, not all natural colorants are of vegetable origin. Indeed, one of the most controversial colorants of all time is the one from an animal origin, not so much for food safety issues but for ethical and social ones. Let's consider carmine red; it is an extract derived from a species of insect known as cochineal. For centuries, the Aztecs have used these insects to dye fabrics a deep red color. If you squeeze 70,000 of these insects, you can extract half a kilo of a deep red dye, called carminic acid (E120). This dye is safe to ingest, so it found its way into a variety of food and cosmetic products that called for a red color. However, the thought of eating insects is not appealing to some people and unethical to vegans and vegetarians.
To finish this list with colors-non-colors there are also white (inorganic pigments such as calcium carbonate E170 and titanium dioxide E171) and black (vegetable carbon E153).
Much research is currently underway aimed at extracting natural dyes from food industry waste and by-products. This choice is part of a virtuous system that had its maximum expression in the rules package approved in 2018 by the European Union, also known as Circular Economy.