Nailing down what, exactly, food coloring is made of is often very difficult because of how many options there are. A lot depends on what the coloring is used for &mdash: pigments available to home cooks are often different from those used by manufacturers, for instance, and colors are designed for baked goods and confections are often quite unlike those used for meats, packaged fruits, and so on. In general, though, all food colorings come from two broad sources. Naturally derived colors come from plants, animals, and other organic material. Chemical colors, on the other hand, are often coal or petroleum based, and tend to be mixed to perfection in labs using a lot of artificial processes.
Knowing the specifics of a given coloring’s history is inexact at best. Different countries have different labeling, naming, and identification requirements, which makes it hard to know how to classify certain coloring agents universally. Laws also tend to vary when it comes to what sorts of additives are “safe” to add to foods. Despite these roadblocks, a bit of research can often help uncover at least some basic information — and a few general rules can provide broad guidance.
Most food coloring comes packaged either as a powder or a liquid. Powders are typically a combination of coloring crystals and other preservatives that prevent caking and lengthen potency. These can be added directly to foods as they are being made, but usually require a bit of water to activate them. Liquid versions, on the other hand, already contain water in most cases, though they may also be made up of soluble oil. Both versions tend to be very concentrated, which means that cooks usually need to experiment with how much to add in order to get the right hue.
At one point, all food colorings got their color from natural sources. “Natural” is a broad term, but it usually encompasses anything that is available in nature. Plants, particularly flowers and roots, are very common examples, as are insects, rocks, and certain soil components. The natural world remains a common source of many of today’s commercial colorings and dyes.
The vibrant seeds of the achiote plant are frequently used to make red coloring, for instance, though the juices of elderberries and beets are also popular choices. Pressed poppy leaves and saffron tendrils can be used to create an orange tint, and yellow often comes from the turmeric spice. Green is usually relatively easy to create, but some common sources are algae and seaweed. Extracts from the indigo plant and the butterfly pea will create a blue color. Browns, blacks, and other "compound" colors are usually made by blending different natural tints together.
One of the biggest problems with plant-based hues is that they often fade over time, and may not be colorfast. What looks bright and vibrant in the bowl may only show up very lightly when mixed with other ingredients. This has led many manufacturers to look for other, more potent natural sources, some of which come from the insect world. A number of scaled insects like beetles can be crushed to release carminic acid, which has a vibrant red color. Tropical bugs have also been used in creating purple shades.
Artificial and Chemical Derivatives
In many cases it is less expensive to create colors synthetically. A number of chemical reactions will release colored byproducts that can be used to tint food in a way that is more potent and longer lasting than natural compounds. The burning of coal tar is one of the easiest ways to create a spectrum of colors that can be manipulated based on temperature and burn time. Tartrazine and erythrosine, both petroleum byproducts, are similarly flexible, and form the base of many different color combinations.
Potency Based on Coloring Type
A lot of what a food coloring contains may also be dependent on its “type,” or basic classification. All pigments can be divided into “lakes” or “dyes.” Lake colors are not oil soluble, and typically tint by dispersion. These are most common in “batch” foods like mass-produced candies, cake mixes, and the coatings for pharmaceutical drugs. Dyes, in contrast, are typically what comes in the bottles of food coloring sold at grocery stores and other specialty markets for home cooks. Dyes are also most common in beverages and baked goods since they tend to dissolve in water. Manufactures typically choose a coloring source that is both efficient and appropriate to the type of product being made.
Health and Safety Concerns
Food safety experts have raised a lot of concerns about coloring agents, natural as well as chemical. Many of the biggest concerns relate to coal tar derivatives, which have been shown to cause asthma and other respiratory problems when consumed in large quantities. Other chemicals used to seal color potency have been linked to certain cancers, heart troubles, and behavioral problems, particularly in children — but again, most studies focus on extended exposure over a prolonged period of time. Researchers tend to agree that limited amounts don’t pose any serious threat, though a lot remains unknown. People prone to allergies or who have particularly sensitive systems often experience bad reactions even from very limited exposure.
Most governments around the world limit the types of substances that can be used in food coloring intended for human consumption. Different countries have different labeling systems for colors, as well as different rules about allowed ingredients. This makes it hard to draw even basic generalizations about what can and cannot be included in food coloring. Regulatory bodies are usually open about their rules, though, and are generally willing to answer a range of consumer questions.