2 Colourings for the food industry – Synthetic colours

Dhinal Patel

5.1 Introduction

Colour is an important feature of food, and consumers often associate it with quality, taste, and flavor. Colourants were used for centuries to improve the appearances of foods, cosmetics, and clothing. Until the 19th century, the colourants used were of natural origin like henna for hair dying or saffron for providing colour and flavor to food. During the 19th century, inorganic colour compounds such as copper sulfate and red lead were used to colour foods, from tea leaves to cheese. At the same time, the rapid development of chemical synthesis led to the industrial production of a large number of organic synthetic colourants. More than 80 synthetic colourants were available, mostly derived from coal tar and petroleum, and some were used as food additives without proper safety evaluations. Several reported health problems, intoxications, and even deaths were related to the consumption of foods containing synthetic colourants.

Despite the new orientation toward utilization of natural compounds, synthetic colourants are still used as food additives. Synthetic colourants are easy to produce, stable, less expensive, and have better colouring properties than natural colourants. Still, synthetic colourants are considered to belong to concern a category that requires the strictest safety evaluations. The use of synthetic colourants is subjected to strict rules.

Synthetic colourants or dyes are attractive to the food industry because they are superior to natural colourants in tinctorial power, consistence of strength, range and brilliance of shade, hue, stability, and ease of application. Synthetic colours provide a larger spectrum of colours. They also have lower prices and greater availability. A various food colorant with colour produced by them are given in Table 1.

Previously, several different colourants were used in foods. However, there has been a decrease in the number of synthetic colourants permitted in many countries. Today, the types of colourants allowed vary greatly among countries, which reflect the different opinions about their toxicity. However, there is a trend toward using fewer synthetic colourants. It is hoped that the trend to international standardization of food colourants will gain momentum. In order to prevent indiscriminate use many countries limit the types, uses, and amounts of colourants permitted in foods. Since different countries allow the use of specific food colourants, it is possible that foodstuffs may be imported into a country that forbids the colouring agent present in the product.

Therefore, methods capable of identifying and quantifying several colours simultaneously are desired in order to verify compliance to regulations. Information on the levels of these compounds in foods is also important to assess where the dietary intake stands compared to the ADI. According to the JECFA (Joint FAO/WHO Expert Committee on Food Additives), each country should verify periodically the dietary intake of colourants, and additives in general, to make sure that intake does not exceed the ADI.

5.2 Synthetic Food Colourants and Their Uses as Food Additives

A various synthetic food colourants and their possible uses in food matrix as food additives are summarized below.

Table 2: Synthetic Food Colourants and Their Uses as Food Additives

ADI = acceptable daily intake, estimate of amount of a substance in food or drinking water, expressed as mg/kg body weight, that can be ingested daily over a lifetime without appreciable risk (weight of standard human = 60 kg); bw = body weight.

5.3 Synthetic Colour and Health

Food colours are being used in beverages, desserts, jams, jellies, sauces, pickles, cosmetics, toothpaste, etc. In addition, medicines, including tablets, capsules and syrups are dyed with food colours. Many of the food industries and other related companies as well as restaurants have relied on colourants in order to sell their products. However, there is a question on the safety and nature of colourants which have been used for these purposes.

Numerous studies have demonstrated the dangers of artificial colourants in food, which include the possibility of onset of attention deficit disorder (ADD), inhibition of the immune system, hyperactivity and allergic reactions. In addition, the use of non-permitted colours or overindulgence of permitted colours may also cause thyroid tumours, urticaria (hives) dermatitis, asthma, nasal congestion, abdominal pain, nausea, eczema, liver and kidney damage and cancer.

In view of the above, several food colourants have been banned in developed countries due to their toxicity observations on experimental animals. Table 3 shows some of the widely used synthetic colourants and their toxic effects.

Table 3: Some of the routinely using food colourants and their effects

5.4 Synthetic Food Colourants and their Application as Food Additives suggested by FSSA (India)

Synthetic food colourants and their possible food application in India with usage limit (singly or in combination) suggested by Food Safety and Standard Authority (India) are summarized in Table 4.

Table 4: Synthetic Food Colourants and their Application as Food Additives suggested by FSSA (India)

Interesting Facts

1  Pliny and Elder described the use of artificial colorants in wine in 1500 BC.

2  An added colour in foods dates back at least 1500 BC when Egyptians were colouring their candies.

3  The first human-made (synthetic) organic dye, mauveine, was discovered serendipitously by William Henry Perkin in 1856.