The idea is simple enough: Food colours are added to foods to change their colour and appearance – often to help consumers find them more appealing. Colouring compounds can be natural compounds, man-made (or synthetic) dyes that have been shown to be safe to add to foods, or full extracts of foods or herbs that are added for their colour properties.
Experts have long known that colour plays a crucial role in the taste and perception of food. Alongside ﬂavour and texture, colour is considered by food scientists to be a major quality factor of food.
“If you don’t have the colour right, I think you can forget about the other two,” warned Jack Francis from the University of Massachusetts, in a recent review of food colours in Comprehensive Reviews in Food Science and Food Safety.
“If it isn’t the colour you expect it to be, you don’t like it,” he said.
Business manager at Naturex Amandine de Santi echoes such suggestions, noting that everybody is sensitive to colour because “it stimulates our appetite and can enhance flavours.”
“If you give somebody a strawberry flavoured candy sweet, but it was coloured green, they would find it very difficult to distinguish the flavour of the candy,” she said. “By adding a red, people associate that with the strawberry flavour and it helps to enhance the flavour.”
She added that food processing can affect the natural colour of food, so colours can also be used to bring back that colour.
However the relationship between colour and consumer perception does not stop with taste or liking, she says. It can guide consumers’ judgements and purchase decisions too by gently influencing what they believe the product may contain.
For example, she noted that an intense colour in beverages will always give the impression that it contains sugar, while lighter beverages are perceived to be lower in sugar.
This sort of knowledge is what helps manufacturers appeal to their target consumers.
Instinctive and ingrained?
Writing in his review on food colours, Adam Burrows notes that these sorts of reactions to the appearance of food are often instinctive, and have been ingrained in humans through millennia of habit.
He says when early humans searched for food, they learned to avoid toxic or spoiled objects by their colour.
“Colour was the most readily accessible clue, and such inedible items are often blue, black, or purple,” Burrows wrote.
“Blue has long been one of the most popular colours in human decoration, but it is known to be one of the least appetising.”
“Studies have shown that people actually lose appetite when fed food dyed blue,” he said, adding that many food manufacturers have dealt with this limitation of their palettes in an ingenious way:
“They have kept blue away from ‘real’ foods, and relegated it to the realm of ‘fun’: candy, kids’ cereals, and sports drinks.”
A colourful history
“Colours have been added to foods for centuries,” said de Santi.
Indeed, archaeologists believe food colours likely emerged around 1,500 BC – with the use of saffron as a colourant mentioned in Homer’s Iliad, while in 400 BC Pliny the Elder remarked that wines were artiﬁcially coloured.
The use of food colouring in the wider sense is believed to date at least back to early Roman times, where it is known that people used saffron, various flowers, carrots, mulberries, pomegranates, and beets to add colour to foods.
From the 18th and 19th century onwards non-natural food colourants started to become popular, with food colouring compounds including copper sulphate, mercuric sulphide, copper carbonate, copper arsenite, vermillion, and black lead.
The first fully synthetic food colour, mauveine, was prepared in 1856 by oxidization of aniline.
An end in sight?
Burrows said that given the nature of colouring compounds until very recently, current worries about ‘synthetic’ colours need to be put into perspective.
“It is hard to believe that only a century ago, our ancestors were eating food dyed with highly toxic colour additives,” said Burrows. “From that auspicious starting point, we have come to a time where a food colourant with a 1 in 19 billion chance of causing cancer is legally considered too dangerous.”
“What we use to dye our foods and how we regulate it may continue to change,” he said, “but there is no end in sight to the timeless practice of colouring our food.”