Food Pigments: Colours Unveiled

By: Tini Thangjam
We consume various foods everyday of different shapes and colour. Specially fruits and vegetables have an array of colours which are known as pigments. These compounds are the reason for a medley of shades present in foods. They can range from bright reds to cool purples. Carotenoids, anthocyanins, anthoxanthins, chlorophylls and betalins are the pigments primarily present in foods. These pigments are naturally present in the cells and tissues of plants. Today we will be discussing about each of the pigments mentioned.
Starting with the most common: chlorophylls. I am sure many have heard the word chlorophylls. These are water insoluble compounds present in most green leafy vegetables and mostly throughout the whole plant. They are the main pigment responsible for photosynthesis in plants. They are what gives the plants green colour. The two functional pigments in photosynthesis of plants are chlorophyll a which imparts blue-green colour and chlorophyll b which imparts yellow-green colour. When the green vegetables are cooked in boiling water due to the translucency of tissue the green colour becomes brighter. If it is cooked for a prolong period it turns into olive green. This pigment is sensitive to heat and freezing is the best choice for retaining chlorophyll.
Next are carotenoids. They are also water insoluble pigments which is responsible for yellow, orange and red colours. They are present is tomatoes, carrots, yellow corn, etc. Carotenoids present in plants can be further classified to a- carotene, b- carotene, g- carotene, xanthophyll, lycopene and cryptoxanthin. The color of carotene is little affected volume of water, alkali and acid. Among all the carotenoids â- carotene is the one used for the synthesis of vitamin A.
In the red,blue and violet coloured foods there is a water soluble pigment present known as anthocyanin? They occur in cherries, pomegranate and also in our most beloved black rice. These pigments leach out in the cooking water. When they come in contact with iron, aluminium, tin and copper ions they turn into green or stale blue. If any alkali is added it becomes a bluish green shade. Now, these anthocyanins maybe absent in some families and are replaced by other compounds betacyanins and betaxanthins. They are collectively known as betalins. They are water soluble and are present in beet roots. Its colour differs with pH; reddish colour in acidic medium and brownish blue in alkaline medium.
Anthoxanthins are the creamy yellow, creamy white or yellow white pigments. These are water soluble too. They can be colourless or white to yellow depending on the pH level. They are usually whiter in acidic environment and yellow in alkaline conditions. Cauliflower, potato, cabbage bananas, ginger and turnips are some examples which contain anthoxanthins.
Other than these main pigments there are other pigments too which don’t occur as widely. Some examples are, curcumin present in turmeric and annatto derived from seeds of achiote tree providing the yellow to orange colour and used for colouring cheese.
These pigments are not only pleasing to the eye but recently beneficial factors are coming to light. They are usually associated with powerful antioxidative properties, increased cognitive function and preventing neural failure, detoxification, reducing inflammation and many more. It is more than what meets the eye when it comes to pigments of food. They provide visual contrast and help us distinguish between the unripen and ripen, good and the rotten ones too. Colours make food look attractive and appealing to the eyes.
Nowadays in the food industry many are using added colours. These can be sourced naturally and can be made artificially too. Natural food colours are at a disadvantage compared to synthetic food colours in terms of intensity, stability and availability. Although synthetic food colours outweigh the natural ones in many sections, still people are promoting natural colours more as the don’t have the toxic properties. Therefore, establishing a trend to use natural food colours as more and more concerns raise around the synthetic colours. The use of food colours are closely regulated and many have been banned. Metallic colours, vegetable colouring matter, coal tar colours are all banned due to their toxicity and carcinogenic properties. Some may ask why use added colours be it natural or synthethic at all if pigments are already present in the food itself. The answer is most manufacturers use colour to compensate the loss of colour during the processing or cooking, storage or simply to enchance.
It is clearly advisable that one should not consume foods containing synthethic colours. While searching for the beautiful appeal it exhibits one may suffer the effects of its toxicity later in life. Instead, we should eat the fruits and veggies containing all the beneficial pigments and say no to artificial dyes. It is now crystal clear that colours present in foods play a crucial role in visual appeal as well as in imparting health benefits.
(The writer has finished her Bachelors in Food Technology from College of Food Technology CAU, Lamphel, Manipur. The writer can be reached at [email protected])