Published: 06/06/2016 - Updated: 03/08/2020
Author: Dra. Loredana Lunadei, PhD
Sometimes our eyes can tell us more than we think, at least this proves to be the case in plant-based foods, which with their wide range of colours, are not only aesthetically appealing and interesting, but they can also indicate what they will provide our body with after giving them a succulent bite. Sometimes they can also act as warnings that allow us to avoid certain foods too. The pigmentation of the skin of fruit and vegetables can be an interesting code, not always universal, but it is worth always examining the “how and why” of things. This knowledge can prove to be useful and fun in the kitchen.
Pigmentation in fruits and vegetables
The first and most widely recognised pigmentation or colour you will come across is green, which comes from chlorophyll, which allows the entire plant kingdom to harness solar energy to carry out the process of photosynthesis that form sugars in plants. We can find examples of this in plants such as lettuce, broccoli, zucchini, celery and a large variety of other fruits and vegetables. Except for a few exceptions, all vegetables have at least one part of their structure which displays this beautiful colour, indicating that there is life on our planet. This pigment is not toxic, although the potential nutritional properties which they can bring us are not completely clear: It is believed to have antioxidant properties and some minerals such as copper, however the truth is that this pigmentation is present in almost all vegetables we eat, so it is almost certain that at some point of the day, it will be incorporated into our diet. However, green is not always a good sign, as I mentioned earlier sometimes pigmentations are warnings. This is the case of potatoes, which are tubers that grow underground and so have no reason to produce this pigment. Exposing potatoes to the sun usually constitutes “damaged produce” as the green pigmentation indicates the presence of some toxins known as glycoalkaloids that can be dangerous.
Carotenoids: Red and yellow pigments
Another family of pigmentation is the carotenoids, which produce beautiful yellow and orange vegetables such as carrots or bell peppers. Have you ever eaten many of them and the palms of your hands have turned orange? This is the good effect of this pigment running through your blood and the following fruit and vegetables contain it: Peppers, watermelons, tomatoes, corn and cherries. They present these famous pigmentations, which are also indicative of some kind of vitamin A content, which is produced in our gut by some carotenoids when consumed, not because the vegetables have the vitamin, but rather they just give us the raw material to manufacture it in our bodies. Of course these vitamins also help to take care of our vision, as well as maintain organs such as the heart and kidneys and keep our immune system in shape.
However, not all yellow and red tones provide carotenoids: Another group of pigments known as betaines found in a smaller vegetable group include beetroot or sugar beets, which many of us will notice after having eaten a lot of either, they have a significant effect on the colour of our urine. Betaines have antioxidant properties that protect against oxidation or ageing of our body, they reduce levels of homocysteine which we may have in our bodies and perhaps poses a risk to our heart. Betaines apparently also help to reduce the accumulation of fat in our livers. Chard, broccoli, amaranth and spinach are other vegetables that can be a source of betaine pigmentation.
Anthocyanins and anthoxanthins
Other red, purple pigmentations are known as Anthocyanins, and anthoxanthins are responsible for yellows. The main function of these pigments is to generate messages through flowers and fruits, which repel or attract potential animals interested in them. Therefore, we cannot resist trying a cranberry or different varieties of blackberries as they are programmed to say “eat me”, which in the case of fruits, allows people and birds to eat them and later disperse their seeds. With regard to flowers, in a similar vein they have to draw the attention of pollinators, such as bees. The consumption of anthocyanins in our food also provides antioxidants and potential benefits in preventing cancer. Fruits which contain these pigments are berries in general, all blackberries, eggplant and grapes.
As you can see, the colours of a plant or fruit/vegetable can also be a nutritional indicative, however we must also take note of the rest of their components because here we only focus on these components of the plant, but these are very complex mixtures with many interesting chemical groups, of which many remain to be discovered. We must also take into account that plants do not have a single pigment and can, in fact, combine several of them, such as broccoli (chlorophyll and betaines). I hope this short text will contribute to you finding your vegetables to be more appealing or interesting. Please do not forget to share what you like about them or anything you would like to know about them in the comments section.
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