Haunted by colourful fruits & vegetables As if I have never seen this before! I was struck by the vivid colours of the fruits and vegetables we eat while emptying shopping bags into the kitchen’s worktop. I couldn’t resist arranging some for taking pictures. But the taking of the pictures was not to be the end of the story of a rather dull shopping adventure. Things like “COLOURS & PIGMENTS” and words like “WHAT & WHY” kept coming back to my mind for the rest of that afternoon. More often than not, edible fruits and vegetables are shades of one or more of only two of the primary colours; mostly the red and the green. While there are many pure reds and pure greens there is no pure blue fruit or vegetable I could think of. The skin of the aubergines and only a handful of other fruits and vegetables show obvious shift toward the blue side of the colour spectrum. Why no pure blue? I knew that the green colour comes from the chlorophylls and wrongly assumed that the red comes only from the carotenes which are present in all plants. A little search showed me that other chemically unrelated pigments, namely anthocyanines and betacyanins, are responsible for a wide range of reddish colours in the things we commonly eat. Although all plants have carotinoids, its reddish colour is often masked by the greenness of the chlorophylls. The bright red coloured lycopene is an important substance for the biosynthesis of many carotenoids, including betacarotene. However, unlike betacarotene, it does not have Vitamin A activity. There is no doubt that lycopene is the pigment responsible for colours at the red end of the spectrum of some of the fruits and vegetables we eat, including tomatoes, carrots, watermelons, etc. Obviously not all red colours in this range are due to lycopene. Anthocyanins appear to the pigment responsible for other bright red fruits, such as raspberries, strawberries, cherries and plums. They also form the colour base for many fruits and vegetables we do not necessarily recognise (or name) as being as red. The blueberries skin in not blue but purple, the blackcurrants are not black but dark reddish brown. The same applies to the some varieties of plums, the black grapes, the aubergines, the red cabbage, and a few other ones. The pigment in all belongs to one or more of the same family of red pigments, the anthocyanins. The betacyanins are another family of red pigments found mainly in members of the plants’ order known as Caryophyllates, including as the cacti. It is the yellow, orange to red colour we see in the ripe cactus fruit (the so named prickly pear). Betalain, which is a betacyanin, is the pigment responsible for the characteristic deep red to violet colour of the beetroots. Betacyanins are commonly used in food colouring. I tried hard but failed to identify a single naturally occurring pure blue edible fruit or vegetable. The ones I came across turned to be are artificially coloured for marketing purposes. Even if I proved to be wrong by someone naming the odd pure blue, my argument remains valid: Why naturally occurring edible blue food is so scarce? I was not surprised during my search to find out that others had struggled with same issue, well before I even realised it was an issue at all. What was pleasing though was the discovery that a famous intellectual comedian, whom I long admired as a social critic rather than a comedian, had his own humorous views regarding this matter. Below is an exact quotation of what George Carlin had said about the subject in the opening episode of “Saturday Night Live” in 1975: [Why is there no blue food? I cant find blue food — I cant find the flavor of blue! I mean, green is lime; yellow is lemon; orange is orange; red is cherry; whats blue? Theres no blue! Oh, they say, blueberries! Uh-uh; blue on the vine, purple on the plate. Theres no blue food! Where is the blue food? We want the blue food! Probably bestows immortality! Theyre keeping it from us!]
Posted on: Mon, 18 Aug 2014 09:47:17 +0000
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