If a biochemist can be spotted by its blue-stained fingers, the color blue might be often overlooked in the kitchen. For this first column, we will turn our attention to two blue ingredients in our kitchens: red wine and bananas.
Blue hides in red wine. Anthocyanins give its color to the royal drink:
those polyphenols gives in fact their colors to many flowers, fruits, berries and vegetables. Among which we can name pansies, eggplants, cherry, apples, raspberries, blueberries and grape. Acting as a natural sunscreen, anthocyanins protect the plants from the lights radiations that chlorophyll itself does not absorb or in other occurrences from other oxidative damage. Funny thing about them: their absorbance spectrum vary in a pH-dependant manner; red for acidic solutions, blue for alkaline and purple around neutral (anyone ever wondered where the Litmus test came from?).
Here is the funny hands-on part : to make some blue (and unpalatable) wine, just add some alkali to your red wine! 1M NaOH should do the trick (watch out : too much of it just gives a nasty brown). And duh… do I really need to tell you not to drink the wine afterward?
We have seen that red can be blue. Now, let’s see why, when bananas are involved, yellow also
can be blue… Yes, they are blue. No? You were not looking at them under the right light: try UV instead (have you never brought a banana in a bar?). Your banana will turn a bright, electric blue. During ripening, as chlorophyll is degraded, bananas lose their green color, with only some carotenoids left to give the usual yellow. Chlorophyll being a porphyrinoid, its breakdown products can present surprising light-absorption characteristics. It appears that the secret of that fluorescent surprise resides in one of those metabolites, only recently discovered and termed FCC-56 (Fluorescent Chlorophyll Catabolite). Now, biochemists just have to figure the exact role of those metabolites for the plant... Piece of cake
Blue hides in red wine. Anthocyanins give its color to the royal drink:
those polyphenols gives in fact their colors to many flowers, fruits, berries and vegetables. Among which we can name pansies, eggplants, cherry, apples, raspberries, blueberries and grape. Acting as a natural sunscreen, anthocyanins protect the plants from the lights radiations that chlorophyll itself does not absorb or in other occurrences from other oxidative damage. Funny thing about them: their absorbance spectrum vary in a pH-dependant manner; red for acidic solutions, blue for alkaline and purple around neutral (anyone ever wondered where the Litmus test came from?).Here is the funny hands-on part : to make some blue (and unpalatable) wine, just add some alkali to your red wine! 1M NaOH should do the trick (watch out : too much of it just gives a nasty brown). And duh… do I really need to tell you not to drink the wine afterward?
We have seen that red can be blue. Now, let’s see why, when bananas are involved, yellow also
can be blue… Yes, they are blue. No? You were not looking at them under the right light: try UV instead (have you never brought a banana in a bar?). Your banana will turn a bright, electric blue. During ripening, as chlorophyll is degraded, bananas lose their green color, with only some carotenoids left to give the usual yellow. Chlorophyll being a porphyrinoid, its breakdown products can present surprising light-absorption characteristics. It appears that the secret of that fluorescent surprise resides in one of those metabolites, only recently discovered and termed FCC-56 (Fluorescent Chlorophyll Catabolite). Now, biochemists just have to figure the exact role of those metabolites for the plant... Piece of cakeFor further reading about anthocyanins and wine color:
Jensen J. S. et al. 2008 Prediction of Wine Color Attributes from the Phenolic Profiles of Red Grapes (Vitis vinifera) J. Agric. Food Chem., 56 (3), 1105–15
The discovery of the fluorescence in bananas (how come no one saw that before?): Moser S. et al. 2008 Blue Luminescence of Ripening Bananas Angewandte Chemie. 47(46), 8954-7
The discovery of the fluorescence in bananas (how come no one saw that before?): Moser S. et al. 2008 Blue Luminescence of Ripening Bananas Angewandte Chemie. 47(46), 8954-7
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