Q: Why does fresh orange juice taste so awful after you have just brushed your teeth? (continued)
A: Your correspondent (4 February 1995) has the wrong end of the stick as far as the explanation of the effect of toothpaste on the flavour of orange juice is concerned. This 鈥渙range juice effect鈥� has been well known for many years and has been the subject of much research and of several patents.
The obnoxious taste of the juice after brushing teeth has nothing to do with the alkaline ingredients of the toothpaste. Many toothpastes do not contain alkaline ingredients and the pH value of most, except those brands which have calcium carbonate as an abrasive, is almost neutral. Calcium carbonate, of course, results in a certain alkalinity, but this is not the cause of the strange flavour effect.
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Furthermore, the fluoride-containing components are not designed to 鈥渘eutralise the acids produced by bacteria鈥� but to strengthen tooth enamel to attack by these acids. Therefore it is not important for these components to be alkaline.
The nasty flavour is caused quite simply by the detergent used in the toothpaste 鈥� generally sodium laurylsulphate 鈥� to produce the foam that we are used to when brushing our teeth. This foaming serves no useful function except to provide the user with a visual signal that the toothpaste is doing a good cleaning job. If one could persuade the user to do without a foam and so omit the detergent, the orange juice effect would disappear. This negative effect on flavour is not limited to orange juice. Almost everything tastes different after brushing teeth 鈥� sometimes for anything up to two hours.