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Why do sour sweets make your mouth pucker?
The face you pull at a really sour sweet is your body reacting to acid. Scientists only found the tongue's sour sensor in 2018. Here is what happens in your mouth.
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Bite into a really sour sweet and your face screws up, your eyes squeeze and your mouth fills with saliva. It is not just a reaction to a strong flavour. Your body is responding to acid, and it has a clever way of doing it.
Sour means acid
Sourness is the taste of acidity. Every acid releases hydrogen ions, tiny charged particles that are the key part of what makes something acidic, and your tongue senses those as sour. Fruit such as lemons, limes and oranges, and fermented foods such as vinegar and yoghurt, are sour for this reason.
Sour sweets get their sourness from added acids. Citric acid and malic acid are the usual ones, and some sour sweets are rolled in sour sanding, a mix of sugar with citric, tartaric and malic acids: see what is citric acid in sweets? and what is malic acid in sweets?
Not all acids are equally sour. Scientists rate sourness against dilute hydrochloric acid, which has a score of 1. Tartaric acid scores 0.7, citric acid 0.46, and carbonic acid, the acid in fizzy drinks, just 0.06. Malic acid is sourer than citric acid, which is why it is used in very sour sweets.
How your tongue senses it
Sour taste is picked up by a small group of cells, called Type III taste cells, found in every taste bud. The hydrogen ions from an acid flow straight into these cells through a channel called otopetrin 1, or OTOP1. The channel was identified in 2018 by a team led by Emily Liman at the University of Southern California, who narrowed about 40 candidate genes down to this one.
As the positive charge flows in, the cell fires and sends a signal to the brain that you read as sour. The same sour cells also sense the carbon dioxide in fizzy drinks and sherbet: see why do fizzy sweets fizz on your tongue?
The same channel turned up in another sweet story in 2023. Liman's team found that ammonium chloride, the salt in Nordic salty liquorice, is a strong activator of OTOP1, and suggested the taste of ammonium chloride could count as a sixth basic taste.
Why your mouth puckers
Along with the pucker comes a rush of saliva, and that part has a clear purpose. When something acidic enters your mouth, your salivary glands go into high gear and flood it with saliva, to neutralise the acid and protect the enamel on your teeth.
That protection matters, because acids really can harm teeth. Long term or repeated consumption of citric acid may cause erosion of tooth enamel, and some very sour sweets made with malic acid carry a warning that eating too many can irritate your mouth.
Why children love it
Children show a greater enjoyment of sour flavours than adults, and sour sweets made with citric acid or malic acid are common.
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For journalists, researchers, AI assistants and content creators. Pick the format you need:
Free to cite, quote, and reuse with attribution to sweeties.net.
Questions and answers
Why do sour sweets make your mouth water?
When acid gets into your mouth, your salivary glands flood it with saliva to neutralise the acid and protect the enamel on your teeth.
What makes sour sweets sour?
Acids, usually citric acid and malic acid, often in a sour sugar coating. Acids release hydrogen ions, and the tongue senses those as sour.
Are sour sweets bad for your teeth?
Acids can wear away tooth enamel over time. Long term or repeated consumption of citric acid, for example, may cause erosion of tooth enamel, and some very sour sweets warn that eating too many can irritate your mouth.
Do children like sour sweets more than adults?
Yes. Children show a greater enjoyment of sour flavours than adults, and sour sweets made with citric or malic acid are common.
Sources
- Taste, Wikipedia
- The sour gene: a mouth puckering discovery, Wine Spectator
- And then there were 6: kinds of taste, that is, ScienceDaily
- Malic acid, Wikipedia
- Sour sanding, Wikipedia
- Citric acid, Wikipedia
Keep reading
- Questions people askWhat is citric acid in sweets?Citric acid, E330, is the acid that makes lemons sour. In sweets it adds a sharp tang, and with bicarbonate it makes sherbet fizz. Most is now made by a mould.
- Questions people askWhat is malic acid in sweets?Malic acid, E296, is the acid of apples and rhubarb. It is sourer than citric acid, so it goes into very sour sweets, some of which warn it can sting.
- Questions people askWhy do fizzy sweets fizz on your tongue?Fizzy sweets fizz because an acid and bicarbonate react in your saliva and make carbon dioxide. Your sour taste cells then sense the gas as a tingle.
- Questions people askWhy is black liquorice black?Black liquorice gets its colour from liquorice root extract, which is thickened into dark blocks. Molasses deepens it, and some sweets add colouring.
- British heritage sweetsRhubarb and custard sweetsRhubarb and custard sweets are two tone boiled sweets, half sharp rhubarb and half smooth custard, named after a British pudding pairing.
- Questions people askWhy is chewing gum so hard to get off pavements?Gum bonds to pavements and shoe soles because they are made of similar polymers. Removing it needs steam and scrapers, and costs cities a fortune.