A scientific research published in France has revealed that Coca-Cola and Pepsi contain traces of alcohol.
The revelation will cause concern among those who chose the carbonated soft drink for religious, health or safety reasons.
According to tests carried out by the Paris-based National Institute of Consumption (INC) more than half of leading colas contain the traces of alcohol.
These include the brand leaders Coca-Cola and Pepsi Cola, while it is mainly only cheap supermarket versions of the drink which are alcohol-free.
French magazine 60 Million Consumers publishes the results of the tests in its latest issue.
They suggest that the alcohol levels are as low as 10 mg in every litre, and this works out at around 0.001% alcohol.
But the figures will still be enough to upset the thousands of Muslims who regularly drink Cola because their religion forbids them from drinking alcohol.
Those who are teetotal and drink Coke regularly will also be worried, as will those who choose it as an alternative to alcohol when they are driving.
Of 19 colas tested, the nine which did not contain alcohol were made by brands including Auchan, Cora, Casino, Leader Price and Man U-Cola.
Ten which had traces of alcohol in them included Coca-Cola, Pepsi Cola, Coca-Cola Classic Light and Coke Zero.
Michel Pepin, scientific director for Coca-Cola France, said: “It is possible that traces of alcohol come from the process of making Coca Cola according to its secret recipe.”
He insisted, however, that Coca-Cola drinks were provably “soft” and recognized as such “by the government authorities in which they are sold”.
Michel Pepin added: “Furthermore, the Paris Mosque has provided us with a certificate stating that our products can be consumed by the Muslim community in line with the religious opinions of the Committee of the Mosque of Paris.”
A spokesman for Pepsi acknowledged that “some soft drinks can contain minute traces of alcohol because of the ingredients used”, although “the Pepsi Cola recipe does not contain alcohol”.
Both companies suggested that natural fruit can ferment and produce minute traces of alcohol.
Coca-Cola was invented in 1886 by the American John Pemberton and was originally patented as a medicine which could cure everything from headache to impotence.
It went on to dominate the international soft drinks market and is now a US icon sold in more than 200 countries.
However, caffeine is widely considered to be the main stimulant contained in the drink, along with vast amounts of sugar which have come to associate it with a range of health problems including obesity.
Every can of Coke contains approximately 10 teaspoons of sugar.