SINGAPORE - Indulging in after-works drink could soon become a less "sinful" activity.

Researchers from the National University of Singapore (NUS) have created a new sour beer which contains a probiotic strain that can neutralise toxins and viruses, as well as regulate the immune system.

It is the brainchild of Ms Alcine Chan, 22, a fourth-year student from the university's faculty of science.

She came up with the idea as she consumes probiotic drinks frequently, but noticed that most of them were dairy products, which people who are lactose intolerant or allergic to proteins may avoid.

"While good bacteria are often present in food that has been fermented, there are currently no beers in the market that contain probiotics," said Ms Chan.

"Developing sufficient counts of live probiotics in beer is a challenging feat as beers contain hop acids that prevent the growth and survival of probiotics."

Every 100ml of the beer contains one billion probiotics - the intake of probiotics per serving recommended by the International Scientific Association for Probiotics and Prebiotics. The final product has an alcohol content of about 3.5 per cent.

The beer, which Ms Chan took nine months to perfect, is her final-year project and was produced with the help of Associate Professor Liu Shao Quan from NUS' Food Science and Technology Programme.

Ms Chan had experimented with five other probiotic strains, and managed to succeed with the Lactobacillus paracasei strain after varying factors, such as temperature and the amount of ingredients, during the brewing process.

The beer takes about a month to brew, and Ms Chan and Prof Liu have filed a patent for it. Prof Liu said that a Japanese company has expressed interest.