Source: http://theweek.com/article/index/253227/...

The technology behind the taste synthesizer isn't complicated. It works by reproducing four of the major taste components in varying degrees and ratios: Salty, sweet, sour, and bitter. (No umami, though. At least not yet.) Those tastes are tickled,according to New Scientist, by fooling the tongue's taste receptors with "a varying alternating current and slight changes in temperature controlled by semiconductor elements that heat and cool very rapidly."

If that doesn't sound very appetizing, that's because it isn't. The technology is still incredibly new, and you still have to stick out your tongue and let a clunky piece of metal zap it. At the moment, though, Ranasinghe and his team are working on compacting the technology down into a "digital lollipop" which will allow users to, say, taste test a box of expensive chocolates online before they hit the buy button.