Umami, or the mysterious fifth taste, went undiscovered for thousands of years. Its presence makes food taste savoury, not just as the absence of sweetness, but as a particular taste in itself. (Think asparagus, Parmesan or cured meat.) It is a sensation triggered by most of the dishes that we eat. It is something that most of us will taste a few times a day, every day of our lives. So we might expect to be a little more familiar with the idea of umami. And yet, after thousands of years of exposure, it was only just over a century ago that someone noticed it.