Ketchup is the smooth, glossy, bright-red tomato condiment that has become one of the most widely used sauces on earth — a thick purée of cooked tomatoes balanced by vinegar, sugar and a quiet background of spices. Its flavour is a tightly engineered four-way chord of sweet, sour, salty and savoury umami, designed to wake up fried, grilled and griddled foods. Despite its tomato identity today, the name and the idea descend from a family of dark, salty, fermented Asian sauces that contained no tomato at all.