It's been described as "the soya sauce of European cuisine": Verjuice--the unfermented juice of unripe fruit, often grapes. The Greeks used it, the Romans used it, the French, the Italians... And even we used it until the Industrial Revolution. Most farmhouses would have kept a barrel made from crab apples... Now Michelin chefs are queuing up to get hold of it again. But is it worth using in our own kitchens? Sheila Dillon visits food historian Ivan Day and hears from Verjuice 'crusader' Maggie Beer in her vineyard near Adelaide, South Australia. She tastes what is currently on the market and samples some historic verjuice-based dishes.