Jimmy Doherty, Kate Quilton and Matt Tebbutt present some of their favourite investigations. In Israel, Kate unearths the mystery ingredient that makes icing sugar so light, fluffy and powdery. She takes a dip in the Dead Sea before all is revealed at an enormous phosphate mine in the desert. Skyr is a mysterious yoghurt-like product that claims to be entirely fat-free but is surprisingly creamy. So what exactly is it? In Iceland, Jimmy grapples with a team of wrestlers who say they swear by the stuff, before a trip to the factory reveals that it may not be a yoghurt at all. In Cornwall, Matt dives for the edible seaweed that has started cropping up on supermarket shelves. Can we eat any old seaweed? And how does seaweed spaghetti match up in a blind taste test against pasta? Kate also heads to Spain, in pursuit of the perfect tomato.