Plot: Jimmy Doherty looks into skyr, a mysterious yoghurt-like product that claims to be entirely fat-free, but has a surprisingly creamy texture, while Kate Quilton heads to one of the busiest oyster hatcheries in France, where she witnesses the amazing science that goes into providing oysters year-round. Plus, Matt Tebbutt wants to know if the dried strawberries in his cereal are real or just a clever imitation