Briony May Williams finds out why some radishes are hotter than others. Andi Oliver wonders why pre-made sandwiches seem to invariably have mayonnaise in them, while Kate Quilton heads north to the Scottish isles to discover how they are growing truffles.

More fun facts about our food. Why some fruits are hairier than others, the difference between single and double cream, and the science of canned food and why it keeps so long