The return of the series uncovering secrets behind mass-produced food. Matt Tebbutt finds out why the shelf life for a vegetable stir-fry mix is so short, Jimmy Doherty uncovers the sweet secret of how ice lolly makers get such perfect layers in a rocket lolly and Kate Quilton travels to Portugal to discover just what piri-piri is.

Why does dropped toast always land the wrong side down? The truth about hard-to-peel oranges. And how come some love coriander and others think it tastes of soap?