The team find out what makes food fit for a celebration. Helen Lawal finds out how tall a celebration cake can go. Jimmy Doherty unravels the secrets of a classic party food, the samosa; and investigates why there's so much air in a bag of crisps. Kate Quilton discovers how the shape of celebratory chocolates can change how they taste; gets her hands dirty helping a world champion create a sugarwork showpiece; and finds out what separates cordial from squash. Briony May Williams learns all about bags of ice, and how to really mix a martini and Matt Tebbutt dons a lab coat to explore the science of party food.

Kate Quilton and John Whaite go on an incredible journey to unearth the origins of the K-foods that have exploded in popularity in recent years. Starting in Seoul, they uncover the crispy secrets of Korean Fried Chicken and reveal the key ingredient in Gochujang sauce. Continuing south to Icheon, they investigate a rice-based alcoholic spirit that outsells all others in Korea. In Cheonan they discover the reason for the massive popularity of pork luncheon meat - aka spam - and find out how it's made. A short detour to the beach at Dacheon leads to a surprising and unforgettable seafood with a nickname fit for the playground. Finally, in Gwangju, they enter a world of kimchi, and learn the key to its global expansion.

Jimmy Doherty and Matt Tebbutt embark on an extraordinary road trip through America's Deep South. Starting on the Gulf Coast, in New Orleans, they discover how the shells from the huge number of oysters consumed locally could protect the coastline. Heading through Mississippi, Jimmy and Matt find out what makes southern sweet tea different from a British cuppa. In Alabama, Matt wants to know why they fry green tomatoes, and Jimmy uncovers exactly what grits are. Then it's off to Tennessee to visit the Jack Daniels distillery and discover the secrets of sour mash. In Louisville, where the South meets the North, Jimmy and Matt learn about fast-food consistency at Kentucky Fried Chicken HQ.

Andi Oliver and Matt Tebbutt journey through the islands of Barbados, Saint Lucia and Dominica to unearth the secrets of Caribbean food. In Barbados, they learn about rum production at Mount Gay, before finding out why hunting and eating lionfish could be good for the local ecosystem. In Saint Lucia the pair discover red bananas at a local market and head to Hotel Chocolat's Rabot Estate to find out why chocolate's flavour depends on where it is grown. They take a ferry to Dominica and discover a bread made by the Kalinago people with only the cassava root. Then, the duo meet a passion fruit farmer and discover why the fruit has such an evocative name.

Kate Quilton finds out if there is any difference between soft and crusty bread rolls, and Andi Oliver reveals why chocolate chips don't melt when baked in cookies. Andi also asks why pre-made sandwiches always seem to have mayonnaise in them, Matt Tebbutt uncovers some of the secrets of ready meals and Briony May Williams discovers the surprising science of how canned food can last so long.

The team delve into some fruity favourites. Jimmy goes to India to investigate pomegranate health claims while Kate finds out why cucumbers are wrapped in so much plastic. Briony finds out how many apples go into one can of cider and why strawberry juice is so elusive in supermarkets. Matt finds out why some fruits are hairy and travels to Spain to discover why some oranges are harder to peel than others.

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

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?

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.

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.