Gregg Wallace is in Lowestoft, at an enormous factory where they produce 450 tonnes of frozen food each day. He follows the production of frozen potato waffles, from the arrival of 25 tonnes of potatoes right through to dispatch. Along the way he discovers how they make a monster amount of mash and marvels at the technology which stamps out a million identical waffles every 24 hours, each weighing 68 grams and exactly 15 mm thick.

Meanwhile Cherry Healey is learning about the differences between waxy and floury potatoes and finding out which spud you should use for which job. Small waxy potatoes are best in salads and boiled, while floury potatoes produce the best mash and roasties. She's also asking whether, in these carb-conscious days, we're unfairly demonising the potato. At King's College London she meets a dietician who runs tests which show that the potato, gram for gram, has more vitamin C than beetroot and carrot and more potassium than banana. Keeping hold of these nutrients isn't easy. But Cherry is delighted to discover that skin-on wedges, as long as you go easy on the oil, are a nutritional winner.

Historian Ruth Goodman is myth busting Walter Raleigh's connection to potatoes. She discovers that he couldn't have brought them back from North America, because there weren't potatoes there until 20 years after he died. Instead the credit must go to Spanish explorers and an enterprising French chemist called Parmentier, who popularised this exotic new vegetable. She also meets one of the inventors of the potato waffle, who shows her how Mr Whippy ice creams were the inspiration behind this teatime treat.

Gregg Wallace is in Burton upon Trent at Britain's biggest brewery, where they produce 3 million pints of beer a day. He follows the production of Britain's best-selling lager from raw barley to finished cans. Along the way he gets to grips with brewing terms like mash, wort, grist and coppers, and learns how 0.2 millilitres of yeast is enough to make 1.3 million pints alcoholic. In this high-volume factory he marvels at a machine that can fill 165 cans in just 5.5 seconds.

Meanwhile, Cherry Healey is learning how four basic ingredients – water, malted barley, hops and yeast – can be manipulated to make dark, heavy ales, light, fragrant lagers and everything in between. She is also uncovering the secrets of the perfect pint in a scientific study which shows that drinking beer from a curved glass makes it taste fruitier, while a frothy head and a higher temperature also improve flavour. Which is a win for the traditional British warm pint.

Historian Ruth Goodman is asking why Burton became the centre of brewing in Britain in the 19th century. The answer is that it is all in the water. The hard water there was perfect for brewing flavourful stouts and porters. While its position on the canal network made it ideally placed to transport finished beer round Britain and beyond. She is also finding out how beer got its stereotypically blokey reputation, despite the fact that brewing was traditionally a female profession. It is all down to the introduction of hops in the 15th century, which turned beer making from a cottage industry into an industrialised process.