When she was a little girl in Essex in the 50s, Linda Miller would go over to her neighbour Barbara’s house every Friday night and together they would sit on the front step eating crisps. There was only one flavour widely available back then – Smith’s plain potato crisps, which came with a small blue sachet of salt that could be sprinkled over them. One Friday night, the two friends struck upon an idea. “We thought we’d invented a new crisp,” says 68-year-old Miller. Inspired by their weekly fish and chip takeaway, the pair “saturated” their plain crisps with a bottle of vinegar. “It was lovely, lovely – very tasty,” Miller says. “When salt and vinegar crisps came out, I remember thinking: ‘They’re not as good as what we do.’”

Crisps were first mass-produced in the early 20th century, but the first flavoured crisp was released only in the late 50s, after Joe “Spud” Murphy, the owner of the Irish company Tayto, developed a technique to add cheese and onion seasoning during production. Salt and vinegar crisps were launched throughout the UK a decade later, in 1967, when Miller was 16.

In her lifetime, a transformation has taken place on supermarket shelves. Should you want to, you can now buy not only bacon, chicken, chilli and pickled onion crisps, but truffle, pink peppercorn gin, baked camembert, masala chicken, brie, Aberdeen Angus beef, salted caramel, katsu curry and sriracha. (To this day, Miller prefers to vinegar her own crisps.)

Because the UK is so multicultural ... it gives us more leeway to use more unusual or interesting flavours Tassy Goodall

How is it possible that, in 60 years, British shops have gone from selling one crisp flavour to selling hundreds – and why are seasonings becoming more unusual? What led Kettle Chips to release a “truffled cheese and a splash of English sparkling wine” flavour in October? Was there a mad scientific breakthrough that caused Walkers to release bratwurst, paella, haggis and spaghetti bolognese crisps in 2010?

In the beginning, says the food historian Nadia Berenstein, industry experts thought of crisps as potatoes. What this means, she explains, is that early seasonings mimicked the flavours that would accompany traditional potato dishes – salt and vinegar, cheese and onion, and barbecue sauce in the US. Although synthetic chemical compounds for flavouring were developed in the middle of the 19th century, Berenstein says the industry exploded after the second world war with the invention of a device called the gas chromatograph, or GC.

“The GC was a really powerful tool for identifying the volatile compounds that are present in and contribute to flavours,” Berenstein says. “Just being able to figure out, isolate and identify these things prior to the GC took a long time. To study the flavour chemistry of apples, you’d have to start with a literal tonne of apples and then process those down to a concentrate of a couple of milligrams.” For the first time, gas chromatography allowed food scientists to quickly understand the chemical compounds behind complex flavours such as cheese.

In an October 1955 issue of a US industry magazine called Potato Chipper, “Bar-B-Q” flavouring was described as “the most sensational new development in the industry”. The excitement around the new possibilities was palpable. In a later issue, an X-ray nurse from Cincinnati was crowned “Miss Potato Chip of 1956” (“She is five feet eight inches, blonde, and weighs 125 pounds,” declared the magazine). Pete Cardy, a 63-year-old from Hertfordshire, recalls visiting the Ideal Home Exhibition at Olympia in London as a child in the 60s and seeing a vendor selling smoky bacon crisps. “It really blew my mind,” he says of sampling the snack. “It was: ‘Wow,’ it was just so exotic.”

Tayto’s Joe ‘Spud’ Murphy (second left) started the flavoured-crisp market in the late 50s. Right: boxes of Smith’s plain crisps, which came with a salt sachet, in 1975. Composite: Mr Tayto/Facebook; Mirrorpix via Getty Images

A warehouse worker at a Golden Wonder warehouse in 1970. Ready salted remains the UK’s favourite crisp flavour. Photograph: Mirrorpix/Getty Images

Crisp history is remarkably spotty: debate rages about which company invented which flavour. When I contact Walkers to ask for a rough timeline of when its flavours were released, I am sent a document with “????” written between the 70s and the 00s. Amateur archivists paint a fuller picture. Wayne Tomlinson, a 51-year-old from Doncaster who has collected more than 8,000 crisp packets since the 80s, stores them, neatly pressed, in cardboard boxes around his home. He also has four boxes of new, unopened flavours waiting to be tried. Over Christmas, he tasted and reviewed a new packet every day, including lobster cocktail, ham with spiced cola and even roast potato flavour.

“A big 80s flavour was spring onion,” says Tomlinson. “Now virtually no brands do it.” Tomlinson – who helps run the 972-follower Facebook page Crazy Bout Crisps and is on the Seabrook Crisps taste-test panel – says the 80s were “experimental”; he started collecting crisp packets after enjoying unusual limited-edition flavours such as Smith’s gammon and pineapple. He reminisces fondly about unusual early flavours such as Tudor’s limited-edition chocolate (he posted the flattened purple and brown foil packet to the Facebook page) and Smith’s novelty run of hedgehog flavour, although he shudders at the memory of Seabrook’s sweetcorn. As a teenager, he was allowed a packet of KP cheese and onion crisps for supper at exactly 8.30pm. “Every night, we would eagerly await it.”

Think about the complexity of flavour in individual ingredients. You can see just how complex our work can get Matt Cullingworth

Tomlinson points to the amalgamation of crisp companies as a reason for the decline in unusual flavours after the 80s (Smith’s, for example, was bought in the 90s by PepsiCo, which owns Walkers; its Bovril flavour didn’t make the cut). From there, crisp flavours became fairly standardised. Sarah Lawson, the marketing manager for the British brand Tyrrells, says 70% to 80% of its sales come from four flavours: lightly salted, salt and vinegar, cheddar and chive, and sweet chilli.

But the market changed again, Berenstein says, roughly a decade ago. “It’s not that there’s been any kind of technological breakthrough that has allowed for these things that were previously only dreamed of,” she says. “It’s a new understanding of consumer desires and a new pace of production. It’s a bloodbath out there in the supermarkets.” New, limited-edition and mystery flavours attempt to capture the market by “promising something new and different”, she says.

For Walkers, novelty arrived in 2009 in the form of its “Do us a flavour” competition, which asked the public to come up with seasoning ideas. The winners – among them chilli and chocolate, cajun squirrel and builder’s breakfast – led the way for the brand’s 2010 World Cup range, including yorkshire pudding, bratwurst, garlic bread, salsa, paella and haggis flavours.

Tassy Goodall, a chef who works with Sainsbury’s to develop its Taste the Difference crisps, says that the UK crisp market has been influenced by global food trends. “Because the UK is so multicultural and we’re quite well connected with different cultures through restaurants specialising in different cuisines like Middle Eastern food and regional Indian dishes, it gives us more leeway to use more unusual or interesting flavours.”

In the past few years, a number of studies have found that Britons and Americans are increasingly replacing their meals with snacks, with a 2018 survey by Listerine reporting that one-third of Britons eat only one meal a day. Matt Smith, the marketing director of the Northern Irish crisp-maker Tayto (a separate brand from the Irish firm of the same name), says earlier crisp flavours were inspired by things you could put in a sandwich (hence the launch of prawn cocktail flavour in the 70s), but because potatoes have a “clean flavour” they are the perfect vehicle for emerging food trends. Berenstein concurs: “In contrast, something like yoghurt or a beverage can be challenging to flavour because you have to design flavours that go along with the acid and the dairy.”

You could argue, then, that crisp flavours have gone from being inspired by lunch to being inspired by dinner, while at the same time our dinner options have expanded exponentially. “We know 36% of young people want to explore new flavours all or most of the time, and 51% of snackers are always on the lookout to try new snacks,” says Lexie Mackintosh, a Sainsbury’s product developer. “It’s that sort of customer insight that’s driving our push to develop new flavours.”

When it comes to creating those flavours, things get a little trickier. Matt Cullingworth, a research and development director at PepsiCo who runs sensory panels for brands such as Walkers, says Christmas pudding flavour was “exceptionally challenging” to make. “Think about how many ingredients there are in a dish – and the complexity of flavour in individual ingredients. You can see just how complex our work can get,” he says. Smith tests the flavours on members of the public selected for their tasting skills (before you apply, he warns that only 25% of us have sufficiently refined palates).

Mixing it up ... brands including Mackie’s and Tyrells have launched unusually flavoured crisps.

Original and best? Despite the plethora of choice, traditional flavours are still popular. Photograph: Les Gibbon/Alamy

Sweet flavours such as Christmas pudding started cropping up in 2016 (the Scottish brand Mackie’s launched strawberry, while Pringles released sugar cookie and pecan pie). This led the way for the launch of alcohol flavours. Phil Hovey, a developmental chef at Kettle Chips, created the brand’s truffled cheese and a splash of English sparkling wine flavour because it was looking for a little luxury. He explains how, when eating crisps, you may pick up some flavours first and then be hit with an aftertaste. Seasonings are made in everything from fine powders to large grains; “the larger pieces you taste later, the smaller pieces you taste earlier”.

Hovey works on roughly 12 new flavours at any one time, but he says only half of these see the light of day. “I spend a lot of time working in the future. It takes me eight months to make a seasoning, so I’m trying to make something that’s going to be bang on trend in eight months’ time.” Sometimes this means the chef misses the mark – his team have been known to cry: “What are you making?!” – while other flavours make it to taste-testing groups that ultimately disapprove.

Like Sainsbury’s developers, Hovey agrees the current snacking trend is all about “food adventure” – he travels around street markets, food fairs and festivals to get inspiration. Yet Lawson at Tyrrells says an appetite for luxury also drives trends, arguing that economically uncertain times means people treat themselves in smaller ways. “People tell us it’s a way of showing how much they care about their friends and families because they’ve given them something special they’ve gone out and found. So it’s quite an emotional thing – it’s not just: ‘Oh, I’m going to try these crazy crisps,’” she says. To tie in with the wedding of the Duke and Duchess of Sussex in 2018, the brand launched ginger-flavoured crisps that were dusted with edible glitter.

Yet Lawson says Tyrrells is moving away from anything “a bit wacky” to focus on firm British favourites. In 2018, the brand’s raspberry bellini flavour was a flop. “I think the flavour was probably a little too out there for some of our fans and we’ve learned from that,” Lawson says. “Sometimes when we launch something new, you get a bit of excitement, but it doesn’t actually perform that well.” The exception is the brand’s truffle flavour, which is now its fifth-most popular seller. Lawson puts this down to Tyrrells’ demographic – older shoppers with “foody interests” and “discerning palates”.

It seems that lessons have been learned from flavouring fads – many sweet flavours have disappeared. Indeed, there is still an overwhelming appetite for the staples. At Tayto, Smith says cheese and onion represents one-third of its sales, while ready salted remains the most popular on the market as a whole. “However many years on, they’re the ones we still all go back to,” he says.

So, what is next for crisps? Hovey believes the demand for “bolder and bigger” flavours isn’t going anywhere, while Berenstein says that nothing – not even a climate apocalypse – can break the seasoning spirit.

“Climate change is going to change agricultural production: people will eat less meat, there will be finite availability of certain kinds of produce, or at least a higher cost to pay,” she says. “But I think, because flavour is potent in very small quantities, it’s one of the things you’ll be able to expand.” As our food options shrink, Berenstein argues, artificial flavourings could become more prevalent as we look to mix up our limited diets.

“It’s easier for me to imagine a climate change dystopian grocery store that is full of potato chips perfectly enhanced with cricket protein, in every flavour imaginable, than it is for me to imagine a shrink in the number of flavour opportunities,” she says.

As for Tomlinson, he says he picks up two to three new flavours to try every week – and there is no sign of things slowing down. “Some days you can eat more than others,” he says. “I live on my own, so I can be quite non-standard with my meals … I try to eat at least one proper meal a day and, for the other meals, either in the middle of day or the evening, just have a couple of bags of crisps.”