The humble pickled onion, long associated with classic pub culture, the ploughman’s lunch and cold festive buffets, is enjoying a revival as Britain’s appetite for pickles grows.

About 8.5m UK households bought pickled onions over the past year, according to the consumer data firm Worldpanel by Numerator, with particularly strong momentum in recent months.

In the 12 weeks to early August, the value of pickled onion sales rose 12% year on year, compared with 4% growth across total grocery. While higher prices have contributed to the increase, demand is strengthening, with about 300,000 more households buying them and more than 550,000 additional shopping trips made to buy them.

Pickles are more broadly moving beyond their traditional role as a side or accompaniment to become a flavour and ingredient in their own right.

Michelin-star chefs are even using them in their dishes, and this weekend marks the launch of London’s first major festival dedicated to pickling and fermentation: the Big Brine.

James Goodyear, the head chef at the Michelin-starred restaurant Gordon Ramsay High, said: “There’s a resurgence happening around pickling and preserving right now. Palates have evolved, so diners are naturally craving that sharp, mouthwatering punch of acidity and crunch to cut through richer dishes. Between social media demystifying the craft and a growing curiosity around gut health and natural fermentation, people are far more eager to explore beyond the basic supermarket jar.”

He said guests cared about “sustainability”, and having “jars quietly working away on the shelves” was a “smarter way of running a restaurant”. He added: “It lets us celebrate every single part of an ingredient and completely rethink surplus.”

Molly Scanlan, 39, from London is attending the Big Brine this weekend with her son and has noticed newer pickle brands in the supermarket. She “even noticed in a meal deal” recently the option of a “plastic sachet of snacking cornichons”.

Ocado data shows the pickles, gherkins and olives category is up 30% year on year, while fresh pickled and fermented products have grown 16%. Some individual products have had even more dramatic increases, including raw organic fresh ginger and lemon sauerkraut, up 393%, Opies cocktail gherkins, up 305%, Baxters sliced beetroot, up 246%, and Epicure spicy crinkle-cut pickles, up 242%.

Scanlan has been a fan of pickled foods from a young age. She says her son loves pickles, too, and he also likes kimchi.

Gherkins are Scanlan’s longstanding favourite, but she says there is a growing interest in a much wider range of fermented foods, with products such as kimchi and sauerkraut becoming more widely available. Part of the appeal, she says, is that “you can pickle anything”.

Matt Harris, the founder of Pickle Project, a London-based food brand that makes small-batch, handcrafted pickles using an ultrasonic brining process, said the brand had been created to bring “energy and fun” to what he described as an old-fashioned category. “Despite pickles having ‘a moment’, what’s available on supermarket shelves is very traditional,” he said.

Harris has introduced flavours such as deli dill pickle chips, while also experimenting with ultrasound technology to extract flavours from herbs and spices during the brining process. The brand has launched with Ocado and Whole Foods Market, and Harris said it had experienced “huge growth” over the past nine months.

Kat Goldin, a co-founder of the pickle brand Goat Rodeo Goods, said: “Over the last year, we’ve seen around 11-times growth in sales, which has been massive for us.” She added: “That also fits into this wider ‘lipstick effect’ culture we’re seeing. People might be cutting back on their grocery spending, but they still want to add a little bit of luxury or something special to everyday meals. A nice condiment or pickle can make a simple sandwich or salad feel more exciting without being a huge purchase.”

The pickle boom is also spawning entirely new formats, such as the UK’s first pickle sparkling water. Within its first week at Planet Organic, Yew sparkling water became the retailer’s bestselling soft drink, outselling even bottled water, while the brand says retailers have reported customers specifically asking for the pickle flavour.