Does the public furore aroused by Heinz and Twinings mean brands will always generate bad PR when they reformulate, asks Vince Bamford

There are some things it's best not to mess with: drunken squaddies, your best mate's sister and - as Heinz discovered this week - the taste of a well-loved brand.

When the company reduced the salt content of its HP Sauce it sparked fury among sauce fans who said it had lost the classic taste and caught the attention of the national press. Celebs have also piled into the fray, with Marco Pierre White regaling the Daily Mail with tales of how he was brought up on HP Sauce and how dodgy the new version is. It's a similar ­situation to the one tea producer Twinings found itself in a few weeks ago after The Grocer revealed that more than a hundred complaints had been registered on the company's website since it changed the flavour of its Earl Grey.

No brand wants this kind of trouble so is there a right way and a wrong way of reformulating?

Very much so, say industry observers, who cite many examples of reformulations that have worked including Walkers' switch to Sunseed oil and McVitie's fat reduction of its biscuits. And, with suppliers and retailers announcing last week that they will reformulate products to show the government they are serious about tackling the obesity crisis (The Grocer, 10 September, p4), many more businesses will need to make sure they adopt the right strategy.

The golden rule to any reformulation is to avoid changing either functionality, quality (including taste and texture) or price, says Richard Buchanan of branding agency The Clearing. "If you reformulate this sort of product and people notice then you haven't done your job," he adds. "When a product is as iconic and as close to the British as HP Sauce, you can't sneak a change under the radar."

While Heinz could be accused of trying to sneak the change past consumers, few (if any) reports have mentioned that the recipe was changed last November and that it has taken the best part of a year for people to complain. Perhaps Heinz would have got away with it if it hadn't been for those meddling hacks, but if the company had been up front about the change it might have avoided the uproar altogether, suggests Claire Nuttall of agency 1HQ.

"Brands need to tread carefully and take consumers with them," she says. "Education before and after the event is always helpful so consumers are being prepared and feel the brand cares what they think." Walkers, for example, took out ads in national papers when it switched to Sunseed oil in 2006.

Heinz was in a particularly difficult position with HP Sauce as despite having a few variants (including a reduced salt and sugar version) it is essentially a one-product brand. This factor, however, can work in favour of such a brand post-reformulation, adds Nuttall, as it is hard for consumers to find an alternative. "This may limit brand rejection, despite the current criticism," she says.

Meanwhile, Heinz says the cut in salt from 2.1g per 100g to 1.3g has not reduced the quality. "We are confident, as are the consumers who helped us with taste testing, that this has not affected the taste," a spokesman says.

Some consumers obviously disagree and with any reformulation suppliers must weigh the potential gains against the losses. Twinings revamped its Earl Grey following research that suggested consumers wanted a more citrus taste. "If Twinings had proof that this tweak would help it appeal to a wider audience then this would be a good commercial call, if seemingly tricky in the short term," says Nuttall.

With things looking a little tricky for Heinz right now, what should its next move be? Wait it out, suggests Nuttall. "Often these issues rage at the outset but seem to ­settle down quite quickly."

Not so, says Buchanan, who reckons Heinz should pay the price for breaking one of the golden rules. "They should apologise and change HP Sauce back," he says. "Then get to work on producing a version where consumers can't tell the difference."