The ad shows a potato in a fries box and explains that it only uses the Russet Burbank, Shepody and Pentland Dell potatoes because they are particularly good for frying.
Under the headline: "The story of our fries. (End of story)", the copy in the ad reads: "We peel them, slice them, fry them and that's it".
The ad was challenged by a number of consumers who believed that the fries went through a number of extra processes before they reached customers.
One claimed that the product was flash fried in beef tallow, frozen while partially cooked before being flown to different parts of the world where they are re-fried; a second complainant believed that a significant amount of salt was added to the fries before they were served and questioned the health implications; and a third said a sugar solution containing dextrose was added at certain times of the year. The fourth complainant believed that the fries could contain glucose from other products, which were cooked in the same oil.
McDonald's, which faces constant challenges from pressure groups about everything from food preparation to its part in the growing problem of obesity among children, explained that it had not used beef tallow since 1993 and only cooked its fries in rape seed oil.
However, it did admit to the use of partial flash frying, which it said was common practice in the food industry and while admitting to adding salt at the last minute before serving, said fries could be customised for individual customer's requirements.
The company said that a certain amount of dextrose was present in potatoes anyway, but that when these levels were were low in a potato, fries turned an unappealing white colour. In this intance a low-concentrate solution was added to help maintain the golden colour of the fries all year round.
It also said that as far as cross-frying was concerned and whether this stopped its fries being gluten-free, only hash browns were fried in the same oil, which, like fries, are gluten-free.
The advertising watchdog accepted the advertiser's assertion that it does not use beef tallow and that its fries are gluten free, but ruled that the ad is misleading because wording such as "End of story" and "…and that's it", would lead consumers to think that the description on the ad was the complete process.
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