NEW YORK (AP) — McDonald's is testing Chicken McNuggets with no artificial preservatives as it works to revive its U.S. business.

The world's biggest hamburger chain says it began testing the new recipe in about 140 stores in Oregon and Washington in March.

It's the latest move by McDonald's to step up the quality of its food as it works to stage a turnaround of its business, which has lost customers in recent years. The company has conceded that it failed to keep up with changing tastes and that it is looking at improving core menu items. Last week, it also said it is testing a version of its Big Mac that comes with bigger patties.

McDonald's did not provide details on what exactly is different about the new McNugget recipe, but said it is "simpler" and "parents can feel good" about it. As people have paid closer attention to food labels, companies across the food and beverage industry have tweaked recipes to remove ingredients that may be unfamiliar and unappetizing.

Last year, for instance, McDonald's tweaked its grilled chicken recipe to remove ingredients people might not recognize. That change removed sodium phosphates, which McDonald's said was to keep chicken moist, in favor of vegetable starch. Maltodextrin, which it said was used to increase browning, was also removed.

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Chicken McNuggets currently contain a long list of ingredients, according to the McDonald's website, including sodium phosphates. McNuggets are delivered to stores frozen.

McDonald's said was getting feedback from customers with the McNugget test, and did not say when it planned to launch the new recipe nationally. The McNugget test was first reported by Crain's.

Last week, McDonald's said sales rose 5.4 percent at established U.S. locations during the first three months of the year. The company did not say how much of that came from an uptick in customer visits. The results were boosted at least in part by higher pricing and the shuttering of underperforming stores.

McDonald's Corp., based in Oak Brook, Illinois, has more than 14,000 locations in the U.S.

McDonald's shares edged up 55 cents to $128.26 in morning trading Wednesday.