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 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 to improve its core menu items.

Last week, McDonald’s said sales rose 5.4 percent at established U.S. locations during the first three months of the year. But the company did not say how much of that came from an uptick in customer visits, versus higher prices.