NEW YORK — McDonald’s wants to explain why its burgers may not rot and that there are no worms in its beef.

The world’s biggest hamburger chain is confronting unappetizing questions as part of a U.S. campaign to beat back perceptions that it serves Frankenfood. The company has run similar campaigns in Canada and Australia and said Monday it’s bringing the effort to its flagship market.

The push comes as McDonald’s fights to boost its performance in the U.S., where sales slid 1.5 percent at established locations in the most recent quarter, following a 0.2 percent dip for last year. In addition to increased competition, McDonald’s is trying to keep up with changing tastes, with places such as Chipotle marketing their food as more wholesome alternatives.

To improve the image of its food, McDonald’s recently rolled out chicken wraps with sliced cucumbers and the option to substitute egg whites in breakfast sandwiches. It also plans to eventually let people swap out the french fries in value meals with options like salad or vegetables.

For its latest campaign, among the first issues McDonald’s addresses are widely circulated online images and videos that show its burgers staying in tact after several weeks or even years. On its webpage, McDonald’s says that’s likely because the food has dehydrated, and that food needs moisture to form mold.

The company’s responses to other questions such as “Does McDonald’s beef contain worms?” are more direct: “No. Gross! End of story.”

A video posted on the company’s home page also showed Grant Imahara, a former host of the TV show “Mythbusters,” touring a Cargill beef plant where McDonald’s patties are made.