Burger King is testing its meatless “Impossible Whopper,” and if all goes well, it could roll out the vegetarian, environmental patties at its 7,200 locations nationwide. Meanwhile, McDonald’s is working to rid its global beef supply of antibiotics.

These giants of fast food are responding to the changing concerns and palates of the consumer—particularly the millennial consumer—which aren’t simple modifications to make, said Suresh Acharya, a professor of the practice in the Robert H. Smith School of Business.

“From a consumer perspective, there’s a whole area that is starting to really get attention, called the ‘ethical supply chain,’” he said in an interview with Spend Matters. “And it has a fairly broad umbrella around anything that is environmental or sustainability-related.”

Acharya, who specializes in statistical optimization solutions for supply chain management problems, said there’s more focus now on how animals and humans are treated throughout the supply chain. For example, consumers say they are 60% more likely to eat at restaurants or are willing to pay more if they know that antibiotics are not used in those products.

In 2017, McDonald’s, which doesn’t raise its own animals, updated its Global Vision for Antibiotic Stewardship in Food Animals, promising to “preserve antibiotic effectiveness in the future through ethical practices today.” A year later, it pulled antibiotic-fed chicken from its menu.

Now, its focus is beef, which could prove more complicated because—compared to the poultry industry with its relatively few large suppliers—the beef industry is fragmented. Technologies such as blockchain—a method of distributed, secure digital information storage—may be able to help both audit as well as to track violators, Acharya said.

“The biggest challenge is to ensure that all of the beef suppliers actually comply with the new policy,” Acharya said. “It is one thing to have them pledge and say that they will comply, but that results in the question of whether there will be an audit process and what kind of mechanisms are in place to ensure that the suppliers are living by their words.”

Burger King’s addition of the Impossible brand’s increasingly popular fake meat—which is moist and “bleeds” like real meat—also takes aim at the problems of antibiotic resistance. And it could fight global warming by reducing the number of methane-producing cattle that are bred for carnivores.

The move is likely to spark a trend that will spread widely across the quick-serve and fast-food industries, Acharya said.

“When you look at some of the surveys, it’s really the millennials who are willing to pay extra and buy things that they perceive as being healthier, more environmentally friendly, more humane, all of that,” he said. “I think everyone would essentially have to follow.”