As fast-food giants like McDonald's and Burger King embrace menu items made with plant-based meat alternatives, Chipotle CEO Brian Niccol remains skeptical.

In a new interview with Barron's, Niccol said he sees the plant-based foods movement as a "real trend," but questions whether certain products have staying power.

"I'm not sure plant-based foods that look and taste like meat are a long-term trend," Niccol told Barron's. He thinks consumers will shift to more plant alternatives in their diets, but that they won't necessarily be 100% committed to to vegetarianism or veganism.

"That's still a small group that are 100% vegan, [or] 100% vegetarian," he told Barron's. "It's definitely front and center. But right now, the way [plant-based meat alternatives are] processed, it just wouldn't match our brand purpose."

Previously, Niccol has criticized Beyond Meat, a meat alternative derived from pea protein and intended to taste and feel like meat, saying that the product is too processed to fit with Chipotle's ethos. Chipotle has always prioritized serving "real food made with real ingredients," according to the company's website.

(In response to Niccol's comments, Beyond Meat CEO Ethan Brown invited him to see their facility for a tour. "We believe our process is very clean," Brown told CNBC's The Exchange earlier this year in July.)

Still, Chipotle has found ways to serve customers who are looking for plant-based alternative protein sources. The chain currently offers "sofritas," a meat alternative made from organic tofu.

Unlike other plant-based options that are manufactured to mimic the flavors and mouthfeel of real meat, sofritas is just tofu and vegetables, such as peppers and tomatoes.

Taco Bell, on the other hand, revamped its vegetarian menu in early September to highlight bean-based menu items, rather than meat alternatives. Liz Matthews, Taco Bell's global chief food innovation officer said in a press release that the brand plans to explore the growing plant-based space.

Despite these mixed feelings, plant-based foods are on the rise. According to data from the Plant Based Foods Association, sales of plant-based meat alternatives in the U.S. grew 10% in the past year.

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