By Jeanne Yacoubou, MS

In March 2025, The VRG received an inquiry from a British documentary company asking if we knew of any products that currently use L-cysteine derived from animal sources.

As we have reported in past articles, L-cysteine was commonly used as a dough conditioner in a wide variety of foods especially bread products such as pizza dough and bagels. Its most common sources traditionally have been human hair or duck feathers.

For this update, we contacted several restaurant chains and food companies about their current use of L-cysteine.

McDonald’s

In 2010, we confirmed that McDonald’s pies contained L-cysteine derived “from an animal source.” We noticed on the ingredient statement for its apple pie in September 2025, that L-cysteine was still listed. We contacted McDonald’s USA through their website contact form to see if their L-cysteine was still derived from an animal source.

Their generic email reply did not mention L-cysteine nor did it lead to a website page with specific information about this ingredient. So, we called the customer service line. The customer service representative informed The VRG that the L-cysteine in their apple pie was derived from “hog hair, human hair, or poultry feathers.” She was unable to be more specific concerning the most likely source when we asked.

On the other hand, on the McDonald’s Great Britain website in 2025 we observed the statement (dated May 21, 2018): “We can confirm that if L-cysteine is used in any of our food it will not be derived from hair or animal origin.”

Pizza Hut

The apple pie at Pizza Hut does not contain L-cysteine and neither do their pizza doughs. The Thin ‘N Crispy dough at Pizza Hut is vegan. The other crust varieties contain a few questionable ingredients which we have asked about. When we hear back from Pizza Hut, you will find a report on our blog.

Domino’s Pizza

According to Sean Hislip, Director of Quality Assurance at Domino’s who relayed to us in October 2025: “I can confirm that our L-cysteine is still microbially-derived.” Readers may recall that in 2021, we reported that Domino’s had already been using microbially-derived L-cysteine for years.

Of the six crusts at Domino’s, only the thin crust is vegan, according to the complete ingredient statements on their website.

Papa John’s

Papa John’s lists their full ingredient statement on their website. None of their three pizza crust varieties contain L-cysteine. Vegans should note that their gluten-free crust contains egg whites and whey.

Little Caesars

Little Caesar’s also lists their full ingredient statement on their website. L-cysteine is not listed in any of their four types of crust. Their classic round crust is vegan. The VRG had questions about several microingredients in their other crusts and we’re awaiting responses to our questions. Any further information we receive will be posted on our blog.

Hunt Brothers Pizza

Hunt Brothers Pizza does not have an ingredient listing on their website. They called us back about L-cysteine in their pizza and stated “it is microbial; it is not derived from animals.”

Other Pizza Chains

For this article, The VRG also reached out to California Pizza Kitchen and Giordono’s, as well as Costco and Martin’s stores which distribute Giordono’s products. Giordono’s dough contains a “dough additive” for which we don’t know the source. When we had not received a response after two weeks from anyone, we inquired a second time by phone. If we should hear back, we’ll report their answers in our blog.

Dunkin’

As its lengthy and comprehensive ingredient lists reveal, Dunkin’ bagels do not contain L-cysteine. In fact, unlike many chain food stores and restaurants which refrain from using the term vegan even for demonstrably vegan foods, a Dunkin’ customer service rep called all its bagels (except the sour cream & onion variety) vegan. He also referred to their hash browns and English muffins as vegan.

Bruegger’s Bagels

A complete ingredient statement is posted on the Bruegger’s Bagels website. No L-cysteine is used. Most of the bagel varieties are based on the plain bagel which is vegan. A few of them contain sugar of an unspecified source. The two wheat bagels at this chain contain honey.

Other Bagel Chains

The VRG also reached out twice to Einstein’s Bagels and Bethesda Bagels. If we get a response, we will post it here.

Mellow Mushroom

In 2014, The VRG reported that the pita bread at Mellow Mushroom contained L-cysteine. When we checked back with them in 2025, we learned that they no longer have pita bread on their menu. Their pizza dough, pretzel bites, burger buns, and hoagie rolls are not made with L-cysteine. Currently, there is no vegan or vegetarian burger available at Mellow Mushroom. They offer tempeh and Follow-Your-Heart dairy-free cheese on their pizza.

Panera Bread

Offering a wide variety of bread products, Panera does not publish on their website a complete list of ingredients in a single document as many restaurant chains do. However, diners can access an ingredient statement on the page for each menu item with a couple extra clicks from their menu button then scrolling down to the button labeled “See all ingredients” to find it. To view their full 2021 menu in a single document, viewers may visit this third-party site.

Panera bagels do not contain L-cysteine. The ingredient statements list dough improver with a helpful parenthetical expression after it containing all components. All bagel varieties, including the plain bagel, contain sugar of an unknown source. Dairy may be in some types. The sprouted grain bagel contains honey.

None of the breads contain L-cysteine but a few contain dairy, honey, or sugar from an unknown source. The sourdough breads, artisan ciabatta, black pepper focaccia, and French baguette are vegan. Many of the breads and bagels contain sorbitan monostearate which could be derived from an animal source. We asked Panera about their source and were told by Nicole in Guest Care “our sorbitan monostearate…is vegetable-sourced.”

L-Cysteine in Food Products

The VRG scoured the internet to determine if L-cysteine is present in any food products today. We did not uncover many. Here are a few that may interest vegan bakers or bread lovers. Note that we asked several major bread brands but heard back from only one.

• Martha White Thin and Crispy Pizza Crust Mix is listed as containing the chemically similar cysteine hydrochloride as a dough conditioner. We asked the manufacturer for more information and learned that this compound is derived “from an animal source.” No further information is available.

• Fleischmann’s Pizza Crust Yeast contains L-cysteine. We spoke with a customer service representative in September 2025 who was not able to answer our question about this ingredient’s source. She escalated our question to Fleischmann’s nutrition team. A few days later we received this email response from Fleischmann’s customer support team: “The L-cysteine in the Fleischmann’s Pizza yeast is synthetic. The enzyme is not animal derived. Fleischmann’s Yeasts are vegetarian.”

Since this reply was confusing since (1) L-cysteine is an amino acid (not an enzyme); and (2) the term synthetic is vague, we asked for further clarification including whether their synthetic L-cysteine were microbially-derived. They replied a few days later with: “It is not microbially-derived; it is a synthetic ingredient (plant-derived). We are unable to provide further details as this information is proprietary.”

This response is also confusing in that it asserts a synthetic ingredient is plant-derived but not microbially-derived. Usually, synthetic means something is microbially-derived (i.e., synthesized by microbes via fermentation) or made from fossil fuel-derived substances (i.e., petrochemicals).

We suspect that Fleischmann’s is using Wacker’s “plant-based” L-cysteine which is produced from a fermentation process using bacteria. If so, it would be correct to call their process microbial as well.

• Sara Lee breads also contain L-cysteine. We asked their customer relations department about its source and were informed by email: “The L-cysteine that we use is extracted from duck feathers.”

Microbial L-Cysteine and Alternatives

Microbially-derived L-cysteine manufactured for commercial uses in the food industry has been available for decades but is still cost-prohibitive for most food companies. Wacker-Chemie, a German company, developed the fermentation technology for making L-cysteine using bacteria. Wacker partnered with Kyowa Hakko USA to make this ingredient available in the United States. Wacker markets their L-cysteine as “plant-based” referring to the carbohydrate medium (e.g., corn) fermented by microbes.

There is some research into creating L-cysteine from several enzymatic reactions using gene cloning in an in vitro pathway referred to as metabolic engineering, but no petrochemicals are directly involved. This method involves genes—likely of microbial origin—to yield L-cysteine, but not via traditional microbial fermentation.

The Lesaffre Corporation is another company that uses microbes to produce dough conditioners that function as L-cysteine substitutes. In this case, inactive yeast is used. Jim Gluhosky, the Senior Technical Services Manager at Lesaffre, wrote to us that they currently sell four different types of fungal L-cysteine substitutes, including one that is certified organic.

L-Cysteine Recommendation and Conclusions

As a general rule, we recommend that you contact a food company or restaurant chain about its source of L-cysteine when in doubt. Note that L-cysteine could be present in a packaged food but subsumed under general terms on ingredient labels such as dough conditioner or dough additive without being explicitly stated.

L-cysteine derived from human hair or poultry feathers is still used in foods today but not as commonly as it was decades ago. It is no longer the first-choice dough conditioner likely because of the ick factor. Unlike calf-derived rennet, which has been almost completely replaced by microbially-derived rennet (except in some specialty cheeses), the same cannot be said for L-cysteine in 2025 for economic reasons. Continued public pressure for “clean” food ingredients—especially non-animal sources—may lead to even more brands choosing microbially-derived L-cysteine or substituting plant-, microbial-, or mineral-based dough conditioners for L-cysteine.