May 1, 2014 — -- Taco Bell has received a lot of attention for a reader-friendly ingredient explainer on its website.
It turns out many of the ingredients used in Taco Bell's beef are also used in other fast food chains' chicken nuggets for similar purposes, according to Derek Lowe, a blogger and chemist with a Ph.D. from Duke University.
Related: Taco Bell Explains Its Mystery Beef Ingredients
He said compounds found in a piece of fruit "may sound like a witch's brew of toxic sludge -- that is, if you don't know anything about chemistry or biology," he wrote in a blog post after the issue of Taco Bell's beef ingredient list got some major attention.
Bananas, for example, smell the way that they do largely because of isoamyl acetate, Lowe said.
Read More: Yum Brands Names Taco Bell Head as Next CEO
Here are some of the ingredients for chicken nuggets or tenders from four fast food chains.
McDonald's 4-Piece Chicken McNuggets:
McDonald's says its seasoning contains autolyzed yeast extract.
Lowe told ABC News that yeast extracts are "sheer umami," or a savory flavor, and not harmful.
"It's a way of adding MSG and getting the same savory flavor boost without adding MSG per se, in the same way that the 'all-natural no nitrite added' bacon that you see in stores always has celery powder or juice added to it. Celery is full of nitrite, plenty enough to cure meat, but when you do it that way you don't have to say that you added nitrite. Just celery juice," Lowe said.
2. Sodium phosphates
Sodium phosphate and similar ingredients treat meat during processing, Lowe said.
"Raw protein foods like meat and fish treated with phosphate hold water better as they cook, which means that there's less shrinkage, the end-product has more juice and has less chance of being tough," Lowe said.
3. Batter and breading
McDonald's says its leavening agent contains sodium acid pyrophosphate, an edible phosphoric salt that is leavening used for baking, such as baking powder.
4. "Prepared in vegetable oil"
McDonald's vegetable oil includes hydrogenated soybean oil with TBHQ, or tertiary butylhydroquinone, a preservative. It also contains citric acid, which is "added to preserve freshness," the company states on its website. It's used in candy and other foods for flavor. Taco Bell says it uses a "small percentage" in its beef recipe to "add brighter flavor."
McDonald's did not respond to a request for comment.
Wendy's Crispy Chicken Nuggets:
1. Sodium phosphates
"Grocery-store scallops are almost always phosphate-treated," Lowe explained, "which is why some cookbooks tell you to look for untreated ones if you're going to sauté or sear them," adding "the treated ones are just too moist to perform well."
2. Battered and breaded with...
Xanthan gum, which is an emulsifier or thickening additive to some foods.
3. Vegetable oil
Wendy's vegetable oil includes citric acid (called a preservative on Wendy's site) and dimethylpolysiloxane (described by Wendy's as an anti-foaming agent).
Wendy's spokesman Bob Bertini said, "We are proud of the quality food we serve, and provide complete ingredient and nutrition information for all of our menu items on our website. We do this so that consumers can make informed decisions regarding their personal dietary needs."
KFC's Extra Crispy Tenders:
1. SeasoningKFC says its "chicken flavor" includes maltodextrin, which is sometimes a sweetener.
2. Sodium Phosphate
3. Breaded With...
Monosodium glutamate (or MSG), maltodextrin, with no more than 2 percent calcium silicate added as an anti-caking agent, KFC says.
KFC spokesman Rick Maynard told ABCNews.com, “We buy our quality chicken from trusted companies and our restaurants receive fresh poultry deliveries throughout the week, where it is prepared by certified cooks. To ensure our customers have all the information they need, we provide complete nutrition and ingredient information on KFC.com.”
Burger King Chicken Nuggets (fried):
Includes maltodextrin (also used in Taco Bell beef as a sweetener), yeast extract, propylene glycol, which the CDC says is sometimes used as a solvent for food colors and flavors.
2. Sodium phosphates
A sweetener that is found in sometimes found in packaged desserts.
In response to a request for comment, a Burger King spokesperson said the chain's ingredients are safe and referred ABC News to the ingredients list on its website.