Surprise rippled across America last month as a new wave of consumers discovered that hamburgers often contained ammonia-treated beef, or what critics dub "pink slime."
What they may not have known is that ammonia - often associated with cleaning products - was cleared by U.S. health officials nearly 40 years ago and is used in making many foods, including cheese. Related compounds have a role in baked goods and chocolate products.
Using small amounts of ammonia to make food is not unusual to those expert in high-tech food production. Now that little known world is coming under increasing pressure from concerned consumers who want to know more about what they are eating.
"I think we're seeing a sea change today in consumers' concerns about the presence of ingredients in foods, and this is just one example," said Michael Doyle, director of the University of Georgia's Center for Food Safety.
Ammonia, known for its noxious odor, became a hot topic last month with the uproar over what the meat industry calls "finely textured beef" and what a former U.S. government scientist first called "pink slime".