Before running the Peanut Corporation of America, he along with his father and two brothers, ran a struggling $50,000 a year peanut operation in 1977 and transformed it into a $30,000,000 business and eventually sold it. Parnell bought another plant in 2001 and eventually started the Peanut Corporation of America when he bought an operation in Blakely and made it triple its revenue and turn a profit in 2004, the first profit it made in 15 years.
In 2009, Stewart Parnell shipped out tainted peanuts to various places across the United States, causing around 714 people to get sick from salmonella poisoning. At least nine people died from it and half of the people that got sick were children.
During the investigations, it was shown that several facilities had many health violations such as leaky ceilings, cockroaches, and rodents. Even worse, E-Mails were discovered that shown that Stewart knew about the tainted peanuts and didn't care and even faked lab tests to ship the peanuts out faster.
This lead to the largest recall of a food product ever recorded in American history and even thousands of pounds of food for food banks had to be discarded. The United States government then banned the Peanut Corporation of America from all government contracts for one year. The recall scared so many people they even refused to buy major brand peanut butters, despite the fact that the Peanut Corporation of America had nothing to do with them.
Less than 24 hours after the recall, Parnell filed for Chapter 11 bankruptcy.
Stewart, along with his brother, Michael Parnell, and Mary Wilkerson, the plant's quality control manager, were convicted guilty on September 19, 2014. The two brothers were estimated to 30 years of prison while Wilkerson was estimated for 20 years.