It was Mr. Rahal who made the contacts with the four buyers who took bribes. He was caught on a wiretap in April 2008, promising to help Mr. Watson with his tax payment, according to court papers. In another conversation, reported by a witness, Mr. Rahal explained the art of ascertaining whether a person would be susceptible to bribery.

Image Credit... Illustration by The New York Times

According to court papers, Mr. Rahal recounted how he would drop a $100 bill on the floor, then bend to pick it up, saying: “You must have dropped this. Is it yours?” If the person said yes, Mr. Rahal considered him receptive. Mr. Rahal pleaded guilty to racketeering, price fixing and money laundering charges in December 2008 and has been cooperating with investigators. His lawyer, Christopher D. Adams of New Jersey, did not respond to requests for comment.

Mr. Rahal is accused of bribing ingredient buyers as early as 1998. One of those he is said to have drawn in was a New Jersey buyer named Robert C. Turner Jr., who began taking bribes while working as a purchasing manager at Nabisco. In 2004 he went to work for B&G Foods, the maker of Ortega Mexican foods and other products, in Parsippany, N.J. Mr. Turner continued to take bribes as he rose to become B&G’s director of purchasing.

Mr. Turner, an Eagle Scout, confessed to taking more than $65,000 in bribes in all. He pleaded guilty last May to mail fraud charges related to bribe checks he received in the mail. Mr. Turner’s lawyer, John A. Azzarello of New Jersey, said Mr. Turner was not aware that SK Foods was shipping tomatoes with high mold counts and other defects.

In one case in 2007, Mr. Turner raised the price B&G paid on a contract to finance his own kickback. In that deal, B&G agreed to buy 13 million pounds of peppers from SK Foods at 22 cents a pound. But at Mr. Rahal’s urging, Mr. Turner added an extra penny a pound. The pair agreed to “split the penny,” meaning that each of them would pocket half a cent a pound, for a total of $65,000 apiece.

Kraft, the nation’s largest food manufacturer, appears to have been among the biggest companies skimmed by the bribes. Court papers say that Kraft bought about 230 million pounds of processed tomatoes from SK Foods from 2004 to 2008, as Mr. Watson took $158,000 in bribes.

Mr. Watson did not cooperate with investigators and is so far the only person sentenced in the case. He is serving a 27-month prison term and has been ordered to make $1.8 million in restitution to Kraft. A request to meet with Mr. Watson in prison was submitted to his lawyer, Thomas J. Organ of Illinois, who did not respond to follow-up calls.