(CNN) Stewart Parnell once boasted processing the "finest" peanut products, but on Monday, the former company executive was effectively sentenced to life behind bars for knowingly shipping out deadly food.

A federal judge handed Parnell a 28-year prison sentence, the toughest penalty ever for a corporate executive in a food poisoning outbreak. Parnell is 61 and unless he wins an appeal, he will have to serve out most of his term.

His brother and food broker Michael Parnell received a 20-year sentence, and the plant's quality assurance manager, Mary Wilkerson, was given five years.

Parnell's trial was groundbreaking: Never before had a corporate executive been convicted of federal felony charges related to food poisoning. Parnell was facing up to 803 years in prison , and even though his sentence fell far short of the maximum, food safety advocates hailed it as a big step forward.

"Honestly, I think the fact that he was prosecuted at all is a victory for consumers," said Bill Marler, a food safety lawyer who represented several of the victims in the PCA outbreak.

Photos: Peanut butter trial Photos: Peanut butter trial When food kills – Jeff Almer breaks down after testifying before Congress about his mother Shirley, who died in late 2008 after eating salmonella-laced peanut butter with her toast. Almer became an advocate for stronger food safety regulations. Hide Caption 1 of 5 Photos: Peanut butter trial When food kills – U.S. Rep. Greg Walden, R-Oregon, holds up a jar of peanut products while questioning Stewart Parnell, owner and president of the Peanut Corp. of America, at a salmonella hearing in 2009. Parnell stands accused of deliberately shipping tainted food from his plant in Georgia. Hide Caption 2 of 5 Photos: Peanut butter trial When food kills – Lab tests found salmonella in a 5-pound container of King Nut peanut butter at a Minnesota nursing home. It was manufactured at Peanut Corp. of America. Hide Caption 3 of 5 Photos: Peanut butter trial When food kills – Peanut Corp. of America owner Stewart Parnell, right, and former plant manager Samuel Lightsey testify before Congress about the 2008-2009 salmonella outbreak linked to their company. They were both indicted later on criminal charges that resulted in a groundbreaking trial. Hide Caption 4 of 5 Photos: Peanut butter trial When food kills – Stewart Parnell exercised his Fifth Amendment rights and refused to answer lawmakers' questions about Peanut Corp. More than five years later, he is on trial with his brother and a former employee. Hide Caption 5 of 5

"Although his sentence is less than the maximum, it is the longest sentence ever in a food poisoning case," Marler said. "This sentence is going to send a stiff, cold wind through board rooms across the U.S."

For Jeff Almer, Parnell's sentencing brought relief. He had been seeking justice for his mother, Shirley Mae Almer, who died in late 2008 after eating salmonella-tainted peanut butter. Still, the day was filled with mixed emotions.

"I am satisfied there were convictions and now jail terms," he said. "But less so in that all this could have been avoided."

A deadly outbreak in 2008

The 2008 salmonella outbreak traced back to peanut butter paste manufactured by PCA killed nine people and sickened 714 others, some critically, across 46 states. It was the deadliest salmonella outbreak in recent years and resulted in one of the largest food recalls in American history -- from Keebler crackers to Famous Amos cookies to the snack packets handed out on airlines.

Suddenly, one of America's favorite foods had turned into a killer.

Parnell invoked the Fifth Amendment when called to testify before Congress and had never publicly spoken about the tragedy until Monday, when he expressed remorse in the courtroom. His family members also testified Monday on behalf of his character and asked for mercy.

His lawyer, Scott Austin, said Parnell was devastated by the 28-year sentence. Parnell has maintained all along that his company engaged in commercial fraud but that he was not aware of it.

But the loved ones of those who died asked that Parnell pay for his deeds.

Almer, who traveled with his sister from Minnesota to make his statement in court, blames Parnell for his mother's death and had been waiting for this day in court. He said he has grown weary from constant talk of his mother's death for almost seven years.

His grief and his anger toward PCA turned him into a food safety activist. Before Parnell's sentencing, Almer and other family members of victims sent U.S. District Court Judge W. Louis Sands a letter asking for $500,000 in restitution that would go to food safety groups.

"We have lost our loved ones and have worked hard to help to prevent this from happening to others," said the letter, which Almer shared with CNN. "Our request is not a selfish request; we only ask that you assign any monies to aid families who have suffered or are suffering from food borne illnesses."

Carl Tobias, a University of Richmond law professor, said Parnell's sentence will make corporate executives think twice before engaging in wrongful activities.

"I don't have the impression that Parnell set out to kill people," Tobias said. "He just ran his business in a way that caused a lot of injury and some deaths. The sentence was appropriate and maybe it should have been stiffer."

Kevin Pollack, whose company Stericycle ExpertSOLUTIONS helps handle brand recalls, said various foods are recalled every year because of bacterial contaminations, which can lead to illness. The PCA case, he said, is historic in that a corporate executive was held accountable with a prison term for knowingly distributing tainted food.

"Manufacturers already pay attention, but they will take note that if they were to fail, there can be serious ramifications," Pollack said.

Activists have been working for years to get tough with enacting and enforcing food safety laws.

The Food and Drug Administration estimates that every year, 48 million people -- one out of six -- suffer from food-borne illnesses. More than 100,000 people are hospitalized and about 3,000 die from infections the federal government says are largely preventable.

In early 2011, as a result of the campaign launched in the aftermath of the PCA outbreak, President Barack Obama signed the Food Safety Modernization Act, which the FDA called the most sweeping reform in food safety laws in 70 years.

For the first time, the law took aim at preventing food-borne illnesses rather than just responding to contamination that had already occurred. The new law gave the FDA the power to suspend a facility's ability to sell food in American markets and detain food that may be contaminated.

Advocates: Stronger law, weak funding

The problem, say food safety advocates, is there is not yet adequate funding for the FDA to fully enforce the law.

Marler, the lawyer who has represented victims of all sorts of food-borne outbreaks, said he was relieved that his clients in the PCA case are seeing justice. But he said more needs to be done on the front end -- before tragedy strikes.

"I'd rather Stewart Parnell never go to jail, [and] that the outbreak had never happened."

At trial last year, prosecutors called 45 witnesses and presented more than 1,000 documents including months of emails, lab results and financial records to make their case that Parnell knew about the contamination, covered it up and ordered PCA to continue shipments of salmonella-tainted peanut paste used to manufacture a variety of products.

The prosecution's blistering opening statement contained three now-infamous words Parnell wrote in a March 2007 email to a plant manager about contaminated products: "Just ship it."

Stewart Parnell invoked the Fifth Amendment at a congressional hearing.

Defense statements and witnesses, which took all of 104 minutes, portrayed Parnell as a small-business owner who was scapegoated by the government. Defense attorneys argued that Parnell did not know about mismanagement at the plant and that he was the fall guy for other employees' wrongdoing.

The prosecution was a rarity, Marler said, because the Department of Justice charged the Parnell brothers with felonies. Prior cases involved misdemeanors.

"Prosecutors took a risk and fortunately, the jury believed them," Marler said. "The jury saw this for what it was. The emails and documents told a story of a company that was more interested in shipping out products than products that were safe."

Most common food-borne illness

Salmonella is America's most common cause of food-borne illness and sickens up to 1.4 million people every year.

A current outbreak of salmonella from cucumbers has infected 418 people in 31 states, according to the Centers for Disease Control and Prevention. The Arizona Daily Star reported the death of a woman after eating a tainted cucumber.

In the PCA outbreak, former company employees described filthy conditions at the plant in southwest Georgia. Federal inspectors found roaches, rats, mold, dirt, accumulated grease and bird droppings during their raid. They also found a leaky roof.

Salmonella is often associated with meat, poultry, eggs and raw milk -- products from animals that are carriers of the bacteria. It also thrives in the intestines of birds and can be found in fruits and vegetables and in ingredients made from them.

The presence of water in what is supposed to be a dry processing facility for peanuts is like adding gasoline to fire for salmonella, food safety experts say.

Health officials discovered similar poor conditions at PCA's other processing plant in Plainview, Texas. The company filed for Chapter 7 bankruptcy protection shortly after it was shut down.

Two former plant managers worked out deals with the government in exchange for their testimony.

"The sentence that was handed down today means that executives will no longer be able to hide behind the corporate veil," said U.S. Attorney Michael J. Moore of the Middle District of Georgia.

"The tragedy of this case is that at a peanut processing plant in Middle Georgia, protecting the public lost out to increasing of profits. This case was never just about shipping tainted peanut product; it was about making sure individual wrong doers were held accountable and the losses suffered by the victims and their families are never forgotten."