When shoppers shop for dairy products, more often than not they check the expiration date. What does it mean and why is it there?

In most cases, the expiration date is a date set by a dairy bottler based on the number of days the product will retain its flavor following processing, which typically includes pasteurization, based on standard refrigeration practices.

Milk, for example, might be labeled by a certain dairy, for its freshness to expire 15 days after pasteurization. Some think of it as a "sell by" date, others consider it a "use by" date. If the milk has been properly refrigerated, it is typically safe for at least a week after the "sell by" date.

Recently, in New York City, the only city currently in the U.S. with its own expiration date requirements, the regulations have loosened from four days to nine days, and they have been debating eliminating the city ordinance altogether. Currently, NYC milk cartons have two dates – one of 15 days established by the industry, and a second one of nine days set by the NYC Board of Health.

Some think that is confusing, and unnecessary.

Why is milk dated? An unlikely answer to that can be found in, of all places, Alcatraz Island. During a tour of the former federal prison, a U.S. National Park ranger noted that Al Capone "lobbied for milk bottle dating to ensure the safety of the city's children."

Capone was a Chicago businessman who made a fortune in alcohol distribution during the brief period of Prohibition from 1920 to 1933. During this period, the demand for alcohol actually increased, with taverns being replaced with speakeasies, and the purveyors of "booze" labeled gangsters and racketeers.

Although Capone was sent to Alcatraz, it was for the white collar crime of evading taxes on the money he earned distributing alcohol, not for the numerous violent crimes attributed to him, such as the St. Valentine's Day Massacre.

Although the Federal government viewed Capone as a gangster, to many people in his adopted city of Chicago, he was a modern-day Robin Hood.

Capone was the first person to open a soup kitchen to feed the poor during the Depression. At a time of 25 percent unemployment, Capone's kitchens served three meals a day to ensure that everyone who had lost a job could get a meal. Soon, every city and town had a soup kitchen.

Capone did not only open them, but he would go to the soup kitchens and help serve the meals. These soup kitchens cost Capone thousands of dollars every day to keep running. It is said that Capone had a soft spot for people who were struggling.

It was reported that one of Capone's family members in Chicago became ill from drinking expired milk. At that time, there were no controls on milk production, neither expiration dates nor controls on adulteration, dilution or skimming of the cream.

This drew Capone's interest to the milk business, and he saw several things: the milk distribution business had a shady character – and Capone was comfortable with shady businesses; he didn't like to see people, especially children sickened by adulterated milk; he saw a potentially high profit in milk distribution; and with Prohibition soon to end, he had a fleet of trucks that could easily be used to transport milk.

Capone took two steps to move into the milk business. One was to acquire a milk processor, Meadowmoor Dairies. The other was to have the Chicago City Council pass a law requiring a visible date stamped on milk containers.

On the second item, it was likely that Capone had already cornered the market on equipment to stamp expiration dates on bottles, and the passage of the legislation would help him take over the Chicago milk market.

In 1930s Chicago, before refrigeration and supermarkets, milk was delivered by the milkman, a teamster's union member. The union controlled the distribution of milk, whose freshness depended on how long the milk sat around until the driver delivered it.

The unions would only deliver local milk. Meadowmoor Dairies wanted to import cheeper milk from Wisconsin, and wanted it delivered by their own nonunion truckers.

With the negotiations at a standstill, Capone's people reportedly kidnapped the union president and used the $50,000 ransom to purchase the dairy. The dairy was given as a present to Capone's attorney, William Parrillo. Meadowmoor Dairies opened three months before Capone went to prison.