Processed: Food Science and the Modern Meal

Heinz factory workers cleaning strawberries before canning, ca. 1904. To ensure the quality of its products, Heinz required workers to clean their nails weekly and shower regularly. (Thomas and Katherine Detre Library and Archives, Senator John Heinz History Center)

Heinz factory workers cleaning strawberries before canning, ca. 1904. To ensure the quality of its products, Heinz required workers to clean their nails weekly and shower regularly. (Thomas and Katherine Detre Library and Archives, Senator John Heinz History Center)

Some canning companies killed microbes with additives, such as sodium benzoate (which is still used today in canned food) and formaldehydes (now known to be carcinogenic), Levenstein says. According to Petrick, some of the larger canning companies, such as Heinz, Libby, and Campbell’s, installed expensive steam-retort technology developed in the 1870s. Steam retorts worked like steam engines, using pressure to raise canning temperatures high enough to kill pathogenic microbes. Smaller canning outfits relied on open kettles and had less consistent results. Yet some batches of cans, even when made with the era’s most advanced techniques, would explode after months on the shelf; the contents of other cans might mysteriously sour.

American canning companies eventually banded together to discover the scientific underpinnings of what was still mostly a craft, Petrick says. In 1913 they launched an industry-wide research agency, the Research Laboratory of the National Canners Association, to study the elusive bacteriology responsible for all manner of spoiled canned food. The research done by the agency in the decades that followed helped resolve the problem of spoilage and led to improved flavor, color, nutritional value, and texture.

Before this time canners had discovered through trial and error that the best way to avoid bad cans was to cook food at high temperatures for long periods, an approach that sacrificed flavor. “Food safety and palatability were often at cross-purposes,” Petrick remarks. One technique employed was adding salt to the vegetables. For string beans long cooking times leach out the green color, creating an unappealing grayish-toned bean, says Roger Clemens, a nutrition and food-safety expert. “By adding [salt] during processing, we could reduce cooking time and maintain the color.” (Yet what was once a desirable additive has become a modern health culprit, guilty of contributing to the rise in hypertension, heart disease, and obesity seen in many Western societies.)

One of the major canning innovations of the 20th century was the development of aseptic processing, notes food scientist John Floros. This technique, which involves sterilizing the container separately from the food, was invented in Switzerland in the 1960s for processing milk but is now used widely for canned tomatoes and many juices.

Small volumes of food are heated to a precise temperature and for a precise time in order to avoid overcooking and loss of nutrients, explains food scientist Philip Nelson, who won the 2007 World Food Prize for his research on making aseptic processing workable on an industrial scale. “When you put something in a can, you have to heat to the center, so you end up overheating what’s on walls,” says Nelson. Aseptic processing helps avoid this problem. “Then by storing [the food] in an oxygen-free environment you prevent reactions that affect flavor, color, and nutrients.”

In more recent decades the food industry has looked into alternative methods of making their products safe, including gamma irradiation, which preserves well but creates what Nelson describes as “wet dog–like flavors.” More successful, Floros says, is the use of pressure to preserve food. Fresh guacamole sold in supermarkets is pressure-processed to keep it from turning brown. Prepackaged raw oysters are also preserved with pressure.

Despite all the 20th-century alternatives, Appert’s technology—the can—still reigns supreme for long-term storage.

Uncovering the Mysteries of the Maillard Reaction

In 1997 construction workers digging a railroad tunnel in southwestern Sweden began to feel numb. Cows in the vicinity weren’t faring well either; some became paralyzed and eventually died. Fish in nearby waters floated to the surface.

Authorities discovered that acrylamide, a component in some of the sealant used in the tunnel and a potent carcinogen in rats, was to blame. Swedish toxicologist Margareta Törnqvis and her doctoral student Eden Tareke were called in to evaluate the exposure of tunnel workers to the dangerous substance. Their research unexpectedly led them to the kitchen and to the discovery that a cherished chemical reaction in food science, the Maillard reaction, also puts acrylamide in our dinner. The publication of these results in 2002 launched a decade-long transformation of the food industry as researchers tried to figure out how to avoid producing the poison.