Mary Engle Pennington

At the Food-for-Thought Café we serve fresh eggs and seafood in our California Salad. We tip our chef's hat to Mary Engle Pennington, a bacteriological chemist who used her scientific skills to improve the handling, packaging, and preservation of foods. She designed refrigerators for the home and refrigerated cars for railroads. Pennington created scientific standards for food transportation, allowing us to bring fresh, safe-to-eat ingredients to our tables from far away.

Courtesy the Collections of the University of Pennsylvania.

About Her Life

When people called Mary Engle Pennington (1872–1952) "The Ice Lady" it was because of her work, not her personality. She spent her career studying how best to use refrigeration to keep foods fresh and safe to eat.

Pennington was born in Nashville, Tennessee. Her mother was a Quaker from Philadelphia, and when Mary was a child the family moved to Philadelphia to be closer to her mother's family. At 12 years old, she discovered a book about medical chemistry at a local library. She was fascinated by the idea of atoms and molecules, that things she couldn't see were very real and had such a big impact on the world around her. It dawned on her that if all the invisible and unnoticed oxygen on Earth suddenly disappeared, all living things would die. "Like a flash in a dark place, I got the idea of the realness of the invisible world," she once recalled. Pondering things like this, she was instantly hooked on chemistry.

When Pennington was 18, she enrolled at the University of Pennsylvania, which was just a few blocks from her home. After studying science for four years she was awarded a "certificate of proficiency"—she had completed all the work for a bachelor of science degree, but the university didn't grant bachelor's degrees to women at that time.

Thankfully, Pennington's teachers felt differently about women's education, and they encouraged her to stay at Penn, where she eventually earned her Ph.D. She continued at Penn, carrying out postdoctoral research in chemical botany, then went to Yale University, where she did postdoctoral research in physiological chemistry. After that, she came home to Philadelphia and spent a few years working in medical labs.

In 1904 Pennington took a job with the City of Philadelphia, where she was in charge of ensuring the safety of milk and dairy products sold in the city. Her work was now more bacteriology than chemistry, and this would be true for most of her career. Contaminated food was a big problem in those days, largely due to unsanitary handling. Dairy farms weren't always sanitary, nor were the markets where people bought food. Ice cream sold by street vendors was especially unsafe. Pennington knew what needed to be done and that legal regulations were necessary, but she also knew she'd meet resistance if she tried to force the issue. Instead, she met with farmers and vendors to first explain the problem. She actually showed ice cream vendors slides of the bacteria that were found growing in their ice cream buckets. She convinced farmers of the need to inspect their milk before shipping it; and vendors, of the need to boil their buckets. When she finally pushed for laws requiring such practices, she met little opposition. The Ice Lady would become famous for this warm and personal approach.

Pennington soon caught the eye of the public health crusader Harvey Wiley, who recruited her to come work for him at the U.S. Department of Agriculture (USDA). Wiley had lobbied for the 1906 Pure Food and Drug Act, which created the Food and Drug Administration (FDA) to oversee the safety of food and medicines sold in the United States. Pennington became heavily involved in the activities of the FDA and was often called in as an expert witness in court cases involving accusations of food-safety violation.

At the USDA, Pennington did pioneering research on refrigeration and how it could be used to keep food safe from bacteria, which can spoil food. Bacteria grow faster in warmer temperatures, so naturally chilling food prevents bacteria from growing. Pennington researched the ideal temperatures for storing different kinds of food to prevent bacterial growth. She paid particular attention to eggs. (She even invented the modern egg carton to keep eggs from breaking during shipping.) Shipping food was a special problem because of the time it took to ship food from one end of the United States to the other, and food often went bad in transit. Pennington designed refrigerated railroad boxcars that were well insulated so that food stayed cold throughout its trip.

In 1919 Pennington left the USDA to work for a company that made refrigerator insulation, and in 1922 she started her own consulting business in New York City. She lived there until her death in 1952 at the age of 80.

For Further Reading on the Web

Mary Engle Pennington — a biographical snapshot from Journal of Chemical Education (JCE) Online, published by the Division of Chemical Education of the American Chemical Society.