Mary Engle Pennington

When you visit a supermarket with a refrigerated or frozen food section that is used to protect the safety of your food, you are seeing the direct result of the work of Dr. Mary Engle Pennington.

Completing all the requirements for a B.S. degree in chemistry, she was denied an actual degree because she was a woman and given a certificate of proficiency instead. Continuing her education, she completed a doctorate program at the University of Pennsylvania but was only allowed to earn an actual degree though a loophole that made exceptions for female students in “extraordinary circumstances.”

Working as a bacteriologist with the Philadelphia Bureau of Heath, Pennington was instrumental in improving sanitation standards for the handling of milk and milk products, including educating farmers on proper handling of raw milk that was used to create the ice cream sold to school children. Her work included a checklist of procedures for dairy herds that was adopted throughout the United States.

With her reputation in the field firmly established, she was hired by the U.S. Department of Agriculture as a bacteriological chemist to work on cold food storage problems. As more people in the United States moved to cities in the early 1900s, the shipping of food long distances became a concern and in 1906 the U.S. passed the Pure Food and Drug Act to secure the food supply.

The director at the Bureau of Chemistry encouraged Pennington to apply for a position as chief of the newly created Food Research Laboratory and she was appointed in 1907. This lab would conduct pioneering research that would lead to the understanding that fresh foods like eggs, milk, and cheese could keep longer without spoiling when they were kept at a constant low temperature, inhibiting the growth of bacteria.

Leaving the civil service in 1919, she was hired by a manufacturer of insulation for refrigeration units and in 1922 she started her own consulting business where she oversaw the design and construction of modern refrigerated warehouses, as well as commercial and home refrigerators.

Written by Angela Goad