Mary Engle Pennington: The “Cold Chain” of Food Safety
Pennington’s interest in science was apparent early when, at age 12, she became fascinated with a book on medical chemistry. She went to the University of Pennsylvania and demanded that a professor there explain to her what she had read. The professor suggested that she learn to read and spell the words and return when she was older, promising to help her when she did so.
She studied chemistry and biology at the Towne Scientific School at the University where she received a "certificate of proficiency" rather than a B.A. because degrees were not granted to women at the time. She went on, however to earn a Ph.D. in 1895 from the University of Pennsylvania, which had become one of the few universities in the country at that time to grant such degrees to women.
Unable to find a job following graduation, she formed her own Philadelphia Clinical Laboratory where she began conducting bacteriological analyses. Pennington began by working to clean up the ice cream supply peddled to school children by educating farmers in the handling of raw milk. In 1905, Harvey Wiley began to work with Pennington on cold storage problems.
After the 1906 statute was passed, Wiley ask Pennington to head the Bureau of Chemistry’s Food Research Lab. Pennington achieved the top score on the Civil Service exam to enter federal service, and her work was well known to him so Wiley disguised the fact that she was female by submitting his hiring request under the name of M.E. Pennington. When his ruse was discovered, he prevailed by arguing that the civil service law did not allow him to not hire her just because she was a woman.
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| Baltimore Inspector Earnshaw inspects a dirty egg packing facility circa 1912. |
Pennington’s job was to help implement the 1906 Act. Her laboratory conducted pioneering research leading to the recognition that fresh foods could keep much longer without spoiling when they were kept at a constant low temperature. By eliminating temperature fluctuations, bacterial counts remained low. This was important because the law itself never referred to the microbes of Pasteur but merely condemned food deemed "filthy, putrid,or decomposed."
Pennington’s worked helped establish that maintaining low bacterial counts in refrigerated foods such as eggs, milk, and cheese was critical to food safety and purity. Pennington steadfastly refused to appear in court hearings or allow her staff to do so, keeping her sole focus on research.
In 1919 she left civil service to continue her work on food preservation and then developed new interests in the safety of the new frozen foods that dominated the later years of her professional life.