Mary Engle Pennington, the Ice Woman
The term "ice woman" often conjures up an image of a heartless female, but in the case of Mary Engle Pennington, nothing could be further from that. Born into a Quaker family on October 8, 1872, she grew up in Philadelphia, Pennsylvania. At 12, she became fascinated in medicinal chemistry from a library book, whereupon she asked local university professors to explain it to her. Despite being told to come back when she was older, she enrolled after high school in 1890 to the Towne Scientific School (formerly Department of Science) at the University of Pennsylvania to study biology, chemistry, and hygiene. The university did not grant bachelor's degrees to women, so she had to be satisfied with earning a certificate of proficiency instead.
Wanting to go further, she learned of an old college statute which gave the faculty power to grant certain degrees like a doctorate without the approval of the board of trustees (who had denied her bachelor's degree), and that's what she achieved in 1895. She studied under Edgar Fahs Smith, department chair who considered himself more of a historical chemist than a practical one. Smith had just completed advising Fanny R.M. Hitchcock, the first woman to get a doctorate in chemistry at that university (1894) and the first director of the women's graduate department in 1897. So, Mary's environment was now quite conducive to her later success. She probably gained more than chemistry training from Smith, since he was known to emphasize the humanistic side of science not a commercial approach to learning chemistry. This included moral aspects of their work, instead of just studying to be skilled technicians.
She stayed on for two more years as a doctoral fellow, then spent a year at Yale University working with Lafayette Mendel and Russell Henry Chittenden, the two founding fathers of the science of nutrition.
Following that, she founded the Philadelphia Clinical Laboratory (1898-1906). She doubled as a bacteriologist with the Philadelphia Bureau of Health beginning in 1904, where she studied dairy samples for contamination. Pennington chose to teach farmers and ice cream salesmen about hygiene standards rather than just report the data. Basically, she just showed them what numbers of bacteria were in their samples under the microscope, and they immediately began boiling pots and ladles! Her standards for dairy quality became accepted nationwide.
In 1905, she added to her workload by accepting a position in the Department of Chemistry with the U.S. Department of Agriculture (USDA). One of her first projects was to investigate a claim that resturants had been served turkey meat that had been frozen for 10 years, but no customers had gotten sick. She showed that poultry could be kept frozen at -18ºC (0ºF) in good condition for one year.
Her director Harvey Wiley (the "father of the FDA") there was so impressed with her work that he wanted her to lead the new division which became responsible for the 1906 Pure Food and Drug Act. To do so, she had to pass a Civil Service exam, not often given to women. She signed her application as "M.E. Pennington" to hide her gender and got the highest score on the test. When the Civil Service authorities told her director there was no precedent for hiring a woman, he countered by saying there wasn't a precendent against it, and she was hired.
Two projects that she served on had immense importance to human health and earned her reputation as the "ice woman". First, she developed standards for the safe processing of chickens for human consumption. A simple but important finding was to keep fresh foods cold at a constant temperature. The 1906 Act didn't even refer to bacteria like Pasteur had shown half a century earlier in France. It just described avoiding "filthy, putrid,or decomposed" foods. Mary determined safe storage temperatures for many perishable food products like milk, eggs, and cheese. She also developed safer practices for handling raw poultry from slaughterhouse to market (Encyclopedia.com), as well as a new type of egg carton that reduced breakage during train shipping.
One example of her creativity is a patent she co-wrote in 1913 for a cooling rack for chickens and other meats. The rack could hold 180 chickens, ducks, or rabbits, 48-60 turkeys, or 72 geese in a design that maximized cooler space. Grading of the meat quality was easier and more accurate, too.
Pennington's second achievement in refrigeration with the USDA concerned railroad refrigeration cars. Experimentation in shipping meats cross-country began in 1842. Just after the Civil War, cattle were shipped from Texas to processing centers around the country, but the animals lost weight or died in the transport. Railroad companies initially did not like the new cars for refrigeration because they were one third more expensive and might be used only on one-way trips. Some were filled at the ends with ice blocks, and the floors were insulated with flax or cattle hair. Allowing meat to directly make contact against ice resulted in discoloration and affected the taste. So, ventilation schemes ranged from simply opening the doors to open rooftop hatches to fans driven by the car’s axles.
But the refrigerator was not a home appliance; people stocked cabinets called iceboxes with blocks of ice made artificially or harvested from frozen rivers and lakes. The first refrigerator was installed at a brewery in Brooklyn, New York, in 1870. The meatpacking industry followed with the first refrigerator introduced in Chicago in 1900, and it wasn't until 1913 that homes got their smaller models. Until such time as mechanical refrigerators were invented, ice sales were prominent.
Detroit, Michigan fish market owner William Davis devised a boxcar in 1868 with metal racks to hang the meat over a mixture of ice and salt. But the meat swayed and shifted the boxcar balance, sometimes causing derailments. Chicago meatpacking magnate Gustavus Swift then hired engineer Andrew Chase to make design improvements, and by 1881 he was sending 3,000 beef carcasses a week to Boston with almost 200 cars. Meats weren't the only food products shipped, and by the late 1890s, refrigerated shipping of all kinds of perishable foods including fruits and vegetables was done.
On October 3, 1908, Mary Pennington spoke to a Warehouseman’s Association in Washington, D. C. and explained the importance of cooling fruits immediately after being picked and not freezing them. She showed that freezing food products caused chemical changes that significantly changed the composition of the product. Not only did she also show off a railroad refrigeration car there and explain its usefulness (something rather novel at the time), but she road with it to California where it was tested for use in hauling fruits from the orange and lemon groves and then shipped them to Florida. Mary would travel with the car, check sensors, and carry out experiments along the way to improve their efficiency in transporting perishable foods. For example, she noted warm spots in the box cars and set standards for their construction to avoid such problems. Also, she found that the boxcar’s insulation was too thin and cracks could form in the exterior wall, exposing the scant insulation to the outside environment. She also discovered that meat should not touch and that boxes should have ventilation space between them.
By 1930, her experiments revealed not only flaws in boxcar construction, but she also developed solutions to them.
- Boxcar walls should be made with several thicknesses of material
- Between each one should be insulating material of recognized efficiency.
- It should completely surround the boxcar, and especially protect joints, seams and corners.
- Wood or metal could be used for the outside of the box, but it should be attractive and easily cleaned.
- The inside must be a material which moisture can't penetrate and which survives constant cleaning.
- The inner wall should not have a finish to absorb odors or hold moisture, because it would permit mold growth.
- Her examination found that only 3,000 out of 40,000 boxcars were certifiable.
Six months after World War I started, Dr. Pennington attended the National Poultry, Butter and Egg Association conference in Chicago in 1917, where she spoke to encourage farmers to increase delivery of poultry, eggs, and fish. As you can see below, her words reflected not only the scientific statements of a scientists but also her compassion as a Quaker.
“A hungry man may rise to a moment of valor, but when a whole people are hungry, they become moral and physical weaklings.”
“The supply of beef is not enough to go around and the deficit must be made up with other food.”
“We must feed our men in the trenches and the men of our allies. We must also feed the civilians of our own country and those of our allies.”
(Quotes from Wild Women of the West: Dr. Mary Pennington)
In 1919, Pennington resigned from the USDA and took a job director of American Balsa, which manufactured insulation used in refrigeration units. There, she created groundbreaking insulation techniques used on domestic refrigeration. A few years later, she started her own consulting company. The newly formed National Association of Ice Industries (NAII) contracted with her to be the head of their new Household Refrigeration Bureau. The NAII sought ways to increase ice sales in order to stock home iceboxes, but Pennington had other ideas to capitalize on her scientific credentials.
Her Bureau created pamphlets focused on the scientific basis of refrigerating foods and did not include any advertising of local ice dealers. This is important because the NAII had been formed in 1917 from 60 Chicago manufacturers and the publisher of the journal Ice and Refrigeration. She mailed from her New York City office only on request after home economics teachers, nutritionists, social workers, and other service professionals had seen them in circulars she sent out. Two notable titles were The Care of the Child's Food in the Home, Cold is the Absence of Heat, Journeys with Refrigerated Foods, and The Romance of Ice.
Pennington also contributed many articles to Ice and Refrigeration, such as the following:
- Standard Refrigerator Car Development (1919)
- Low Temperature in Transit (1924)
- The Construction of Household Refrigerators (1928)
- Fifty Years of Refrigeration In the Egg and Poultry Industry (1941)
- Refrigerated Warehousing of Tomorrow (1944)
She herself gave talks and a week-long Household Refrigeration School to teach ice company home service workers, mostly women, about the science behind spoiling of food. In 1927, she announced a "creed" for the Massachusetts Ice Dealers' Association; her Quaker roots caused her to write as one ideal of the creed: "There must be service, service, service, unselfish." Throughout the 1920s, she pushed ice manufacturers of the NAII to advertise for this service as a means to educate people (and as a side effect, it would help them to sell more ice). But by then, commercial refrigerators were on the market and had more advertising money to spend. When the stock market crashed in 1929, it was all over for the ice market, and Pennington stepped away from the Home Refrigeration Bureau.
She maintained her consulting business until she died in 1952. By then, she had earned 5 patents and received the Notable Service Medal from President Herbert Hoover, as well as the Francis P. Garvan–John M. Olin Medal, which recognizes women chemists. Wikipedia sums up more accolades as follows: She was the first woman elected to the Poultry Historical Society Hall of Fame in 1959. She was inducted into the National Women's Hall of Fame in 2002, the American Society of Heating, Refrigerating and Air-Conditioning Engineers Hall of Fame in 2007, and the National Inventors Hall of Fame in 2018.
Dr. Mary Engle Pennington died on December 27, 1952, at the age of 80.
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