Mary Engle Pennington: The Mother of Modern Food Preservation

Mary Engle Pennington: The Mother of Modern Food Preservation

Mary Engle Pennington. From the National Inventors Hall of Fame website.

The preservation of food and beverage products for safe consumption despite extended shelf lives at grocery stores is a major global industry. Both consumers and companies have soon to be Hall of Fame member Mary Engle Pennington to thank.

Research on the worldwide food preservation market released by Research and Markets in 2016 predicted that the sector would increase by a compound annual growth rate (CAGR) of 4.7 percent between 2015 and 2020, when the global market for food preservation techniques was expected to reach $582.8 billion. This includes revenues for all controlled intelligent packaging, preservation and shelf-life extension businesses for food products.

The development of modern food preservation techniques over the past century or so has allowed agriculture production to flourish for many grocery items, including eggs. According to the American Egg Board, the U.S. egg industry produced 255.87 million cases of 30 dozen eggs during 2017, a production level which totals more than 92 billion eggs, 59 percent of which ended up being shipped to retail environments. Through 2018, the per capita consumption of eggs among U.S. residents was expected to reach 278.9 eggs per person over the course of the year according to the online statistics portal Statista.

Today, Monday, April 2nd, marks the 82nd anniversary of the issuance of a seminal patent in the field of food preservation. While that patent may be specific to egg preservation, its inventor, Mary Engle Pennington, was a true pioneer of food preservation techniques to increase the shelf life of perishable food items.

This May, Pennington will be honored along with the rest of the 2018 class of inductees into the National Inventors Hall of Fame for her technological contributions to food storage and safety. With the anniversary of Pennington’s egg preservation patent upon us, we return again to our Evolution of Technology series to take a long view at the history of food storage and the contributions of this year’s Hall of Fame inductee, a pioneering scientist and the first female lab chief at the U.S. Food and Drug Administration.

The Pre-Pennington Period of Food Preservation

Evidence of ancient techniques for food preservation date back to as early as 12,000 BC, when cultures in the Middle East and Asia employed drying techniques to store food for longer periods. Salting, fermentation and pickling were other early methods employed to preserve food. Food preservation techniques through the 18th century usually reflected the climate and geography in which a particular culture lived; the hot climate of the Middle East lent itself to drying techniques while Scandinavian cultures made use of salting preservation techniques because of their access to the mineral.

In 1800, the French military leader and soon-to-be emperor Napoleon Bonaparte offered a prize of 12,000 francs to the person who could come up with a way to preserve food and keep his army fed. In 1810, this prize was awarded to French confectioner Nicolas Appert who developed the modern basis for what we know as canning. Theorizing that preservation techniques for bottled wine could work to store food, Appert came up with a process for putting food in glass bottles, sealing those bottles with a cork and wax and then placing the bottles in boiling water until the canned food was cooked.

Appert’s canning process would be greatly refined in 1864 when the famed French scientist Louis Pasteur came upon the discovery which would lead to pasteurization, a heating process designed to reduce the number of viable pathogens in canned food and beverages which is still in use today by the dairy industry. Pasteur’s process subjected food to less heat than Appert’s process, which allowed pasteurized foods to retain a better flavor after processing.

Mary Engle Pennington: The Mother of Modern Food Preservation

Mary Pennington was born in October 1872 in Nashville, TN, but her family would move to Philadelphia, PA, while she was still young to be closer to Quaker relatives. By 1892, at the age of 20, Pennington completed the requirements for a bachelor’s degree in chemistry with minors in botany and zoology at the University of Pennsylvania’s Towne Scientific School, now the university’s School of Engineering and Applied Science; the University of Pennsylvania only offered her a certificate of proficiency as it did not confer degrees on female students at that time. She would, however, earn a PhD from the University of Pennsylvania in 1895 when she was only 22 years old.

In the decade following her graduation, Pennington would work in research laboratories in fields including chemical botany, physiological chemistry and bacteriology at various institutions including the University of Pennsylvania, Yale University and the Women’s Medical College of Pennsylvania, the second medical academic institution established in the world to offer medical degrees to women. By 1905, Pennington began working with the U.S. Department of Agriculture’s Bureau of Chemistry, later the U.S. Food and Drug Administration, helping the agency develop educational materials for farmers handling raw milk to improve the quality of ice cream given to school children. Her exceptional work at that agency would lead to her being named the first head of the Bureau of Chemistry’s Food Research Lab which was created by the Pure Food and Drug Act of 1906. To help her chances of being hired at a time when female scientists did not hold prominent government jobs, her director at the USDA reportedly submitted a request to hire an “M.E. Pennington” to fill the Food Research Lab chief scientist role.

Under Pennington’s leadership, the Food Research Lab would provide pioneering research work supporting the idea that keeping fresh food at a constant low temperature would prevent spoilage and keep bacterial counts low. She also worked to define procedures for the safe handling of chickens at every point from the slaughterhouse to the consumer. She would continue in her civil service role until 1919, when she was hired by American Balsa to develop insulation for refrigeration units. In 1922, she started her own consulting firm and her career would continue to focus on spoilage-free methods of storing and shipping perishable food items, including eggs, poultry and fish, until her retirement in 1952.

On April 2nd, 1935, the U.S. Patent Office issued U.S. Patent No. 1996171, entitled Method of Treating Eggs and listing Pennington as the lead inventor. This is the patent for which her Hall of Fame induction is based. Typically, the National Inventors Hall of Fame will point to a single patent as the crowning achievement for which the inventor is being inducted. As with so many of her soon to be colleagues in the Hall of Fame, Pennington’s contributions to the field of food preservation go well beyond a single patent, or even a single line of research.

The ‘171 patent for which Pennington will be recognized claimed a process of treating egg material after separating from the shells and losing a portion of its initial carbon dioxide content, the process involving the dissolving of a quantity of carbon dioxide uniformly throughout the egg material by introducing carbon dioxide below the surface of the egg material to bring the carbon dioxide content of the material to at least the amount normally present in the corresponding untreated parts of fresh spring eggs. Pennington and co-inventor Arthur Thomas developed this process after determining that the high volatility of carbon dioxide, naturally occurring in freshly laid eggs, which diffused from egg shells and membranes negatively affected both the taste of the eggs as well as the egg’s ability to resist bacteria.


To say that modern refrigeration and food preservation techniques owe a great debt to Mary Engle Pennington is a rather embarrassing understatement that doesn’t capture the magnitude of her contributions. Throughout her life, she would be instrumental to the development of standards for ice-cooled refrigerator cars as well as construction and insulation for refrigeration units. In 1923, she founded the Household Refrigeration Bureau, which helped to teach U.S. consumers the importance of domestic refrigeration for food storage. In 1940, she would receive the Garvan-Olin Medal, the American Chemical Society’s top award for female chemists. When she died in 1952, she was still serving as the vice president of the American Institute of Refrigeration.


Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of

Join the Discussion

No comments yet.

Varsity Sponsors

IPWatchdog Events

Patent Portfolio Management Masters™ 2024
June 24 @ 1:00 pm - June 26 @ 2:00 pm EDT
Webinar – Sponsored by LexisNexis
August 22 @ 12:00 pm - 1:00 pm EDT
Women’s IP Forum
August 26 @ 11:00 am - August 27 @ 5:00 pm EDT
IP Solutions, Services & Platforms Expo
September 9 @ 1:00 pm - September 10 @ 2:00 pm EDT

From IPWatchdog