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From: Food Quality & Safety magazine, June/July 2011

A Pioneer in Thermal Death-Time Standards

C. Olin Ball used mathematical formulae to determine how much heat and time are needed to kill bacteria and keep food safe

by Lori Valigra

A Pioneer in Thermal Death-Time Standards

It may be common knowledge today that heat administered over time kills germs, including bacteria in food. But until the early 1900s, it was anyone’s guess for how long and at what temperature food needed to be cooked to make sure it was safe to eat.

That changed in the early 1920s, when several key discoveries were made, among them Charles Olin Ball’s (1893-1970) significant thermal death-time calculations. His formula methods to determine how long it takes to kill specific bacteria at a specific temperature brought such accuracy to food processing that even today his work remains a U.S. Food and Drug Administration (FDA) standard for calculating thermal processes in food preparation.

At around the same time, related research, aimed at producing a calculated lethal effect in bacteria, was performed by Willard D. Bigelow (1866-1939) and James R. Esty (1893-1954), who discovered the relationship of pH in food safety while Ball studied the function of pH in food process calculations. In addition, Dr. Esty and Karl F. Meyer, DVM, PhD (1884-1974), both of the University of California at Berkeley, studied the spores of bacteria and made important discoveries related to safe food processes.

“Ball was a true pioneer in developing organized microbial control in canned foods,” said Irving Pflug, PhD, emeritus professor of food science and nutrition at the University of Minnesota in St. Paul. “In 1920, his original work related to the amount of heat required for canning was certainly a quantum leap in the design and delivery of sterilization processes. In many ways, we haven’t done much to improve things since 1930 or 1935 as far as canning technology is concerned.”

Dr. Pflug described Ball, whom he knew, as a soft-spoken World War I veteran who was fairly conservative but had a lot of ability as a scientist. “When he came out of World War I, someone encouraged him to help solve some of the processes issues,” said Dr. Pflug. “In 1920, when he did all the calculations, all he had was a slide rule. It was before computers and calculators. Someone once said the advance he made in canning in the 1920s [under those conditions] would have won a Nobel Prize today.”

Getting Accurate Numbers

Ball’s discoveries continued earlier work by Nicolas Appert, a French confectioner who in 1810 developed a method for canning (see Food Quality, February/March 2011, “The Father of Food Preservation: Nicolas Appert invented techniques for long-term food storage”). But Appert’s work was in the early days of food preservation, when the details for canning still had to be worked out.

“Appert’s canning method was more of an art,” said Dr. Pflug. “People continued to experiment on how long to cook the food. And they became convinced they needed a more accurate way to handle processes and microbiology.”

A major advance came in 1895, when the William Underwood Company of Boston, America’s first canning company, noticed losses related to swollen and burst cans and asked the Massachusetts Institute of Technology (MIT) for assistance. Working on the problem, Samuel Cate Prescott, a chemist at MIT, focused on canned clams and discovered that they contained heat-resistant bacterial spores that had survived the canning process but that could be killed if they were processed at 250ºF for 10 minutes. The research, which was not patented, paved the way for Ball’s thermal death-time work; Bigelow’s work focused on Clostridium botulinum.

Until Ball came up with his formulae, scientists used graph paper to show thermal death time, reading numbers of temperature versus the time, typically in minutes, to kill organisms off of a paper chart, said Aaron Brody, PhD, president and CEO of Packaging/Brody Inc., a Duluth, Ga., consultancy. “Dr. Ball converted the chart into mathematical formulae. So it was possible to plug numbers into the formulae instead of reading them off a graph. He made it more accurate,” Dr. Brody said. Ball’s formulae turned Appert’s art of canning into a science.

While at Mead Corp. (now MeadWestvaco Corp.), Dr. Brody had the chance to work with Ball on sponsored research in another area of Ball’s expertise, aseptic canning. They worked together at New Jersey’s Rutgers University, where Ball headed the food sciences department, which now awards a student scholarship in his name. “Ball, along with William McKinley Martin, developed aseptic canning methods in the 1930s in which they sterilized a can and a food product separately and then brought them together in a sterile environment without retort operations [a compensation method for problems or mistakes],” Dr. Brody said. “Their canning systems were the first aseptic processes with evidence that separately sterilized packaging and product brought together in a sterile environment required no further heating.”

As Dr. Brody remembers it, Ball was very formal. “It was like dealing with someone from the 19th century,” he said. “He was very proper, very precise and conservative. He also was extremely conscious of food safety and of killing organisms to make sure they were dead.”

Dr. Pflug also remembers Ball for his work in heat penetration and aseptic canning. “He was an older gentleman in 1955 when I knew him, and he had built a couple of aseptic processing machines. He was canning in a steel room to pressurize the cans and decrease the heating time,” Dr. Pflug said. The room was more than 8 feet in diameter and was pressurized so people could work inside it. “The people took the same safety precautions as a diver,” he remembered. Ball was trying to improve the process for cooking meat, which heats slowly if canned as a solid piece. But when cut into smaller pieces, sealed, and heated, the canning was improved, he said. “The goal was better quality.”

Ball, a native of Abilene, Kan., earned a bachelor’s in mathematics before attending graduate school at George Washington University from 1919-1922. While at George Washington, he researched the sterilization of canned foods for the National Canners Association. The formulae for thermal death time, which became an FDA standard for calculating thermal processes, is still in use today. After graduate studies, Ball worked for the American Can Co. in Illinois and New York, earning 29 patents. From 1944-1946, he worked at Owens-Illinois Glass Co. before joining Rutgers University, where from 1949-1963 he was a professor and later chair of the food science department. Ball was also president of the Institute of Food Technologists from 1963-1964. He won the Nicolas Appert Award in 1947 and served as the first editor-in-chief of Food Technology magazine from 1947-1950. He died in 1970.

C. Olin BallThe formulae for thermal death time, which became an FDA standard for calculating thermal processes, is still in use today. After graduate studies, Ball worked for the American Can Co. in Illinois and New York, earning 29 patents.

Microbiology in the Mix

While Ball designed a safe process, his contemporaries —Dr. Esty, Bigelow, and Dr. Meyer—contributed microbiology to the mix to produce safe food. They studied resident microorganisms and how to kill them to preserve food. “Their work was important, another leg up on when Louis Pasteur discovered we had microorganisms,” Dr. Pflug said. Pasteur, in 1864, was the first to link spoilage and fermentation with microbiology (see Food Quality, April/May 2011, “A Key Figure in Food Safety: Louis Pasteur discovered that microorganisms spoil wine and milk”).

As Dr. Pflug sees it, while the technique of canning was improved by Ball’s contribution, Dr. Esty, Bigelow, and Dr. Myer studied what was required to process the food, specifically controlling microorganisms through pH. “By adjusting pH, you can better control for microorganisms,” he said.

Also contributing to the scientists’ advances were materials improvements made by industry. “You need to almost start in the early 1900s, when corporations made better tin plate so you had stronger containers, and rolled seams were improved so you had better quality,” said Dr. Pflug.

Bigelow was a professor of chemistry at Oregon State College who had also served as chief chemist and then director of the research laboratories of the National Canners Association. In his article, “Problems of Canning Operations,” published in the American Journal of Public Health in March 1918, Bigelow described heat and pH and their effect on bacteria. “The temperature necessary for sterilization varies through wide limits according to the nature of the product,” he wrote. “For the destruction of microorganisms, it is well known that a higher temperature is necessary for the spore form [of bacteria] than for the vegetative form. Again, the higher the acidity (within the range of the acidity of foods, for instance), the lower the temperature required for sterilizing the food.

“In general, spore-forming bacteria do not thrive as well in the more strongly acid foods as in foods of very low acidity. For both of these reasons the more strongly acid foods, such as tomatoes and the majority of fruits, can be sterilized at a lower temperature or in shorter time than foods of lower acidity.”

In the early 1920s, Bigelow, along with Drs. Esty and Meyer, researched heat-resistant bacteria. Drs. Esty and Meyer had been trying to better understand the organism Clostridium botulinum, because there had been several outbreaks and poisonings caused by that bacterium in canned foods that had been made in California. At the time, according to an article written in the University of California library publication Calisphere after his death, Dr. Esty was at the Hooper Foundation for Medical Research, University of California. The three men “helped to establish the methods and fundamental values in heat resistance of spoilage bacteria that form the basis of present-day scientific processing of canned foods,” according to Calisphere, which also noted, “Dr. Esty’s loss will be felt strongly by not only the West Coast members of the National Canners Association, but by the entire industry, for the contributions of his entire career had been of national import in the advancement of canning technology. His personal integrity had won for him the complete respect and confidence of canners, government officials, and fellow food scientists.”

Dr. Esty was born in Slatersville, R.I., in March 1893 and received his bachelor’s in chemical engineering from Rhode Island State College in 1914. He changed his major to bacteriology for his graduate work and earned a master’s and a PhD from Brown University in 1915 and 1918, respectively. He taught bacteriology at Brown from 1914-1916 and began working at the National Canners Association in January 1919 as a bacteriologist, developing a technique to determine the heat resistance of bacterial spores. He also conducted field studies to determine their source and made experimental packs inoculated with spore suspensions to determine sterilization time for various canned foods. His collaborations with Meyer and Bigelow, then director of research at the National Canners Association, resulted in pH and microbiological studies that affect canning processes today.

Valigra is a freelance writer based in Cambridge, Mass. Reach her at lvaligra@gmail.com.

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