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Crowning Achievements In Bulk Aseptic Storage

October 3, 2007
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Phil Nelson once was crowned Indiana’s Tomato King. This month, the World Food Prize recognizes his achievements in bulk aseptic storage.

Philip E. Nelson, William Scholle Endowed Chair in Food Processing, Purdue University, West Lafayette, IN. Source: Purdue University.


Ingenuity is a distinctly American trait, and on October 15, the World Food Prize will recognize the inventiveness of Philip E. Nelson in advancing aseptic processing and packaging.

Nelson is the twelfth American to share or win the prize outright since it was created in 1986. The $250,000 prize recognizes individual contributions to improving global food quality and availability. In naming Nelson this year’s recipient, the award committee cites his problem-solving abilities in developing bulk storage tanks, bag-in-box containers and special fitments, valves and filters for aseptically processed fruits and vegetables, as well as his ingenuity in forming partnerships with Scholle Corp., Fran Rica Manufacturing, Enerfab Inc. and others to turn his ideas into commercial systems. His research and development efforts profoundly impacted the tomato and orange juice markets in particular, but their global impact attracted the committee’s attention. Sterile packaging has been instrumental in advancing human nutrition in the Philippines, India, Pakistan and other nations and plays an expanding role in meeting critical needs for potable water and other necessities in crisis situations such as 2004’s Southeast Asian tsunami and 2005’s Hurricane Katrina.

As an Indiana farm boy, Nelson worked at his family’s tomato cannery while nurturing an interest in horticulture, which led to a 4-H award and the official title of Tomato King. After earning a BS degree in general agriculture at Purdue University, he returned to the family farm and served as canning plant manager in the late 1950s. When the plant closed in 1960, Nelson accepted a paid assistantship in horticulture at his alma mater, writing a PhD dissertation on flavor volatility in canned tomatoes.  

Mark Morgan works with the pilot-scale chlorine-dioxide gas unit for sterilizing fruits and vegetables at Purdue University’s Department of Food Science pilot plant. Source: Tom Campbell, Purdue University.

FE: It’s estimated 90% of the global tomato crop is aseptically processed and packed, resulting in minimal waste. What was the situation in the 1950s?

Nelson: At that time, there were more than 200 canneries in Indiana, and a lot of the waste ended up in the can. Everything was put up bright, that is, unlabeled. At the end of the season, you’d have a glut of juice and not enough puree or vice versa. The result was waste.



FE: When you began work on aseptic systems, what was the state of the technology?

Nelson: Tetra Pak already was applying it successfully in small consumer packages. I wanted to do it in bulk and put a big bulge in the supply line so processors could determine how much to remanufacture as sauce, juice, ketchup and other products throughout the year, based on market demand. That required a sterile storage tank.

Until the FDA approved hydrogen peroxide for package sterilization in 1982, aseptic technology wasn’t feasible in the US, with the exception of the Dole Canning System, developed 1948. They were putting pudding in cans sterilized with steam. About 20 units were in operation around the country, but it didn’t involve large containers.

I wrote to 10 different companies about fabricating aseptic storage tanks, and the only one willing to roll the dice was Bishopric Products (now Enerfab Inc.) in Cincinnati. They made lined tanks for the brewing industry. I had them make five 100-gallon tanks, three lined with epoxy and two fabricated from stainless steel. We flooded the tanks with different chemical sterilants and found that etches in stainless steel were a problem. The coated carbon steel tanks were easier to sterilize and cheaper, too, though they couldn’t tolerate high heat. We then began fabricating larger tanks, up to 25,000 gallons. I couldn’t find any aseptic valves or filters to work with the tanks; we developed those components ourselves.



FE: Were commercial partnerships unusual at the time?

Nelson: Absolutely. My research director said I shouldn’t be taking industry money, but without it, it would have just been a nice university project that never had a commercial impact. I was doing the design work, and they would do the fabricating and scale up. It was a great example of a university and industry working together.

Today there really isn’t a debate about such partnerships. Universities have their own lawyers to write patent licensing agreements. It’s the only way to develop technology that will be commercially useful.



FE: Besides tomatoes, what other aseptic challenges did you address?

Nelson: We were looking at processing apple, grape, mango, banana-a lot of high-acid fruits and vegetables. We made a banana puree that was a beautiful pink. Like every problem, it wasn’t one factor; there were multiple ones. Heat treatment was too high, and there were trace elements in the fruit that were discovered with a mass spectrometer I had access to.

We tend to think if a little heat is good, more is better, so refinement of heat sterilization and rapid cooling processes was one focus of our work. Reducing temperature down to ambient very quickly is important with most foods for retaining flavor and nutrients.



FE: When did your work with orange juice begin?

Nelson: In the 1980s, Tropicana wanted to sell orange juice that was not from concentrate. We didn’t think it was possible to process it aseptically because there were enzymes in the fruit that survived heat treatment, but we accepted the challenge. We weren’t successful in making orange juice shelf stable, but refrigeration to keep the temperature below 40º F has proven to be a useful hurdle technology. If there is an issue, we may have to use the juice quicker, but we don’t lose the whole tank.

The epoxy-lined tanks are enormous. One of the transport ships we helped develop can carry 8 million gallons of juice in 16 half-million gallon tanks. The land-based tanks contain up to 1.8 million gallons each. They’re six stories tall and about six stories wide. It’s beyond my imagination.



FE: What types of technical and scientific expertise have been brought to bear in developing aseptic technology at Purdue?

Nelson: Microbiologists, chemists, packaging engineers and mechanical engineers are part of the team. When we started offering aseptic workshops 25 years ago, I had to bring in academics from all over the US to conduct them. Today, it’s all Purdue people.



FE: In recent years you’ve coauthored research papers on using chlorine dioxide gas and ozone gas as decontaminants for produce and food-contact surfaces. Which treatment has the greatest potential?

Nelson: Ozone gas has some uses, but in our studies, chlorine dioxide is a quicker and more effective sterilant. Not only can it be used as an antimicrobial on the surfaces of fresh produce, chlorine dioxide also can sterilize tanks, processing lines and other equipment. We have a joint USDA project with Iowa State University to sterilize a meat line.

I serve an advisory role. Dr. Richard Linton heads the project, along with Dr. Mark Morgan. Our approach is to develop a pilot application and bring industry right along with us. Enerfab and ClorDiSys Solutions Inc. are helping fabricate an industrial tunnel system to apply chlorine dioxide gas to sterilize products without heat. The challenge is optimizing the system to kill pathogens without adversely affecting the quality of the product.



FE: Despite the development work, aseptic remains niche technology in the US. Does that disappoint you?

Nelson: Aseptic is slowly taking root. Food industry interest is on the upturn: We’re turning people away from our workshops now. It’s encouraging.

Equipment manufacturers are centered in Europe because we got into aseptic so late, and we have a highly developed refrigeration infrastructure. But aseptic is going to be a large factor in China’s food supply. It helps preserve food for both domestic distribution and for export. Developing countries have shifted from tin tanks, which were too expensive, to inexpensive bulk bag-in-box technology. That will enable them to grow their economies and buy nonfood US goods. Everyone wins.



FE: You were crowned Tomato King at the Indiana State Fair because of four-dozen perfect tomatoes grown for a 4-H competition. What constitutes a perfect tomato?

Nelson: When you see it, you know it: small scar tissue, perfect roundness, a bright red color. After winning, I had lunch with the governor, got a gold watch and drove around the Indy 500 track at the Brickyard. I was only 15. It was a big deal.

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