October 16, 2007
Aseptic processing: The science of freshWEST LAFAYETTE, Ind. -
As a professor of food science at Purdue University, he spent years perfecting the primary method that today allows many juices and other liquid foods to be safely processed, packaged and shipped around the world in mass quantities.
For this discovery and work related to the process - called aseptic processing - Nelson is being awarded this year's World Food Prize. Regarded as agriculture's equivalent to the Nobel Prize, the World Food Prize recognizes an individual who has improved the quantity, quality and availability of food in the world.
Nelson and his technology have helped do all three. But what is aseptic processing, and what is the science behind it?
Mark Morgan, an associate professor of food science, said aseptic processing is a method to safely process food before putting it into a similarly sterile container. Nelson not only helped develop this method, but upgraded it to the point at which companies were able to produce mass quantities of safe, shelf-stable food products that have provided nutrition to millions of people, according to the prize committee.
"In aseptic processing, you sterilize the food, then you sterilize the package, and you put them together in a sterile environment to create a safe, ready-to-eat, shelf-stable product that can be transported, usually without refrigeration," Morgan said. "For most food products, you get better quality because it's been processed less, but it's just as safe."
When a food product is aseptically processed, it passes through a very thin pipe where it is rapidly heated to kill pathogens before being quickly cooled. The short heating time sufficiently kills germs but minimizes the quality degradation that heating invariably causes.
The method differs from canning and other traditional processing, wherein additional energy is required to heat and sterilize the larger volume of prepackaged food.
"Even the food in the middle of the can has to be heated, which takes significant time and energy," Morgan said.
"I remember when pudding used to come in cans, for example. It always had a distinctly cooked taste. Now, using aseptic processing, pudding is more quickly processed and stored in plastic containers. It tastes better, fresher."
Although aseptic processing existed when Nelson began his pioneering work, it was just beginning. He figured out how to apply the process on a large scale and how to put the product into a sterilized container in a sterile atmosphere. This is done in a sealed compartment that keeps out pathogens by using pressurized, already-sterilized air, Morgan said.
Nelson also discovered an efficient way to sterilize very large containers, such as the 300- to 500,000-gallon containers used in oceangoing vessels that transport juices around the world. And he helped develop the individual sealed bags that effectively store sterile foods, from yogurt to wine.
Morgan and Nelson continue to work on new methods to sanitize processing equipment, such as using a gas called chlorine dioxide that they have shown can effectively kill pathogens without leaving unsafe byproducts or residues.
This process could save time and energy; large tanks are typically treated with steam, which must be heated and takes longer to work than chlorine dioxide. Morgan said he sees this process being used in the future, and a company he works with will soon test its commercial feasibility.
Aseptic processing works well for liquids and semi-liquid foods like pudding, but it is more difficult for solid or chunky foods.
"You can't exactly put a ham through a pipe," Morgan said.
The challenge with solid foods is to find a way to sterilely package them. With chunky foods like soups, the different pieces of the food mixture are heated unevenly, taking varying time to pass through a pipe. These are critical variables that are difficult to fine-tune in a large-scale processing system, Morgan said.
Scientists at Purdue and elsewhere also are working to develop novel technologies for sensing pathogens, which could allow manufacturers to quickly discover contamination.
"For any processing method, the better sensors we have for detecting pathogens, the better we can design the process to eliminate them," Morgan said.
The World Food Prize will be awarded to Nelson at 6 p.m. Thursday (Oct. 18) at the Iowa State Capitol Building in Des Moines.
Writer: Douglas M. Main, (765) 496-2050, firstname.lastname@example.org
Sources: Mark Morgan, (765) 494-1180, email@example.com
Philip Nelson, (231) 539-8322, firstname.lastname@example.org
A publication-quality photo is available at https://news.uns.purdue.edu/images/+2007/morganaseptic.jpg
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