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High-pressure processing makes seafood safer

HPP technology can be an effective marketing tool if you learn what it's all about

HPP machines can cost up to $2 million, depending upon
    the size. - Photo courtesy of Virginia Tech
By Steven Hedlund
December 01, 2006

Burt Hite was way ahead of his time. In 1899, the West Virginia scientist discovered a means to pasteurize milk using high-pressure processing (HPP).

"The problem was," says Dr. Daniel Holliman, research coordinator of Virginia Tech's High Pressure Processing Laboratory in Blacksburg, Va., "the machine kept blowing up on him."

More than a century later, technology finally caught up with Hite's vision, and a number of companies worldwide are making food safer by subjecting it to intense water pressures, including oysters and American lobster. Foods treated with HPP didn't reach the commercial marketplace until 1990, when a Japanese company developed a way to use HPP on jam. By 2004, about 40 companies, half of them based in the United States, produced HPP foods, and there are even more today.

However, retailers, foodservice operators and especially consumers are relatively unfamiliar with HPP. Questions about the fundamentals of this processing technique are sure to arise as more products hit the marketplace. Now's the time to enroll your counter help and waitstaff in High-Pressure Processing 101. The more you teach them about HPP now, the less pressure they'll feel later.

Q. What does high-pressure processing do?

HPP is the technique of subjecting food to high hydrostatic pressures of 14,500 to 145,000 pounds per square inch, depending upon the density of the food. For example, jams and jellies are subjected to 14,500 to 58,000 psi, while in-shell oysters are subjected to 30,000 to 50,000 psi. The food is placed in a chamber and immersed in a pressure-transmitting liquid, usually water. A pump pressurizes the water, killing foodborne pathogens such as Vibrio , Listeria , Salmonella and E. coli and doubling or tripling the product's refrigerated shelf life, compared to an unprocessed product.

HPP "does not sterilize a product," says Holliman, "but it eliminates a majority of foodborne pathogens and spoilage bacteria."

Q. What are the benefits of HPP?

Unlike cooking, HPP raises the food's temperature only slightly and has little to no effect on its chemical make-up, so the food maintains its flavor, texture, appearance and nutritional content. Because no chemicals are removed or added, processors can market the food as "all natural."

In addition to making food safer, HPP "is a marketing tool," says Holliman.

Q. Does HPP damage food?

No. Because pressure is applied uniformly, the product maintains its form and shape.

For example, a grape is easily crushed when squeezed by hand, because pressure is applied unevenly. But a grape inside a water-filled plastic bottle remains intact no matter how hard the bottle is squeezed.

Q. What are the costs 
of using HPP?

Initially, HHP machines are expensive, running up to $2 million, Holliman acknowledges. Virginia Tech spent $650,000 for its 
17,600-pound machine, Avure Technologies' Quintus QFP 35L-600, in 2003. (Avure is a subsidiary of Flow International of Kent, Wash.)

But the cost of HPP machines is on the decline, and the machines are time, labor and energy efficient, so over time processors save money, says Holliman. It takes just a few minutes to pressurize a batch of food and just a few individuals to operate the machine, which requires only electricity and water.

Q. When did seafood processors begin using HPP?

In the late 1990s, Ernie Voisin, founder of Motivatit Seafoods in Houma, La., with the help of Flow, began using hydrostatic pressure to purge Gulf oysters of Vibrio vulnificus and separate the meat from the shell. Motivatit's HPP oysters are marketed under the Gold Band brand.

Joey Oysters of Amite, La., and Nisbet Oyster Co. of Bay Center, Wash., also market HPP oysters, processed using Flow's Fresher Under Pressure® technology.

Shucks Maine Lobster of Richmond, Maine, sells HPP, fresh, raw lobster meat, and Clearwater Seafoods of Bedford, Nova Scotia, markets HPP, frozen, raw lobster meat.

HPP can also be applied to blue crabs. The process "makes it a whole lot easier to pick the meat out of the shell," says Holliman.

Shellfish is ideal for HPP because the meat is protected by the shell and doesn't need to be packaged when processed, as with other foods.

Holliman isn't aware of any U.S. processors applying HPP to finfish, but he and his Virginia Tech colleagues are experimenting with that application.

"The meat has a tendency to look cooked" when subjected to HPP, he explains. "The temperature isn't elevated all that much, but the meat looks red or pink. The same happens with beef."

Retailers and foodservice operators must educate consumers about HPP and its effect on flesh color for HPP finfish to be marketed successfully, adds Holliman.

Q. What other foods are 
manufactured with HPP?

HPP is used to process numerous solids and liquids, including sliced deli meats, sausages, hot dogs, avocados, guacamole, salsa, jams, yogurt, fruit juices, apple cider and applesauce. Perdue and Hormel are among the food companies using HPP.

Acidic foods with a high water content are ideal for HPP, says Holliman.

Foods with a high air content, such as strawberries, are not, he notes. Proving the point, Holliman and his colleagues used their HPP machine to transform a marshmallow into a marble-sized ball and a Styrofoam coffee cup into a shot glass.

However, strawberries packaged in vacuum-sealed pouches and subjected to HPP "do just fine," says Holliman; he and his colleagues are experimenting with the fruit.

Q. Is HPP becoming more
popular?

Holliman is confident that the number of U.S. processors applying HPP to seafood and other foods will only increase, due to the technology's extensive list of benefits, particularly food safety.

"This summer's West Coast Vibrio outbreak probably wouldn't have occurred," he says, "if those oysters had been subjected to HPP."

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