Food Engineering

Ultra-High Pressure Revolutionizes Seafood Processing

March 27, 2003
For more than two decades, Motivatit Sea-foods, Houma, LA, tried to reduce concerns about raw oysters, which can be tainted by naturally occurring Vibrio bacteria, a dangerous bacteria affecting shellfish.

"Every time someone gets sick from eating raw oysters, it has an adverse effect on the oyster industry," said Ernie Voisin, owner and president of Motivatit Seafoods, who processes 200,000 lbs. of in-shell oysters per week.

Voisin needed to destroy Vibrio bacteria without destroying the raw oyster's taste and texture. Voisin tried irradiation, which worked to a point, but has not been approved for shellfish by FDA. He also tried freezing, which changed the taste and texture, and quick cooling, reduced oyster's shelf life.

Voisin heard of research at the National Center for Food Safety and Technology (Summit, IL) with an ultrahigh-pressure (UHP) processing system from Flow International Corp. (Flow) generating pressures up to 135,000 psi to reduce bacterial loads.

"We ran about 30 tests with pressures ranging from 20,000 psi to 80,000 psi," said Voisin. "We found different pressure and time relationships killed bacteria while leaving oyster meat's taste and texture in perfect condition."

Using Flow's "Fresher Under Pressure" technology, Motivatit places oysters (50 to 60 lbs. per batch) into pressure vessels where isostatic pressure applies more than 30,000 psi. Processing vessels consist of a chamber and pump working together to generate and hold the ultrahigh pressure. Processing exposure is usually two to five minutes.

High pressure reduces harmful bacteria to non-detectable levels and destroys spoilage microorganisms. This results in not only safer seafood, but fresher, better-tasting product--"as good as the day it was harvested," according to Voisin.

In addition, Motivatit discovered a surprise benefit: UHP naturally shucks oysters. When placed under pressure, oysters release their muscle/shell connection, essentially shucking themselves. Once the UHP process is complete, oysters open without using shucking knives or hammers. Motivatit places a heat-seal band around the shell prior to processing, then ships the oysters to customers, where they snip the seal and serve.

"The high-pressure process shucks oysters perfectly -- and the meat is unchanged in taste or texture," notes Voisin. To date, Motivatit's single UHP unit processes about 20 percent of its total oyster volume.

Motivatit finds big savings in terms of labor as well. "Not only is it difficult to find good oyster shuckers, but hand shucking is very time consuming and easily damages oyster meat," adds Voisin.

Voisin says UHP also works on clams and mussels. "We tested high-pressure on clams and mussels reaching similar results. High pressure answers the two major problems for the oyster industry: killing Vibrio and shucking. We're very excited about this technology."

Flow International Corp., 23500 64th Ave. South, Kent, WA 98032 Web: www.flowcorp.com