Raw Oysters Get a Squeeze
High Pressure Processing (HPP) is a food processing method that uses pressure instead of heat to make foods safer, eliminating the majority of harmful bacteria while preserving the food’s natural nutrients, texture, taste, and appearance. The concept of HPP was developed more than 100 years ago, but it was only in the last 15 years that the technology became feasible as a safe technique for processing food.
Virginia Tech began its research three years ago when George Flick, University Distinguished Professor of food science and technology, made arrangements to acquire and house the $800,000 high-pressure machine, which weighs nearly 10 tons. The commercial-size unit allows the department to work directly with commercial food manufacturers interested in using the technology.
Dan Holliman, M.D., a research scientist in food science and technology, is a key member of the HPP research group and has studied the effect of high pressure on a variety of different foods, particularly oysters. Oysters are problematic because many people like to eat them raw. Oysters gain nutrients by filtering sea water, and as they filter this water, they also may accumulate water-borne pathogens such as Vibrio parahaemolyticus and Vibrio vulnificus. Raw oysters, unlike steamed or fried oysters that are cleared of harmful bacteria by high levels of heat, have the potential to cause serious illness. How can raw oysters be processed without altering their characteristically slippery look, feel, and taste?
Oysters can be processed using HPP. The treatment doesn’t affect the taste or feel but slightly alters the look, actually making them appear more plump. HPP also releases the shell of the bivalves, saving time and labor in the oyster shucking process. HPP oysters are now commercially available.
Holliman is also studying the effects of HPP on viruses common in oysters outside the United States such as the Norovirus and Hepatitis A. His goal is to develop the parameters, temperature, time, and amount of pressure needed to kill these viruses as well as the most common bacterial pathogens.
HPP also has applications in the development of vaccines for certain bacterial infections. Since HPP deactivates, but doesn’t physically destroy bacteria, the bacteria is still present within the treated substance. Holliman comments that the technology has the potential to be used to deactivate bacteria while leaving its’ immunologic markers intact – this deactivated bacteria can then be used to develop vaccines. Holliman is seeking the funding necessary to expand his projects in this area and to eventually develop promising new vaccines.