Scientists are reporting new evidence that a century-old food preservation technology, finding a new life amid 21st century concerns about food safety and nutrition, more than doubles the levels of certain healthful natural antioxidants in fruit. The effect, reported in Denver at the 242nd National Meeting & Exposition of the American Chemical Society (ACS), occurs as a bonus in addition to its effects in killing harmful bacteria, viruses and mold in food.
The technology, called high-pressure processing (HPP) involves subjecting food to 40,000-80,000 pounds of pressure per square inch for about 15 minutes. That's about five times the pressure that an African elephant would exert if it stood on a postage stamp. Applied evenly, however, the force in HPP does not squash the food—which can be fresh, processed, liquid or in other forms. The pressure does change the molecular structure of the microbes in food in ways that kill bacteria, molds and viruses. The technique also is known as "pascalization" in honor of the 17th century French scientist Blaise Pascal, famous for research on the effects of pressure on liquids. It differs from the more familiar thermal pasteurization process, which involves heating milk, beer and other foods to kill bacteria.
Carmen Hernandez-Brenes, Ph.D., presented results of the new study on HPP's effects on antioxidants in fruit. Her presentation was part of a symposium, entitled "Tropical and Subtropical Fruits: Flavors, Color and Health Benefits."
Hernandez-Brenes and colleagues set out to check the effects of HHP processing stability of a key group of antioxidants, termed carotenoids, using the pulp of avocado, papaya and mango subjected to HPP for three minutes. The researchers are with the Department of Biotechnology and Food Engineering, Technologico de Monterrey, Monterrey, Mexico.
HHP processing increased the concentration of total carotenoids in avocado and papaya by more than 50 percent. Individual members of this healthful family of chemicals increased by up to 513 percent, as detailed in Hernandez-Brenes' abstract, below. For reasons not yet clear, no increases occurred in the mango.
Their findings also support the possibility that the increases occur as a self-defense mechanism in fruit tissue. Hernandez-Brenes and collaborators detected viable genetic material called RNA after high-pressure treatment, and further work is underway to provide evidence that cells in the fruit had shifted into high gear to make more antioxidants to cope with the stress from HPP.