High Pressure Processing Renders Yogurt Sweet and Safe

Spanish researchers report that high-pressure processing (HPP) technology can effectively inactivate contaminants such as bacteria, molds, and yeasts in dairy foods like yogurt.

In a joint project sponsored by two Spanish dairy product companies, Tecnolat and Llet de Catalunya, the AZTI-Tecnalia Marine and Food Research Technological Centre studied the effectiveness of HPP in eliminating contamination from aerobic mesophiles, molds, and yeasts, which are largely responsible for the spoilage of fruit preparations in yogurts.

Jorge Lastra, Sci.D., an investigator with AZTI-Tecnalia’s food research unit, explained in an e-mail interview that HPP is like a cold pasteurization technique, which usually consists of subjecting food to a high level of hydrostatic pressure, up to 87,000 pounds per square inch for a few minutes. HPP takes several minutes, depending on the physical and chemical properties of the products, and requires that the food be sealed in flexible and water-resistant packaging, because pressure is transmitted by water, Dr. Lastra said.

Although HPP, also known as “pascalization” after French scientist Blaise Pascal, has been around in one form or another since the late 1800s, the technology is still being perfected for general use.

AZTI-Tecnalia reported that fruit yogurts subjected to HPP treatment at different intensities yielded total inactivation of the bacteria analyzed. “Once processed with high pressure, it was observed that the treated samples not only conserved their properties and characteristics of quality throughout their useful life–estimated to be three months–but also, sensorially, the products treated with high pressure tasted better than the traditional (heat-treated) samples,” Dr. Lastra said.

Commonly used decontamination and preservation techniques like pasteurization and sterilization involve changes in temperature, which can, in turn, produce changes in the food itself. “Thermolabile functional molecules may be modified, which can lead to vitamin and flavor losses and color and taste changes,” Dr. Lastra said. “With HPP, those thermolabile functional molecules may be preserved so sensorial and nutritional properties are less affected by the process while improving food safety.”