Thermally-assisted high-pressure lifts quality of shelf-stable foods
FE: What's needed to commercialize UHP for sterilizing shelf-stable products?
Meyer: Two things must be done. First, develop the kinetic information necessary to file a petition with the FDA and USDA. To do that, we have to select the most heat and pressure-resistant strain of Clostridium botulinum. That work is underway with the Dual Use Science & Technology (DUST) Program 2000 headed by Dr. Patrick Dunne at the U. S. Army Natick Soldier Center in Natick, Mass. Dual use refers to developing the technology for both military and industrial applications. Second, we need commercial-size, inexpensive high-pressure vessels. Flow International Corp. (Kent, Wash.) is nearest to delivering that right now. They have a 215-liter vessel, which is very close to all the critical parameters for delivering a sterile product. They're leading with the technology, and just need to build a vessel to order.
FE: What time/temperature/pressure relationships are needed to sterilize a food product using high pressure?
Meyer: The process combines initial product temperature, pressure, the adiabatic heat rise caused by compression, and a minimum of two pressure pulses. The combination of initial product temperature and adiabatic heat must reach at least 105 degrees C. A typical test design would consist of initial product temperature at 90 degrees C, a 30-second pressure pulse at 700 MPa (a little more than 100,000 psi) to reach product temperature of 120-121 degrees C, a 30-second pause at ambient pressure, than a second 30-second pressure pulse at 700 MPa. The end product temperature is close to that used to achieve commercial sterility (i.e., kill C. botulinum spores) in a conventional retort process, but that's all the two processes have in common. Thermophilic spores will survive conventional retorting, but nothing survives the thermally-assisted high-pressure process. You get absolute sterility.