Continuous high pressure processing of liquid foods
Cavender, George Armstrong
MetadataShow full item record
While the effects of high pressure on the safety and quality of food have been studied occasionally for over one hundred years, it is only recently that the widespread study and use of the technology has become feasible. One of the more interesting and least studied type of high pressure processing is continuous high pressure processing (CHPP), sometimes referred to as "high pressure homogenization" or "dynamic Pascalization." The current work examines the history and work in the field to date and goes on to investigate the effects of various CHPP systems on the microbial, physical, structural and sensory properties of liquid foods. Because the high shear conditions created in the release component(s) of a CHPP system generate significant heat, it has often been difficult to separate the anti-microbial effects of pressure and shear from those of temperature, particularly with regard to vegetative cells. By using a modified valve with inline cooling, the instantaneous temperature rise was dramatically lessened, showing that only a modest amount of inactivation results from the increased pressure and shear. The work further explains the effects of microfluidization, a type of CHPP system based upon a fixed geometry pressure release component, on ice cream mixes and the ice creams made from those mixes. Microfluidization is shown to effect changes in the texture, melting properties and viscosity of finished ice cream and to thereby improve the sensory characteristics of the same. It is later shown that the changes are evoked on a microstructural level, with visible differences apparent in electron micrographs, and that these changes affect the particle size distribution, apparent viscosity and dynamic rheology with treated samples showing more uniform particle size, significantly higher viscosity and more solid-like behavior than untreated samples.