The energy released during cavitation has great potential to improve food safety by destroying microorganisms and pathogens, as well as detecting foreign material and making it easily removable.
The first application of cavitation in microbial inactivation was reported in the late 1920s (Harvey & Loomis, 1929); however, the overall lethal effects were limited to achieving sterilization. Rapid advances in cavitation-related technologies in recent decades have rekindled interest in its application for microbial inactivation.
Recently, there has been a trend towards non-thermal technologies as an alternative to heat treatment for food processing, mainly due to the preservation of the sensory qualities of the product, which are typically heat-sensitive.
Riding this wave, hydrodynamic cavitation technology has an advantage in pasteurization and dairy preservation through the elimination of microorganisms and enzymatic inactivation.
For example, the combined effect of hydrodynamic cavitation/heat treatment on total viable counts and psychrotrophic bacteria in raw, pasteurized, and sterilized milk resulted in a 1-2.1 log cfu mL-1 reduction in total viable counts and psychrotrophic bacteria for all three types of milk samples up to 6 days of storage.
This demonstrates that hydrodynamic cavitation with closed-loop reactors can be used effectively for homogenization and microbial inactivation in untreated milk.
In the case of hydrodynamic cavitation, the percentage of microbial reduction was a function of the number of cavitation events per unit volume, the inlet pressure to the cavitation element, the geometry of the cavitation plate, and the volume of vapor generated.
The highest volume of vapor and microbial load reduction (up to 88%) was achieved with a monocentric rectangular bore hydrodynamic cavitation plate.
In the case of ultrasound, an inactivation efficiency of 95% was achieved; however, it required the addition of CO2, a higher applied power and a treatment time of 10 minutes.
Hydrodynamic cavitation combined with a suitable gas would therefore be even more effective for commercial application.
