The use of hydrodynamic cavitation resulted in 100% elimination of Escherichia coli in milk samples inoculated with 1 × 104 and 1 × 106 cfu mL-1 of E. coli, 99% and 99.14% elimination of Listeria monocytogenes in milk samples inoculated with 1 × 104 and 1 × 106 cfu mL-1 of L. monocytogenes, respectively, while in the case of milk samples inoculated with 1 × 104 and 1 × 106 cfu mL-1 of Pseudomonas fluorescens, shorter residence times were required to achieve 100% elimination.
Hydrodynamic cavitation in combination with heat treatment (63 °C) resulted in the inactivation of Listeria cells in nonfat milk; however, the rate of inactivation decreased with increasing fat content
After treatment with hydrodynamic cavitation, a reduction of E. coli and Saccharomyces cerevisiae > 99% (in both saline and UHT milk suspension), a 72% reduction of Lactobacillus acidophilus in saline, and an 84% reduction of L. acidophilus in UHT milk were observed compared to the initial inoculation level of 1 × 10^4 cfu mL−1.
Scanning electron microscopy suggested that cavitation causes extensive external and internal damage to all three microbes tested, with lipopolysaccharide vesicles forming on the E. coli cell wall, leading to fragmentation following emulsion formation. When treated at rotor speeds of 3,000 and 3,600 rpm (hydrodynamic cavitation), skim milk showed a reduction of 0.69 and 2.84 log-cfu cycles (Clostridium sporogenes anaerobic putrefactive 3,679 spores).
In addition, hydrodynamic cavitation was found to be effective in reducing the biofilm-forming ability of various spores (Geobacillus stearothermophilus, Bacillus licheniformis and Bacillus sporothermodurans) on stainless steel surfaces.
This low-speed technology can be used for the decontamination of milk from heavy metals without compromising its physical, chemical and microbiological properties.
Hydrodynamic cavitation has been shown to be highly effective in reducing microbial load.
Its application in combination with traditional industrial methods such as heating, or alone, will be a more efficient and cost-effective system for improving food quality and safety.
