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Novel inactivation methods are needed to control the spread of foodborne viruses responsible for nonbacterial gastroenteritis worldwide. The advent of high-pressure homogenization combining high pressure, shear stress, and cavitation provides the opportunity to evaluate this technology for viral inactivation in fluid foods under continuous processing conditions. Our objective was to evaluate murine norovirus (MNV-1) and MS2 coliphage (single-stranded RNA) as human enteric virus surrogates for their susceptibility to a novel high-pressure homogenization process for application in commercial settings. Experiments were conducted in duplicate with MNV-1 and MS2 coliphage in phosphate-buffered saline, using homogenization pressures of 0, 100, 200, 250, and 300 MPa (the maximum achievable by the homogenizer), resulting in exposure temperatures of 24, 46, 63, 70, and 75 degrees C, respectively, for <2 s. Only homogenization pressures of 300 MPa at 75 degrees C showed inactivation of approximately 3 log PFU for MS2 from an initial approximately 6 log PFU. Also, MNV-1 showed inactivation of approximately 0.8 log PFU at 300 MPa. Further studies are warranted to validate this inactivation process, which can retain the sensory and nutritional value of fluid food and shows promise for application in industrial environments.

The association of triclosan (TCS), a widely used hydrophobic compound, to the bovine casein micelle is investigated in this study. The use of high-pressure homogenization (HPH) at 0, 100, 200, and 300 MPa was introduced as a method for the dissociation of casein micelles in a skim milk/ethanol solution (1: 1, v/v) in the presence of TCS at 20, 80, and 160 mg/L where ethanol evaporation served as the final step for TCS association to caseins. The majority of TCS (over 80%) was associated with the caseins regardless of initial TCS concentration or applied pressure. TCS association to caseins was enhanced by 30% with continued pressurization to 300 MPa. Micellar dissociation and reassociation was found to be an irreversible process as evidenced by microscopy images. Pressurization to 300 MPa resulted in the formation of an integrated protein network of casein proteins and noncovalently linked whey proteins where the solubility of TCS was enhanced up to 40 times its reported water solubility at the highest initial TCS level of 160 mg/L. Reformed micelles exhibited Newtonian flow behavior at all pressure levels. This study provides evidence for the solubility enhancing quality of TCS through the solvent-mediated pressure/shear-induced dissociation of casein proteins.

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Homogenization is used widely in the dairy industry to improve product stability and quality. High-pressure homogenization (HPH) of fluid foods up to pressures of 300 MPa has demonstrated excellent potential for microbial inactivation. Microbial inactivation can be enhanced during HPH with the inclusion of antimicrobial compounds. Escherichia coli K-12 cells, grown statically or in chemostat, were exposed to HPH processing pressures of 50 to 350 MPa in the absence or presence of the antimicrobial nisin. Valve temperature was regulated by a water bath and pressure, and temperature data were recorded continuously after process initiation. Survivors were enumerated via plating on nonselective growth media. Pressure and temperature at the valve outlet port exhibited a quadratic relationship (R(2) = 0.9617, P < 0.05). Significant HPH-induced inactivation of the gram-negative microorganism was observed in the range of 100 to 250 MPa. Above 300 MPa, heat was the main factor promoting microbial inactivation, regardless of whether cells were grown in chemostat or statically. Chemostat-grown cells were significantly (P < 0.05) more resistant to HPH processing than were statically grown cells. Data indicate potential synergistic effects of nisin and HPH on the inactivation of bacterial contaminants. This study represents the first report of inactivation of a bacterium with HPH pressures in excess of 300 MPa in the presence and absence of an antimicrobial.