Inactivation of Escherichia coli K-12 Exposed to Pressures in Excess of 300 MPa in a High-Pressure Homogenizer

Abstract

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.

Inactivation of Escherichia coli K‐12 in Apple Juice Using Combination of High‐Pressure Homogenization and Chitosan

“…Although heat was removed using chilled water circulation around the homogenization valve (5 °C), the temperature increase was proportional to the homogenization pressure (Figure 5). A quadratic relationship ( R 2 = 0.97; P < 0.05) between pressure and temperature was observed, as reported by Taylor and others (2007). Using the D 58 (4.04 min) and z values (5.4 °C) reported by Taylor and others (2007) for E. coli K‐12 and the residence time of less than 20 s, the equivalent thermal destruction of E. coli K‐12 at observed process temperature was calculated using thermal process calculation (Singh and Heldman 2003) and is presented in Figure 5.…”

High-pressure homogenization of orange juice to inactivate pectinmethylesterase

“…Nevertheless, a few studies have been conducted using homogenizers for microbial and, or enzyme inactivation purposes. Taylor, Roach, Black, Davidson, and Harte (2007), for instance, observed a significant reduction of Escherichia coli K-12 in sodium chloride solutions (0.9%) in the range of 100 to 250 MPa using a high-pressure homogenizer. Pathanibul, Taylor, Davidson, and Harte (2007), on the other hand, using similar pressure conditions, reported an inactivation of around 5.5 and 6 log 10 (CFU/mL) of E. coli K-12 and Listeria innocua, respectively, inoculated in apple and carrot juices.…”

Use of high pressure homogenization as a mean to control the growth of foodborne moulds in tomato juice

“…High Pressure Homogenization (HPH) is an emerging non-thermal technologies that has demonstrated capability to inactivate various types of bacteria without significant loss of product quality (Bevilacqua, Cibelli, Corbo, & Sinigaglia, 2007;Bevilacqua, Costa, Corbo, & Sinigaglia, 2009;Taylor, Roach, Black, Davidson, & Harte, 2007); in addition, this treatment provides improved product stability, prolonged shelf life. Several authors (Desrumaux & Marcand, 2002;Hayes & Kelly, 2003;Sandra & Dalgleish, 2005;Zamora, Ferragut, Jaramillo, Guamis, & Trujillo, 2007) have studied Ultra High Pressure Homogenization (UHPH) application to milk.…”