Inactivation of Listeria innocua in milk and orange juice by ultrahigh-pressure homogenization.
The aim of this work was to evaluate the bactericidal efficacy of ultrahigh-pressure homogenization (UHPH) against Listeria innocua ATCC 33090 inoculated into milk and orange juice. We also intended to study the effect of inlet temperature on the lethality and production of sublethal injuries in this microorganism and its ability to survive, repair, and grow in refrigerated storage after UHPH treatment. Samples of ultrahigh-temperature whole milk and ultrahigh-temperature orange juice inoculated at a concentration of approximately 7.0 log (CFU per milliliter) were immediately pressurized at 300 MPa on the primary homogenizing valve and at 30 MPa on the secondary valve, with inlet temperatures of 6.0 +/- 1.0 degrees C and 20 +/- 1.0 degrees C. L. innocua viable counts and injured cells were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 degrees C for milk and after 3, 6, 9, 12, 15, 18, and 21 days of storage at 4 degrees C for orange juice. Both the inlet temperature and the food matrix influenced significantly (P < 0.05) the inactivation of L. innocua, which was higher in whole milk at the 20 degrees C inlet temperature. The UHPH treatment caused few or no sublethal injuries in L. innocua. During storage at 4 degrees C after treatments, counts increased by approximately 2 logarithmic units from day 0 to 9 in whole milk, whereas in orange juice counts diminished by approximately 2.5 logarithmic units from day 0 to 18.
Briñez
Wilfido José
WJ
Centre Especial de Recerca Planta de Tecnología dels Aliments, XiT, Departament de Ciencia Animal i dels Aliments, Facultat de Veterinària, edifici V, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
Roig-Sagués
Artur X
AX
Hernández Herrero
M Manuela
MM
Guamis López
Buenaventura
B
D000818:Animals; D001628:Beverages / Q000382:microbiology*; D002417:Cattle; D032084:Citrus sinensis / Q000382:microbiology; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D006874:Hydrostatic Pressure; D008087:Listeria / Q000254:growth & development*; D008892:Milk / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors