Heat Inactivation of E. coli O157:H7 in
Culture with or without Propolis
Overnight cultures of E. coli O157:H7 were diluted to
∼106 cfu/mL. One milliliter of adjusted culture was placed
in an aluminum can with an inside diameter of 18 mm
and height of 4 mm, immersed in a water bath and held at
57 ± 0.1, 60 ± 0.1 and 63 ± 0.1C for predetermined times
(Chung et al. 2008). For combination treatments, 1 mL of
E. coli culture was mixed with propolis (8.98 mg/mL) and
heat treated at 57 ± 0.1, 60 ± 0.1 and 63 ± 0.1C for predetermined
times. After heat treatment, the tested samples were
serially diluted and plated on TSA plates. The plates were
incubated at 37C for 24 h, and the surviving cell population
was counted and expressed as colony forming units
(cfu/mL).