an aliquot was plated on Oxford agar
and the plates were incubatedof sterile peptone water
was added. The bags were hand mushed briefly and stomached
(Stomacher 400, Seward) for a approximately 30 s. The number of
viable L. monocytogenes in the samples was determined by plating
aliquots (0.1 mL and 0.5 mL) of the stomached lettuce/peptone
water mixture onto separate Oxford plates, containing Oxford Listeria
Selective Supplement, and incubated at 35 ± 2 C for 24 ± 2 h.
The resulting colonies were counted and the CFU/g was calculated
taking sample size and dilution into account.