2.6. Effect of ListShield™ on experimentally contaminated cheese
A hard, pasteurized cheese was obtained from a dairy producer
in Colorado. A 600 g portion of cheese was contaminated on all
surfaces with ca. 1 104 CFU/g of cheese and loosely covered. The
bacteria were allowed to colonize the sample for 60 min at room
temperature. The cheese sample was divided into two 300 g portions
and were treated at a rate of 1 mL/100 g of cheese; the control
group was treated with PBS and the test group was treated with
ListShield™ at a rate of 1 108 PFU/g of cheese. The samples were
covered and incubated for 5 min at room temperature. Three 25 g
samples were then cut from each group, placed into separate sterile
bags, and stomached for approximately 30 s with 225 mL of sterile
peptone water. The remaining cheese was moved to 4 C for storage
and sampled again, in triplicate, at 24 h and 96 h post treatment.
The number of viable L. monocytogenes in the samples was determined
as above.