2.2. Preparation and inoculation of minced chicken
Minced chicken was used as this allowed the use of small
packages that could be easily and uniformly inoculated. Raw
chicken breast fillets were purchased from a local supermarket. The
chicken was maintained at approximately 4 C during transportation.
On arrival at the laboratory, the chicken breasts were cut
into strips using a knife and minced using a 4 mm mincing screen
on a mincer attachment for a Kenwood Chef food mixer (Kenwood
Ltd., Hampshire, England). Sodium lactatewas added to some of the
chicken at a 2% w/w level. Portions of the minced chicken
(10 0.2 g) were weighed into either polyethylene/polyamide
vacuum pouches (Somerville Packaging, Lisburn, Northern Ireland)
or polythene bags and vacuum packaged in a vacuum packer
(Henkelman BV, ’s-Hertogenbosch, Netherlands). The oxygen
permeability of the vacuum pouches was 50 cm3/m2/24 h (at 1 bar,
23 C and 0% relative humidity), while the oxygen permeability of
polythene bags is typically 7000e8500 cm3/m2/24 h (at 1 bar, 23 C
and 0% relative humidity). To ensure that there was no interference
from endogenous microflora, all of the pouches of chicken were
sterilised by irradiation at 25 kGy as described in Patterson et al.