2. Materials and methods
2.1. Preparation of bacterial culture
In order to decide which strain should be selected for this study
a pre-study was performed on six strains of L. monocytogenes and
2 strains of L. innocua. All strains were obtained from IFL-collection
after isolation from product or processing environment during cold
smoking. The strains were cultivated overnight in Tryptic Soy Broth
supplemented with 0.6 g Yeast Extract/100 g (Difco) at 35 C and
subcultured twice. All these strains have been compared by
a genetic typing technique using pulsed-field gel electrophoresis
(Gudmundsdottir et al., 2005). The following strains were tested for
the efficacy of HPP on reducing the bacterial number: L. innocua,
strains EU2173/E-34 and EU2172/E-33; L. monocytogenes, strains E1,
E5, H-01-170-2, L-327, L-435 and L-462.