Major achievements in HURDLETECH

Hurdle technology (including minimal processing) to ensure quality and safety of convenience seafood

Major achievements in 2006

The food safety risk of rehydrateted salt-cured cod is very small due to the short sensory shelf life, as long as the fish is stored at 4C or below, is not vacuum packed, and the contamination level of Listeria spp is below app 20 cfu/g. However, vacuum packing increases the food safety risk, because it extends the sensory shelf life of rehydrated salt-cured cod extensively, but does not inhibit growth of Listeria spp. The preservatives sodium benzoate and sodium sulphite do however inhibit Listeria spp growth sufficiently to minimise the food safety risks. Moreover, initial studies in stomach acid model system have indicated that L. innocua has a lower ability to survive at stomach acid conditions when first exposed to high salt concentration.

Concerning Lightly Preserved Fishery Products (LPFPs), 28 of the 29 L. monocytogenes strains from the HURDLETECH collection were determined as virulent by a mouse test. A qRT PCR assay has been successfully developed as an alternative tool to assess virulence that will be used to determine the effect of smoke on virulence. The effect of different technological parameters (salt, smoke, partial freezing, vacuum packaging, and storage temperature) on L. monocytogenes growth has been studied, in situ. Finally, antilisterial synergy between different phenolic compounds has been demonstrated.

Different molecular tools (PCR-ITS profiles and PCR-RFLP) have been developed to identify the 52 protective cultures (PC) strains selected in the last period. 16S rDNA sequencing of seven PC have led to original species (Leuconostoc gelidum/inhae, Lactococcus piscium, Carnobacterium alterfunditum and Lactobacillus fuchuensis. Mechanism of inhibition was determined and safety aspects of those PCs provided. In situ effects of PCs against pathogenic strains have started.

The antimicrobial effect of chitosan coated onto LPFPs has been demonstrated on inoculated L. innocua, however, the effect on endogeneous flora is very low. The addition of plasticizers increased the mechanical properties of the films and did not interfere with the antibacterial activity of chitosan, which greatly inhibited most bacterial groups tested in vitro. Some hydrolysates provided by PROPEPHEALTH showed an inhibition capacity of the growth of several strains from HURDLETECH collection.
Finally, Pulsed Light has been demonstrated as a potential technique to reduce the flora (both inoculated L. monocytogenes and endogeneous flora) of cold smoked salmon (CSS) (1 Log reduction) and surimi (2.5 Log) without any negative change in physico-chemical properties.

Projectleader HURDLETECH
Dr. Francoise Leroi