Microbial Degradation of Seafood 57
cooked whole shrimps (Pandalus borealis) by 200% compared to air-packed
products (Sivertsvik et al., 1997).
SPOILAGE FLORA OF LIGHTLY PRESERVED PRODUCTS
Semi-preserved seafood products have undergone a very light preservation
process, such as salting, drying, smoking or marinating, leading to a fi nal
pH greater than 5.0 and a salt content below 6% in the aqueous phase.
Examples include smoked fi sh, carpaccio of salmon or trout, gravelax,
marinated anchovy fi llets, cooked products like peeled shrimps, preserved
in brine or in a modifi ed atmosphere etc. In terms of microbiology,
these products are very fragile. Because the raw material follows a long
preservation process with a good deal of handling, there is a signifi cant
risk of recontamination. Moreover, no step of the process involves the total
elimination of microorganisms and the fi nal product is often preserved for
several weeks at low temperature before being eaten. This allows some
psychrotrophic bacteria, which can spoil organoleptic qualities or present
a risk to human health, to multiply.
Two examples representative of this product category, cold-smoked
salmon and cooked peeled shrimps, have been discussed in this chapter
due to their economic importance in the European market.
Cold-smoked Salmon
In France, there is a long tradition of salting, drying and cold-smoking
seafood products, mainly salmon and herring. Nowadays, in the
industrialised countries, the aim of smoking is not so much to ensure a
long shelf life for the product but to give it a particular colour and taste.
With more than 20,000 tonnes produced each year, France has always been
the world leader in the production and consumption of smoked salmon. It
was originally a luxury product, eaten only on special occasions and made
by traditional methods. In recent decades, however, smoked salmon has
become an everyday food, available in supermarkets all year round and
produced on an industrial scale.
The production of smoked salmon involves different steps of fi lleting,
salting, drying and smoking at low temperatures (< 25°C) but each plant
has developed its own technology: salting by dry salt or by injection,
smoking with different wood essences and different smoke generators etc
(Duffes, 1999; Sérot et al., 2004; Knockaert, 2005; Cardinal et al., 2006). The
fi nal salt concentration is usually between 2.5 and 3.5% in the fl esh while
the smoke content, estimated by the quantity of total phenols, is between 2
and 20 µg/g. These products are generally sold sliced and vacuum-packed.
The producer is responsible for the use-by date, which is usually 3 to 6 wk
at 4°C in Europe. However, it is not uncommon to notice deterioration in
cooked whole shrimps (Pandalus borealis) by 200% compared to air-packed
products (Sivertsvik et al., 1997).
SPOILAGE FLORA OF LIGHTLY PRESERVED PRODUCTS
Semi-preserved seafood products have undergone a very light preservation
process, such as salting, drying, smoking or marinating, leading to a fi nal
pH greater than 5.0 and a salt content below 6% in the aqueous phase.
Examples include smoked fi sh, carpaccio of salmon or trout, gravelax,
marinated anchovy fi llets, cooked products like peeled shrimps, preserved
in brine or in a modifi ed atmosphere etc. In terms of microbiology,
these products are very fragile. Because the raw material follows a long
preservation process with a good deal of handling, there is a signifi cant
risk of recontamination. Moreover, no step of the process involves the total
elimination of microorganisms and the fi nal product is often preserved for
several weeks at low temperature before being eaten. This allows some
psychrotrophic bacteria, which can spoil organoleptic qualities or present
a risk to human health, to multiply.
Two examples representative of this product category, cold-smoked
salmon and cooked peeled shrimps, have been discussed in this chapter
due to their economic importance in the European market.
Cold-smoked Salmon
In France, there is a long tradition of salting, drying and cold-smoking
seafood products, mainly salmon and herring. Nowadays, in the
industrialised countries, the aim of smoking is not so much to ensure a
long shelf life for the product but to give it a particular colour and taste.
With more than 20,000 tonnes produced each year, France has always been
the world leader in the production and consumption of smoked salmon. It
was originally a luxury product, eaten only on special occasions and made
by traditional methods. In recent decades, however, smoked salmon has
become an everyday food, available in supermarkets all year round and
produced on an industrial scale.
The production of smoked salmon involves different steps of fi lleting,
salting, drying and smoking at low temperatures (< 25°C) but each plant
has developed its own technology: salting by dry salt or by injection,
smoking with different wood essences and different smoke generators etc
(Duffes, 1999; Sérot et al., 2004; Knockaert, 2005; Cardinal et al., 2006). The
fi nal salt concentration is usually between 2.5 and 3.5% in the fl esh while
the smoke content, estimated by the quantity of total phenols, is between 2
and 20 µg/g. These products are generally sold sliced and vacuum-packed.
The producer is responsible for the use-by date, which is usually 3 to 6 wk
at 4°C in Europe. However, it is not uncommon to notice deterioration in