One way of achieving this reliably would be to introduce a heating
step. Following an outbreak of salmonellosis in the UK associated with a
salami stick product imported from Germany, the production process
was changed to incorporate a final pasteurization step without adverse
effects on sensory quality.
Nam, the Thai fermented sausage, differs in several respects from
European fermented sausages. It is a low-fat product which is subjected
to a short fermentation and is not dried. It is also wrapped in water-
impermeable plastic material or, traditionally, banana leaves. As the
fermentation proceeds and the pH drops the moisture is expelled but is
trapped within the packaging giving the consumer an indication of the
age of the product. It is not always stored chilled and its largely
anecdotal association with food poisoning has prompted test marketing
of irradiatednamin some areas of Thailand.
9.9 Fermented Fish
The term fermented fish is applied to two groups of product, mostly
confined to East and Southeast Asia: the more widely known fish/salt
formulations such as fish sauces and pastes, and fish/salt/carbohydrate
blends. Strictly speaking, only in the latter case is the description
‘fermented’ fully justified. Microbial action in the production of fish
sauces and pastes is slight if not insignificant and the term is being used in
its looser, non-microbiological, sense to apply to any process where an
organic material undergoes extensive transformation.
In many areas where they are produced, fish sauces and pastes are the
main flavour principle in the local cuisine and provide a valuable
balanced source of amino acids. The names of some fish sauces and
pastes and their countries of origin are given in Table 9.8.
Fish sauces and pastes are usually made from a variety of small fish
which are packed into tanks or jars with salt usually at a ratio of around
three parts fish to one part salt. This is more than sufficient to saturate
the aqueous phase, to produce anawbelow 0.75 and arrest the normal
pattern of spoilage. The only organisms likely to be able to grow under
such conditions are anaerobic extreme halophiles. Although there have
been recent reports of isolations of organisms such as the proteolytic
Halobacterium salinariumfrom fish sauce, their importance remains to be
established since earlier work has shown that acceptable fish sauce could
be made using fish sterilized by irradiation.
The production process can take up to 18 months or more, during
which the fish autolyse, largely through the action of enzymes in the gut
and head of the uneviscerated fish, to produce a brown salty liquid rich in
amino acids, soluble peptides and nucleotides. Products in which auto-
lysis is less extensive are described as fish pastes.
346 Fermented and Microbial Foods