Biology Reference
In-Depth Information
In Africa salting and drying of fi sh for preservation is accompanied by
fermentation, but the period is short and the product is not transformed
into a paste or sauce. Although fermented fi sh products are a good source
of protein, they can be consumed only in limited quantities because of the
high salt content of these products. Fermentation of fi sh is especially used
in situations where drying of fi sh is not possible because the climate is too
wet and where cooling and sterilization of the product is too expensive.
In this chapter, three important traditionally fermented fi sh and fi sh
products for human consumption, i.e., fi sh sauce, fi sh paste and dried/
salted fi sh have been discussed with special emphasis on the microbiology,
biochemical compositions and food safety.
FERMENTATION
During fermentation of fi sh, protein is broken down to peptide and amino
acids in the presence of a high salt concentration. The fi sh protein is mainly
broken down by enzymes which come from the fi sh itself. These enzymes
are mainly present in the gut (Paludan-Muller et al., 2002). In traditional
fermentation methods where the intestines are removed from the fi sh,
fermentation will often be slower as there are fewer enzymes present in
the fl esh.
Role of Microorganisms
Microorganisms probably play no role in the breaking down of protein
during fermentation (Tanasupawat et al., 2006, 2007). However, micro-
organisms which can tolerate salt (because of the high concentrations of
salt which are used during fermentation of fi sh) do seem to contribute
to the specifi c taste and smell (described further on this chapter) of the
fermented product (Lopetcharat and Park, 2002; Sanni et al., 2002). In
some traditional fermentation techniques, such as in the production of
sushi
, a fermentable source of carbohydrates such as boiled rice is added
to the fermented fi sh product. This combination stimulates the growth of
lactic acid bacteria (LAB). The rice is a source of sugars for the LAB. Due
to the formation of lactic acid, which is desirable in these products, the pH
of the fi sh mixture is lowered making the product safer and easier to keep
(Gelman et al., 2001). In addition, spices such as garlic, pepper or ginger
are added to the safety of the products. Also, in some products garlic
may serve as a carbohydrate source for lactic acid fermentation (Paludan-
Muller et al., 1999).
