Biology Reference
In-Depth Information
Region: East Africa
Country:
Uganda
Product:
(a) Salted dried tilapia,
Alestes
spp., Nile perch,
Hydrocynus
spp.
(b) Sun-dried
Haplochromis
spp., sun-dried
Rastrineobola
spp. (dagaa)
Process:
(a) The fi sh may be gutted, split dorsally or headed and washed.
Smaller species may be processed whole or split at the belly to remove
the guts. The fi sh may be dried without salting, but when salt is used
only small quantities are sprinkled on the surface. It is left to stand for
three to six hours and then dried for three to seven days. Fermentation
occurs during salting and drying. The fi sh may be dried on rocks, mats,
the ground or, occasionally raised platforms.
(b)
Haplochromi
s spp. are usually dried by passing a stick through the
eyes of 10-12 individual fi sh. Ten such sticks of fi sh are joined to form a
mat which is then hung in the open air for the fi sh to dry. Rastineobola
spp. are spread on the ground or a mat to dry. The drying process takes
three to fi ve days. Fermentation occurs during drying.
Characteristics:
(a) The products may be very dry or semi-dry with a mild to moder-
ately strong smell. They are susceptible to insect infestation and mould
growth and require periodic drying to maintain quality. They can be
stored from one to three months.
(b) The fi nal products are greyish in colour, with a very hard and dry
texture. They have a very mild smell which becomes pronounced if
drying is inadequate. They are brittle and susceptible to insect infesta-
tion with a high incidence of fragmentation. Contamination with sand
is a major problem when the fi sh is dried on the ground.
Source:
Essuman, 1992.
MICROBIOLOGY AND BIOCHEMISTRY OF FERMENTED
FISH PRODUCTS
Microbiology
General Studies
Fish in its natural environment has its own microfl ora in the slime on its
body, in its gut and in its gills. These microorganisms (
Table 6.5
), as well
as the enzymes in the tissues of the fi sh, bring about putrefactive changes
in fi sh when it dies. Furthermore, the microorganisms generally present in
the salt used for salting also contribute to the degradative changes in the
fi sh. Microorganisms require water in an available form for growth and
metabolism. Halophiles grow optimally at high salt concentrations but
are unable to grow in salt-free media. Halotolerant organisms grow best
without signifi cant amounts of salt but can also grow in concentrations
higher than that of seawater. Xerophiles are those organisms which
grow rapidly under relatively dry conditions or below A
w
of 0.85, while
osmophiles can grow under high osmotic pressure. Most food-borne
bacterial pathogens are not able to grow in an A
w
range of 0.98-0.93
