10560723.ppt

Salting & Drying of fish

1. SALTING
AND
DRYING OF FISH

2. THEORY OF SALTING AND DRYING
THEORY OF SALTING
Salting is preservation of fish with
dry edible salt.
Salt absorbs much of water from
food and makes it difficult for
micro –organisms to survive.
Salt delays the activity of bacteria
or even inactivate them by
lowering the water activity.

3. THEORY OF DRYING AND
DEHYDRATION
DRYING
•Drying is one of the oldest
method of preservation of food.
•Drying refers to “Sun drying”
where fish is dries under open air
using solar energy to evaporate
water in the fish.
•The evaporated water is carried
out by natural currents

4. DEHYDRATION
Aprocessofdryingundercontrolled
operationalparameters like
temperature,airvelocityandrelative
humidityisknownasdehydration.
Itiscarriedoutinenclosed
atmospherewithfacilitiestocontrol
operationalparameters.

5. METHODS OF SALTING
DRY SALTING
Dressed fish is mixed with
crystalline salt in containers.
Salt and fish are spread in
alternate layers, the proportion
of salt increasing upwards.
Fish is allowed to remain in
brine for 2 –3 days and dried
afterwards
KENCH SALTING
A method of dry salting
except that the self –
brine formed is allowed
to drain off.
KENCH SALTING

6. BRINE SALTING
In this method of salting,
fish is kept immersed in
the in brine of desired
concentration for the
required time.
This a preliminary step to
smoking and canning
MIXED SALTING
An advantageous method over
brine salting for large and oily
fishes is mixed or “Pickle curing”.
Fish is mixed with dried salt and
packed in watertight containers
with salt sprinkled in each layer.
PICKLE CURING

7. METHODS OF DRYING
NATURAL DRYING
Solar and wind engines are made
use of in natural and drying
process.
High temperature (35-40 °C), low
Relative Humidity (< 70 –75%),
raised Platforms and drying racks
are required for natural drying
MECHANICAL DRYI NG
There are two types of mechanical
drying:
In one type, heat is transferred to
product through hot air/ gas usually
air.
In another type, heat is transferred to
the product through a solid surface.

8. MECHANICAL
DRYING
Cabinet
Drier
Kiln Drier
Tunnel
Drier
Drum
Drier
Vacuum
Shelf Drier
Spray
Drier
Drying through hot gas
Drying through a solid
surface

9. Cabinet Drier
Consist of insulated or non –
insulated framed structure with
trays where material is spread.
Fan is located inside to blow air
as ah heat source over the
material
Kiln Drier
It is a type of batch drier
with two -story building
The floor of upper story is
made up of slats on which
material is spread
The burners or furnace
producing hot gas is placed
on the lower floor.KILN DRIER

10. Tunnel Drier
Commonly used for drying
fish
These are made in form of
long tunnels, 10 –15 m long.
Trollysloaded with trays
containing fish are moved
into the tunnel
Hot air is blown over the
material across the trays
Spray drier
It is used for drying foods which are in
liquid or suspension form
Food in liquid is suspended in a stream
of hot air in a chamber where it gets
rapidly dried

11. Drum Drier
In drum drier heat is
transferred to the product
through solid surface. It is
used for drying fluid
materials.
Fluid is deposited over the
drum as thin film, and drum
is heated by steam, while it is
being rotated.
Vacuum Shelf Drier
It consists of vacuum tight
chamber with access door and
outlet for gases and vapours.
Vacuum will be drawn inside the
chamber through the vapour
outlet, and drying will be
proceeded under vacuum.

12. SPOILAGE IN SALTED FISH
“Pink or Red”
This occurs in salting during storage at warm weather
conditions where surface of fish becomes covered with
red slime.
It is caused by halophilicrods and coccioriginating from
salt .
They include Halobacteriumsalinaria, Sarcinamorrhuae,
S. littoralis, Micrococcus resens
Prevention: Storage of fish at low temperature
Moulds
Moulds grow at RH of 75 % or more.
“Dun” is a type of mould development in heavily
salted fish.
Give appearance as if sprinkled with ground
black pepper.
Preservation: low temperature storage and use of
good quality salt

13. SAPONIFICATON
Damage caused by aerobic microorganisms
active at low temperature.
It results in malodorous slime on the surface of
fish.
Prevention: Fish can be kept in brine containing
vinegar and water.
PUTREFACTIVE SPOILAGE
Slow salting process cause this
spoilage which cause flesh near
backbone to become tanned or
reddened with offensive odour.
Preservation: Any pre salting
operation that can accelerate the
salting

14. Infestation by maggots: Cheese flies (Drosophila casei)
are attracted to drying fish by bits smellandunhygienic
atmosphere
Rust:appearance of coloursimilar to rusting of iron on the
surface o fish is Rust
Generally occur in oily fishes like Sardine and Mackerel by the
oxidation of oil in fish due to atmospheric oxygen.
White spots: presence of Calcium and Magnesium in salt
cause whitening in flesh.
Fragmentation: Cured and dried fish becomes brittle and
break during storage and transportation.

15. SPOILAGE IN DRIED FISH
MOULDS:Moulds can grow on salted
or unsalted dried fish if the moisture
content is high and RH is above 75%. It
increases surface moisture owing to
other types of spoilage.
INSECT INFESTATION: Unsalted
dried fish are often infested with
Brownflies, ChrysomyaSpp., Lucilia
Spp., SarcophagaSpp. Etc.
Pesenceof salt can reduce the activity.
RANCIDITY:Fatty fish, are prone to
oxidation and development of rancid
flavour.
Airtight packaging can control
rancidity.

16. QUALITY STANDARDS FOR CURED FISH PRODUCTS AS RECOMMENDED BY
BUREAU OF INDIAN STANDARDS
Sl.
No.
PRODUCT MOISTURE(%) SODIUM
CHLORIDE (%)
BY MASS OF
MFB
ACID INSOLUBLE
ASH % BY MASS
ON MFB
(max.)
1.Dry-salted catfish(a) 35 25(min) 1.5
2.Dry-salted dhoma(b) 35 10-15 (min) 2
3.Dry-salted Horsemackerels
(Caranxspp.) (c)
40 25 (min) 1.5
4.Dry-salted Threadfin (Dara)
(d)
40 25 (min) 1.5
5.Dry-salted Leather –jackets
(Chorinemusspp.)
40 25 (min) 1.5
6.Dry-salted mackerel(e) 35 25 (min) 1.5
7.Dry-salted Jew fish (Ghol)
(d)
40 25 (min) 1.5
8.Dry-salted seer fish (f)45 30 (min) 1.5
9.Dry-salted shark (g) 40 25-30 (min) 1.5

17. Sl.
No.
PRODUCT MOISTURE(%) SODIUM
CHLORIDE (%)
BY MASS OF
MFB
ACID
INSOLUBLEASH
% BY MASS ON
MFB
(max.)
10.Dry–salted suirai(tuna) (h)35 25 (min) 1.5
Dried products
11.Dried and laminated
Bombay duck(i)
15 7.5 (max) 1.0
12.Fish maws (j) 8 - 1.5
13.Dried Prawn 20 5 (max) 1.0
14.Dried shark fins 10 - 1.5
15.Dried white baits
(Stolephorusspp.) (k)
20 2.5 (max) 7.0
Mfb= moisture free basis

18. Thank You