V.Aiiuradha (1999) Feed Formulation for Fish and Poultry using Hideflesh from Tanneries

PROCESSING OF HIDEFLESH

2.1 INTRODUCTION

Most of the formulated diets for animals include fishmeal as an animal

protein source because of its high nutritive value and palatability. But the

availability of fishmeal has become scarce. Hence animal by-products and

wastes have been tried as alternate source of protein by several workers. Poultry

by-products meal (Steffens, 1994), blood meal (Lee and Bai, 1997 and Asgard and

Austreng, 1986) and fish silage (Jackson et ai, 1984) are some of the non-

conventional animal protein sources often incorporated in animal feed. However,

these products contain inherent materials like urea, nitrates, high percentage of fat

etc. Hence any non-conventional protein source should be subjected to treatments

before incorporating it in animal feed.

A number of methods have been practised to remove these inherent

materials and they include washing, pressure cooking, acid treatments, alkali

treatments, steaming etc. While processing the animal wastes, generally, two or

three methods are combined to help in the removal of the unwanted substances.

The feathers from the poultry industries, which contain a high percentage of

protein, are subjected to steam treatment and chemical treatment before

incorporation in the feed of fish and poultry (Baker et ai, 1981). Waste hairs from

the tannery are incorporated in the feed of fish after removing the keratin by

pressure cooking and acid treatment, thereby converting them into acceptable

protein (Moran and Summers, 1968 and Summers and Leeson, 1978). In the

present study an attempt has been made to use the wastes of tanneries i.e., limed

fleshings, after subjecting them to various processing, as animal protein source in

the feed offish and poultry.

Earlier works reveal that limed fleshingss from the tanneries have been

used as animal protein source in the feeds after washing, steaming and treatment

with organic solvents (Wisman and Engel, 1961; Cowey et al., 1979; Rao et al.,

1994 and Kandasamy and Raj, 1990). In the present study the method used by

Kandasamy and Raj (1991) has been modified for processing the fleshings from

the tanneries.

2.2 REVIEW OF LITERATURE

With the increasing demand for fishmeal, scientists all over the world are

looking for alternate sources of protein which are cost effective and easily

available. While using non-conventional sources, care should be taken to process

them and, their aminoacid profile should be analysed because the dependability

of protein depends on its aminoacid profile.

19

Strorn and Eggurn (1981) prepared fish visceral silage of cod (Gachis

mohiia) and saithe {Pollachius virens) by mincing the viscera and adding a

mixture of formic and propionic acids (1:1 w/v) to a concentration of 1.5 percent

and storing for four days at 30°C. The nutritional value of freshly prepared silage,

the silage stored for four days and the deoiled silage prepared after autolysis and

subsequent storage for 60 days at 15°C showed a protein content of 12.4, 13.3 and

13.9 percent, a fat content of 16.2. 0.1 and 0.2 percent and ash content of 1.3. 1.6

and 1.9 percent respectively. The feeding trial on rat showed the best performance

in deoiled silage stored for 60 days.

Hardy et al. (1984) prepared co-dried fish silage by adding 2 percent

sulphuric acid and 0.75 percent propionic acid (w/v) to a freshly ground whole

pacific whiting and stored in a container at a temperature of 12-15°C for 30 days.

The silage was periodically mixed and , after 30 days, the silage was neutralised

with lime to a pH of 6.2-6.5 and mixed with soybean meal (8.1%) and feather

meal (16.9%). The mixed silage was vacuum dried, ground and incorporated with

other ingredients (50%) in the diet of fish. An analysis of this diet showed 41.1

percent protein, 13.5 percent fat and 9.7 percent ash. The feeding experiment on

trout showed reduction in weight compared to the control, but the proximate

composition of the whole fish was not affected significantly.

Martins and Guzman (1994), used bovine blood cooked with rice meal as a

source of protein in the diet of Colossoma macropormtm (Cuvier). Fresh blood

was mixed with ground broken rice in the proportion of 5:1 and the mixing was

carried out in open steam jacketed kettle at a temperature of 75°C. The resulting

paste was pelleted and dried in forced air oven at 70°C. This meal was

incorporated in the diet of experimental fish replacing fishmeal at 50 percent level

for the duration of two months. The result showed a reduction in the final weight

gain but the proximate composition did not vary significantly from that of the

control fish.

Earthworm meal powder was prepared by Hilton (1983). Fresh worms

were collected and rinsed in water to remove the mud and then frozen at -20°C.

The freeze dried worms were powdered and used in the feed of trout replacing

fishmeal at various levels. The powdered meal showed 60.4 percent protein, 12

percent fat and 10.5 percent ash.

Cardenete et al (1991) incorporated earthworm meal after removing the

coelomic fluid and adding flavouring compound. This wormmeal was

incorporated in the diet of rainbow trout at the level of 50 percent of the dietary

protein. The experiment showed that the treated wormmeal was better accepted

than the non-treated wormmeal. However the feed consumption and protein

efficiency ratio,showed a reduction when compared to the control.

Dog fish offal was used in the diet of salmon after processing by Asgard

and Austreng (1986). The fish offal was freezed (-20°C) soon after collection and

preserved in a mixture of formic acid and anti-oxidant and then stored. This

processed silage was used in the diet of salmon as the source of protein.

Amphibian meal, another non-conventional source of protein, was

incorporated in the diet of Clarius gariepinus (Burchell) by Fagbendro et al.

(1993). Bull frogs, tadpoles and toads were collected and cooked separately for 30

minutes to coagulate the protein. The cooked meal was drained in a jute bag using

a twin screw press and fried in a kiln for 24h at 65°C. The dried materials were

powdered and used in the diet of experimental fish. The proximal composition of

the frog meal showed 65.28 percent protein, 16.76 percent fat and 17.07 percent

ash.

Niki et al. (1985) used protein recovered from effluent of fish meat in

producing surimi. During the production of surimi, while washing the fishmeat,

35 to 40 percent of edible meat was washed with water. This meat was

recovered by adding NaOH to the effluent and the protein was dissolved at a pH

of 10. The soluble protein was removed by centrifigation. The pH was adjusted to

5 by adding HC1 and heated to 80°C and the coagulated protein was separated. On

analysis, this meal showed 82.8 percent protein,and 2.8 percent fat. The feeding

experiment showed better performance in trout.

Nair and Prabu (1980) analysed the nutritional value of frog waste. Frog

wastes were collected from commercial frog processing industries and then

cooked at 0.7kg/sq.cm for 30 minutes, drained and dried in hot air oven at 90°C.

The chemical analysis of the meal showed the crude protein level of 67 percent.

Bhargava and O'Neil (1975) used poultry droppings of cage reared broilers

after the birds were marketed at 8 weeks of age. The droppings were spread and

dried by exposure to hot air (40°C). After removing the extragenous materials, the

dried excreta was powdered and used as a source of protein in the diet of poultry.

It contained 44 percent protein, 7 percent moisture, 2.9 percent fat and 9.98

percent ash.

22

Ahmed et al. (1996) processed layer excreta by heaping it for seven days

and then exposing it to the sun for two hours. Then the droppings were powdered

and incorporated in the diet of broilers. The proximal composition of the heaped

droppings was 22.64 percent protein, 3.89 percent fat and 34.1 percent ash.

Langer and Virk (1986), used the Plenrotus species (edible fungus) to

process poultry droppings. They observed that when droppings were used as

substrate, uric acid and crude fibre were reduced and the percentage of true protein

was increased, as Pleurotus mycelium used uric acid nitrogen for proliferation and

the fungal growth had no influence on the crude protein, ash and metabolizable

energy. The proximal composition of the treated droppings was 13.9 percent of

true protein and 21.8 percent ash. The high content of the ash reduced the

quantity of minerals used in the diet of poultry.

Harmon et al. ("1973) fed oxidation ditch mixed liquor as a nutrient solution

mixed with dry feed for pigs. Oxidation ditch is used in large farms for processing

all livestock wastes. The upper fraction of the residue that settled at the bottom

contains a microbial portion which is high in protein and aminoacid content. This

was used as a source of protein in the diet of pigs. Proximal analysis of residue

showed 25 to 50 percent crude protein, free aminoacids and high mineral contents.

The feeding experiment on pigs showed an increase of 2.5 percent in feed

consumption. Martin (1980), substituted this ditch liquor for tap-water for laying

hens. The results showed an increase in egg production.

Rao et al. (1994) used steam treated leather meal in the diet of broilers.

The leather shavings after initial washing, were steamed without pressure for an

hour in an autoclave, dried, powdered and then incorporated in the diet of broilers

at 10 percent level. In another treatment, the leather pieces were washed and

treated with lime solution at pH 9.7 for 24h, washed thoroughly, and then treated

with sulphuric acid at a pH of 2.3 for one hour. The sediment was separated,

washed, dried and powdered. This leather meal was incorporated in the diet of

broilers. The proximate analysis of the meal showed 76 percent protein.

In the present study limed fleshings from the tannery were used in the diet

offish and poultry after processing.

2.3 MATERIALS AND METHODS

COLLECTION

Around 2kg of wet hideflesh were collected from the Rathinam Tannery, a

nearby tannery (5km distance), soon after defleshing. The fleshings were packed

in polythene bags and transported by a vehicle immediately to the laboratory in

Gandhigram where they were processed without delay.

PROCESSING

TREATMENT I

Removal of salt and lime

Approximately two kilogram of the above fleshings were immediately

transferred to a plastic trough of 5/ capacity containing 2/ of tap water, and rinsed

thoroughly. Small pieces of (102.3 ± 2.6 g) fleshings were taken and soaked in

24

1, 2, 5, 10, and 15/ of water (one piece per soak water) for 3, 6, 12, 18 and 24h

with frequent stirring to remove the lime. Thus there were 25 troughs for each

series. After the due period the fleshings were removed, rinsed in distilled water

and dried in sunlight. Then they were kept in hot air oven at 80° C for 8h and

powdered. Five grams of the above powder was suspended in 20 ml of distilled

water and, after 5 minutes, the electrical conductivity was measured. Four

replicates were maintained. A graph was drawn to find out the optimum period of

soaking required in minimum quantities of water to remove the lime that can be

washed away.

TREATMENT II

Removal of calcium carbonate

In order to remove the insoluble carbonates that were not washed away by

the water, separate pieces of 99.8 ± 3.9g of fleshings were soaked in 1, 2, 5, 10

and 15/ of water for 3, 6, 12, 18 and 24h. After the due period of soaking the

fleshings were removed from the water and drained. Each set of washed fleshing

was suspended in 0. IN HC1 at a rate of lOOg of fleshings in 120ml of said acid (as

120ml was found to be optimum through cursory test). Thus there were five sets

for each time based washing (total 25 troughs). Then the fleshings were removed

from HC1 after 1.5, 3.0, 4.5 and 6.0h from the 25 troughs each individually. The

removed fleshings were washed in tap water, then in distilled water and dried as

it was done in treatment I.

The dried fleshings were powdered and 5g of this powder was suspended

in 20ml of distilled water, and, after 5 minutes, the electrical conductivity was

25

measured. A graph was drawn to find out the optimum period of soaking required

in 0. IN HCl for the removal of carbonates.

TREATMENT III

Removal of melting fat

Fresh fleshings were subjected to soaking at the rate of lOOg in 2.2/ of

water for 3h and then in 0.1N HCl for 1.5h as mentioned in treatment II and

washed in tap water. The water was checked with pH paper to confirm the

removal of acid. Then lOOg of fleshings (5 sets) was boiled with water (400ml)

for 15, 20, 25, 30 and 35 minutes to remove the melting fat. After the due period

of boiling, the emulsion was transferred to a separating funnel and the fat that

floated on the surface was collected in a pre-weighed petridish and dried in a hot

air oven at 60.C (overnight) and weighed. A graph was drawn to find out the

optimum time required for the removal of fat from the treated fleshings.

TREATMENT IV

Removal of residual fat

The fleshings which were subjected to soaking at the rate of lOOg in 2.2 /

of wash water for 3h, acid treated for 1.5h, boiled for 32.5 minutes as standardised

in treatments I, II and III, were dried in sunlight' and subsequently dried in a hot

air oven at 80°C for 8h and then powdered to get a coarse material. Of this

coarse material lOg was soaked in 120 ml of hexane and isopropanol mixture of

different ratios that is 1:1 (50 percent of hexane), 2:1 (67 percent of hexane), 3:1

(75 percent of hexane), 4:1 (80 percent of hexane), 3:2 (60 percent of hexane), 3:4

(43 percent of hexane) and 4:3 (57 percent of hexane) for an hour. The residual

fat that dissolved in the above solvent mixtures were separately filtered in a pre-

weighed petridishes, dried at room temperature and weighed. A graph was

developed to find out the suitable ratio of the solvents for the removal of the

residual fat.

In the selected solvent mixture , the flesh powder was treated for 60, 90.

120, 150, 180, and 210 minutes in order to standardize the duration of time

required for the removal of the residual fat. (However the data obtained on the

experiment depends on many other parameters)

The hideflesh powder prepared from the fleshings treated with the

standardised procedures of treatments I, II. Ill and IV was analysed for proximate

composition, following AOAC (1980) procedure. Moisture was determined by

oven drying at 105°C for 24 hours; protein (Nx6.25) by micro kjeldahl digestion

and distillation after acid digestion; lipid by extracting the residue with 40-60°C

petroleum ether for 8h in soxhlet; ash by ignition at 600°C in muffle furnace; and

carbohydrate by taking the sum of the values of crude protein, crude lipid, ash and

moisture and subtracting this from 100 (Maynard and Loosli, 1979). Energy

content was measured by Bomb calorimeter. The aminoacid profile was studied

by high pressure liquid chromatography.

2.4 RESULTS

The electrical conductivity of hideflesh powder prepared by subjecting the

fleshings to soaking in various quantities of water (1, 2. 5, 10 and 15/ of water) for

various time intervals (3, 6, 12, 18 and 24h) as indicated in treatment I is given in

figure.4. Soaking of limed fleshings for a longer time reduced the salt retentivity

of the fleshings. Three hours of soaking of lOOg of flesh in 1/ of water, also in

15/ of water gave an electrical conductivity of 1.79 and 1.26 mS/cm respectively.

In 24h of soaking the electrical conductivity in the same quantity of water was

read as 1.20 and 0.98 mS/cm. respectively. However, disintegration of the

fleshings was observed in the case of longer hours of soaking in larger quantities

of water and hence 3h of soaking in 2.2/ was taken as optimum time for soaking

the limed fleshings for the present study.

The electrical conductivity of hideflesh powder prepared from fleshings

subjected to 3, 6, 12, 18 and 24h of soaking in 1 , 2 , 5 , 10 and 15/ of water

and then treated with 0. IN HCI for 1.5, 3.0, 4.5 and 6.Oh as indicated in

Treatment II, is given figures 5 to 9.

28

figure 4 Electrical conductivity (rnS/cm) of hideflesh powder prepared from the fleshings (102.3±2.6g) soaked in various quantities of water

(1, 2, 5, 10 & 151) for different time intervals (3, 6, 12, 18 & 24h)

2.0

4 8 12

Quantity of water (/) 16

3h-y =

6h-y =

12h-y =

18h-y =

24h-y =

1.753425

1.606822

1.473760

1.300830

1.175014

- 0.03567x

- 0.03376x

- 0.2784x

- 0.02103x

- 0.0137x

Figure 5 Electrical conductivity (mS/cm) of hideflesh powder prepared from fleshings

(102.3±2.6g)soaked for 3h in various quantities of soak water and then treated with .IN HCI for

different time intervals (1.5, 3.O., 4.5 & 6h)

• 1.5h-y = 9 3h-y -+ 4.5h-y = t 6h-y =

1.546137 1.421836 1.331807 1.223892

- 0.02062x - 0.01755x - 0.01997x - 0.01695x

4 8 12

Quantity of water (/) 16

Figure 6 Electrical conductivity (mS/cm) of hideflesh powder prepared from fleshings

(102.3±2.6g)soaked for 6h in various quantities of soak water and then treated with .IN HCI for

different time intervals (1.5, 3.0., 4.5 & 6h)

1.6 r

4 8 12

Quantity of water (f) 31

* 1.5h-y = 1.484314 *3h-y = 1.370597 f4.5h-y= .1.269664 *6h-y = 1.181384

- 0.02186x - 0.02039x

- 0.01782.x - 0.01505x

figure 7 Llectncal c o n d u c t i v i t y (mS/cm) of hideflesh powder prepared from fleshings

(102.3±2.6g) soaked fo r I 2 h in various quantities of soak water and then treated with 0. IN HCI

for different time i n t e r v a l s (1.5, 3.O., 4.5 & 6h)

figure 8 Electrical c o n d u c t i v i t y (mS/cm) of hideflesh powder prepared from fleshings

(102.3±2.6g) soaked fo r 1 8 h in various quantities of soak water and then treated with 0.1N HCI

for different time i n t e r v a l s (1.5, 3.O., 4.5 & 6h)

Figure 9 Electrical conductivity (mS/cm) of hideflesh powder prepared from fleshings

(102.3±2.6g) soaked for 24h in various quantities of soak water and then treated with O.lN HCl

different time intervals (1.5, 3.0., 4.5 & 6h)

Figures 5 to 9 show a reduction in electrical conductivity with increased

hours of treatment in 0.1N HC1. The electrical conductivity at different hours of

soaking in water followed by treatment in 0.1N HC1 is calculated from figures 5

to 9 and given in Table 8. From the table it is easy to locate quantity and hours of

soaking in water and hours of treatment in 0.1N HC1 for a required electrical

conductivity.

For example, an electrical conductivity of 1.3 mS/cm could be arrived at by

soaking lOOg fleshings in 13.8/ of water for 3h followed by 1.5h of treatment in

0. IN HC1. The same electrical conductivity could also be arrived at by soaking

fleshings in 9.21 of water for 3h followed by 3h treatment in 0. IN HC1. Depending

upon the availability of water and the time, for the required electrical conductivity

the required quantity of water could be selected from the table.

In the present study 1.5mS/cm was taken as the required electrical

conductivity as many fish feeds show an optimum electrical conductivity of

1.5mS/cm. To get this electrical conductivity the fleshings were soaked in 2.2/ of

water for 3h followed by 1.5h treatment in 0. IN HC1.

34

Table 10 Quantities of water required, hours of soaking in water and in 0.1N HCl for the required electrical conductivity (Quantity of flesh 102.3±2.6g).

Though an electrical conductivity of 1.5mS/cm was also observed by soaking

fleshings in 8 and 5.5 / o f water for 3 and 6 hours respectively (figure.4),the

carbonates in the fleshings were not removed as they are insoluble in water and

required a weak acid (0. IN Hcl) to eliminate them.

The percentage quantity of melting fat recovered from the fleshings

(102.3±2.6g) subjected to soaking in 2.2/ of water for 3h and then treated with

120 ml of 0. IN HC1 for 1.5h and washed thoroughly to remove the acid and then

boiled with water for 15, 20, 25, 30 and 35 minutes (Treatment III) is given in

figure. 10 The graph shows a positive correlation between the boiling time and

percentage of fat recovered. As observed in figure. 10, the fat melted only upto an

optimum time of 32.5 minutes and the quantity of fat recovered was 6.7 percent.

Further increase of boiling time did not promote the release of melting fat and

hence 30 minutes was taken as the optimum time required for melting the fat from

the fleshings.

Figure 10 Percentage of melting fat recovered from treated fleshings at different

time intervals

Besides the melting fat recovered by boiling, the fleshings also contain

other residual fats that are removable only by organic solvents. In the present

study hexane and isopropanol mixture was used to dissolve this residual fat. The

percentages of residual fat recovered from the fleshings subjected to treatment in

hexane and isopropanol solvent mixture of various combinations i.e., 50 percent

hexane(l: 1), 66.7 percent of hexane (2:1), 75 percent of hexane(3:1), 80 percent of

hexane (4:1), 60 percent of hexane (3:2), 57 percent of hexane(3:4) and 43 percent

of hexane(4:3) are shown in figures 11 and 12. As it is observed, with increase

in the percentage of hexane, the percentage of fat recovered from the hideflesh

powder also increased showing a positive correlation.

Figure 11 Percentage of residual fat recovered from treated fleshings in fixed

percentages of isopropanol and change in percentage of hexane solvent mixture

(1:1, 1:2, l:3 and 1:4)

Figure 12 Percentage of residual fat recovered from treated fleshings in different

combinations of hexane and isopropanol (both hexane and isoproponal share

changing)

The recovery of fat was 4.19 percent in 80 percent of hexane (4:1) and 4.20

percent in 75 percent of hexane (3:1). The results indicate that the hexane soluble

fats i.e., hydrocarbon chains of fatty acids are more in the fleshings.

Figure 12 shows that the percentage of fat recovered was higher in a

mixture of hexane and isopropanol at a combination of 60 and 40 percent (3:2)

38

than in other combinations. Hence 60:40 percent of hexane and isopropanol was

taken as optimum dosage to dissolve the residual fat.

The time required for the treatment of hideflesh powder in the solvent

mixture of hexane and isopropanol (3:2) to remove maximum quantity of fat is

shown in figure 13. It has been observed that, at 60 minutes, the percentage

removal of fat was low (5.22 percent) and at both 180 and 210 minutes the

removal of fat was high (5.76 percent) and, that, further increase of time did not

improve the rate of recovery of fat. However this depends on other parameters

like the size of the particles.

The graph shows that the optimum time of treatment required is 200

minutes and hence that was taken as the optimum time required for treatment of

the flesh powder in 3:2 hexane and isopropanol solvent mixture for the removal of

redisual fat.

39

The proximate composition of hideflesh powder prepared from fleshings

(102.3±2.6mg) soaked in 2.2/ water for 3h followed by treatment with 120 ml of

0.1N HC1 for 1.5h and then washed and boiled for 32.2 minutes to eliminate the

melting fat, treated with hexane and isopropanol solvent mixture (3:2) for 200

minutes, dried at room temperature, powdered, sieved through 420 micron sieve is

given in figure. 14. The figure shows that the percentage of protein is high (80.02

percent) in the processed hide flesh powder and the energy value is 4230.6 cal/g.

Figure 13 The time required for the recovery of residual fat from 3:2

combinations of hexane and isopropanol

Figure 14 Proximate composition of processed hideflesh powder

Protein 80.2%

Carbohydrate 5.4%

The aminoacid profile of the processed hideflesh powder is given in Table

9. The hideflesh powder contained both essential and non-essential aminoacids.

However the percentage of sulphur aminoacids are comparatively less.

41

2.5 DISCUSSION

There is a possibility of recovering a considerable quantum of animal

protein from hidefleshings (solid waste) which are otherwise wasted in the

tanneries while processing animal skins for preparing leather. Usually it is

abandoned in the backyard to decompose or used as fertilizer or as raw material

by the gelatin industry. However, proper utilisation of the fleshings could lead to

42

the production of large quantities of useful animal protein for animal feed. In the

present study, an attempt has been made to recover edible protein from the

fleshings and to use it as an animal protein source in the place of fishmeal in the

diet of fish and poultry.

Generally the hides/skins which are skinned in the slaughter houses are

immediately preserved in common salt. In the tanneries the salted hides/skins are

subjected to treatment with lime for 15 or more days to loosen the hairs. After

removing the hairs the hides/skins are defleshed. Hence the fleshsings have to be

subjected to deliming process before recovering the protein.

When non-conventional protein sources are used as ingredients in the feed

of reared animals they have to be processed to remove the undesirable factors

present in them and also to improve the quality of the protein. Methods followed

by scientists for the removal of undesirable factors depend upon the nature of the

raw material to be processed. When hair meal was prepared for poultry (Moran

and Summers, 1968) the hair was washed and cooked with and without pressure

and then treated with acid in order to change the undigestible keratin into

digestible form, before incorporation in the feed. In the present study the hideflesh

were subjected to washing with water followed by acid treatment to eliminate the

unwanted and undesirable substances and then boiled followed by solvent

treatment to improve the quality of protein so that the rate of protein-conversion

could be improved in the experimental organisms'.

In order to standardize the procedure for the deliming process, the

quantity of water needed and also the time required for deliming were

43

standardized by soaking the fleshings in various quantities of water (1, 2, 5, 10

and 151) for various time intervals (3, 6, 12 18 and 24h) and the electrical

conductivity (a measure of salt content) of hideflesh powder was read to find out

whether the deliming process was complete. The results showed that there is a

decrease in the electrical conductivity in the treated hideflesh powder which

indicates that soaking in water reduces the salt retentivity of the fleshings.

Using water to dissolve salts is a common practice, for water is a good

solvent, and also it is inexpensive when compared to many chemical treatments.

Wisman and Engel (1961), Waldroup et air (1970), Cowey el al, (1979),

Kandasamy and Raj (1990) and Rao el al. (1994) while processing hideflesh.

used ranning water to remove the salt initially. When large quantities of limed

fleshings are to be processed, it requires huge quantities of fresh water and hence,

in order to minimize the usage of water, the fleshings were soaked in water and

frequently stirred.

The results showed that in 3h soaking (102.3+2.6g) in 2.2/ of water helps

in the removal of considerable quantity of salts from the fleshings. However,

longer hours of soaking in the same quantity of water did not show marked change

in the electrical conductivity which indicates that optimum level has already been

reached.

Besides soluble salts, the fleshings also contain salts like calcium cabonates

and sulphides which are insoluble in water but soluble in weak acids. Hence the

fleshings were treated with 0.IN HC1 which react with carbonates and change

them into soluble chlorides. Treatment of fleshings in 0.1N Hcl for 1.5h caused

44

loss of some percentage of minerals, but it did not affect the nutritional quality of —

the fleshings. Kadirvel and Thanu (1985), while preparing hairmeal for the

poultry, subjected the water-washed hair to alkali (NaOH) treatment at the pH of

10.5, neutralized it with 1 N HC1 (to a pH of 7.5) and then incorporated it in the

feed and found that this treatment does not produce any leg weakness in the

chicks.

For deliming the hideflesh Rao et al. (1994), used ammonium chloride and

Wisman and Engel (1961) used hydrochloric acid and phosphoric acid.

Removal of lipids increases the percentage availability of protein. The

percentage of fat present in the fleshings depends upon many factors like age of

the animal, sex, health condition etc. In the present study the fleshings were

collected only from hides and not from skins.

The fleshings contain high percentage of fat, which has to be reduced to an

acceptable level. High fat content in the feed is generally not preferred by both

fish and poultry. Such feeds increase the abdominal fats (Summers et al., 1992).

Steaming is the method followed by many scientists to reduce the fat

content. As boiling with water for a short period does not alter the protein quality

but changes the undigestible protein into digestible form besides removing the fat.

in the present study the fleshings were boiled with water for 30 minutes.

45

Hossain (1988), when used scarp fish as a source of fishmeal in the feed

for the fish culture, steamed the scarp fish for 40 minutes and pressed it by presser

to remove the oil and water as much as possible. Kandasamy and Raj (1990) also

used boiling method to reduce the fat content in the fleshings. In the present study

also the same method was followed.

Besides steaming, heating was also practised to remove fat. Wisman and

Engel (1961) used drum drying method to reduce the fat content in the fleshings.

Fish silage was heated to 30°C to facilitate the removal of fat (Johnson and

Skrede, 1981 and Strom and Eggum, 1981). Thermal and hydrothermal heating

were used by Abel et al. (1984) in soybeans to improve the oil extractability of

soybean.

Besides the melting fat the fleshings also contain other residual fats which

can be removed only by solvent treatment. Using organic solvent to extract the fat

from oil cakes is commercially practised. The lipids in the fleshings have both

hydrocarbon chains of fatty acids and carboxyl group. Generally the hydrocarbon

chains of fatty acids are recovered by hexane and isopropanol which is a high

polar lipids. Raldin (1981) recommended hexane and isopropanol to extract lipids

from the animal tissues. In order to recover the polar and non-polar lipids from

the hideflesh, in the present study, hexane and isopropanol mixture was used and it

was observed that 3:2 ratio of hexane and isopropanol mixture was most suitable

for the removl of fat and the time required was 200 minutes.

Use of organic solvents to extract the fat was practised by many scientists.

Rao et al. (1994) used acetone to recover the fat from the fleshings. Kandasamy

46

and Raj (1990) used hexane and isopropanol in the ratio 3:2 to recover the fat.

Chloroform was used to remove the fat from the fleshings by Cowey et al. (1979).

Hossain (1988) used petroleum ether to defatten the scrap fish meal and later the

solvent was removed by drying. Folch et al. (1957) used chloroform and

methanol to recover the fat. Asgard and Austreng (1985), while processing dog

fish offal as a feed for salmonids, used trichlorethylene to extract fat after careful

mixing with sodium sulphate.

Carpenter et al. (1952) reported destruction of riboflavin and pantothenic

acid in acid or alkali treated meal. Kadirvel and Thanu (1985) also reported a

reduction in the absorption of vitamins and minerals in the intestine when alkali

treated hairmeal which was neutralized with acid was fed to broilers. However, in

the present study, while formulating the feed, minerals and vitamins were added in

sufficient quantity. No deficiency diseases were observed in the experimental

animals.

The proximate composition of the processed hideflesh powder is shown in

figure 14. The crude protein content of the hideflesh powder was 80.02 ±2.17

percent. Wisman and Engel (1961) observed 68.3 percent of protein in dram dried

fleshings and 67.8 percent of protein in acetone treated fleshings. Cowey et al.

(1979) observed 55 percent of protein in the hideflesh. This variation in protein

content may be due to the processing technology followed or it may be due to

variation in the age and health condition of the slaughtered animal and also due to

other practices involved in the processing of raw hides/skins like the condition in

which the hides were transported, the quantity and strength of the calcium used

and the number of days taken for liming etc.

47

The aminoacid profile of the hideflesh powder is given in Table 11. It

shows that the hideflesh powder contains a high percentage of histidine (10.61)

and a low percentage of methionine (0.41). Besides the ten essential aminoacids

the fleshings also contain a few non-essential aminoacids like glutamate, serine

aspartate etc. Except for the sulphur containing aminoacids the quantity of the

rest of the essential aminoacids are not much different from that of the fishmeal.

Wisman and Engel (1961), Cowey et al. (1979) and Kandasamy and Raj (1990)

also observed a lesser percentage of sulphur containing aminoacids in the

hideflesh powder.

Deficiency of certain aminoacids in the non-conventional protein sources is

not an uncommon feature. In feathermeal Baker et al. (1981) observed 86.8

percent of crude protein but when it was analysed for aminoacids, the profile

showed 0.45 percent methionine, 0.45 percent lysine and 6.36 percent total

sulphur containing aminoacids. Haemoglobin powder (Lee and Bai, 1997) when

analysed for aminoacids showed 6.3 percent histidine and 1.7 percent methionine.

The processed pig hair, another non-conventional source of protein (Summers and

Leeson, 1978) contained 80 percent crude protein and its aminoacid profile

showed 0.77 percent histidine and 0.48 percent tryptophan. Meat and bone meal

used in the diet of fish (Kikuchi et al., 1997) showed 52 percent of protein and the

aminoacid content showed deficient in methionine and lysine. It all reveals that

high percentage of protein does not guarantee the presence of all essential

aminoacids and in right quantity and however the deficiency can always be

overcome by incorporating certain ingredients which are rich in such aminoacids

and thus making the compounded feed a whole meal for the cultured organisms.

48

Hence in the present study the hideflesh powder which was prepared by

subjecting the fleshings to the standardized procedure was incorporated as an

animal protein source in the place of fishmeal along with otlier ingredients of

animal and vegetable origin and prepared in the form of compounded feed for fish

culture and poultry farming.

49

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