The paper deals with the investigations carried out on the preparation of odorless fish-starch flakes using partially deodorized trash fish meat and different sources of starch like corn, tapioca, maida and black gram. It has been found that the products using corn and tapioca are better compared to those prepared using other two starches, the product from corn being the best. The product has a protein content of about 20% and has been found to have a storage life of 4 months at 37°c

Govindan, T.K.

Venugopalan, V.

Aquatic Commons

UTILISATION OF TRASH FISH 
t PREPARATION Of fiSH FLAKE 
V. VENUGOPALAN AND T. K. GOVINDAN 
Central Institute of Fisheries Technology, Ernakulam. 
The paper deals with the investigations carried out on the 
preparation of odourless fish-starch flakes using partially deodourised 
trash fish meat and different sources of starch like corn, tapioca, 
maida and blackgram. 
It has been found that the products using corn and tapioca are 
better compared to those -prepared using other two starches, the 
product from corn being the best. The product has a protein content 
of about 20% and has been found to have a storage life of 4 months 
at 37°C. 
INTRODUCTION 
Trash fishes form a sizable fraction of 
our marine fish landings. In the year 1966, 
trash fishes like cat-fish (Trachysurus spp.), 
ribbon-fish (Trichurus spp.), leather jacket 
(Chorinemus spp.), sole (Cynoglossus 
spp.), silver bellis (Leiognathus spp.), 
sciaenids and other miscellaneous fish 
constituted 1,44,037 m. tons out of our 
total landings of 8, 89 651 m. tom (private 
communication). Some of the larger 
varieties of these are utilised by the curing 
industry, but the smaller and cheaper 
varieties are mainly utilized for the pro-
duction of fish meal intended for cattle 
and poultry feed. Attempts have also 
been made with some success for the 
production of fish protein concentrate 
which can be utilised for human consu-
mption as well. It may, however, be 
35 
pointed out that not much work has been 
reported as to how best the FPC can be 
incorp.)fated in the daily diet of human 
beings. So it was felt that a modified and 
ready compounded food material based 
on starch and fish which can be easily 
prepared for the table would go a long 
way in solving the protein deficiency of 
our population. 
Some work has been done in India 
on protein rich food materials based on 
starch and fish. Bhatia eta!., (1959) have 
reported the production of fish macaroni 
based on fish and wheat semolina or a 
mixture of these two with tapioca flour. 
Moorjani eta!., (i964) have reported about 
"Fricola", a fish enriched farinaceou:> 
prod'1Ct. Krishnaswamy et a!., (1965) 
have worked out a formula of a ready-to-
serve fish paste and fish- potato flakes. 
Assellberg1: and Chan (1962) and Assel-
lbergs (1962) have outlined the manufacture 
of fish potato flakes: 
The present work describes a method 
of production of fish flakes using cheap 
variety of trash fish (deodourised after 
cooking) and starch which can be consu-
med after simple frying in oil. The suit-
ability of starch from different sources was 
studied and comparison of the properties 
of flakes prepared out of different starches 
was made. 
MATERIA!;S AND METHODS 
Mixed trash fishes comprising mostly 
of cat-fish, Jew fish and Kilimeen obtain-
ed from Cochin were dressed and cooked 
in twice the weight of water for 30 minutes. 
After cooking, the meat was separated from 
the bones by handpicking. It was then 
deodourised by the method of Sen and Rao 
(1966). The meat was cooked in equal 
amout of water at pH 5.5 adjusted by the 
addition of ortho-phosphoric acid and 
pressed in canvas bag. The pressed meat 
was again dispersed in hot water at 
pH 5.5 and allowed to boil for a few 
minutes. Pressing out and boiling was· 
repeated once more and the meat deod-
ourised thus was pressed again and used 
for the preparation of fish flakes. 
The meat after deodourisation was 
homogenised with the following varieties 
of starch viz; corn, tapioca, and blackgram 
in the proportion, 
Deodourised fish meat 
Starch 
\Vater 
Salt 
lkg. 
1.25kg. 
2. 50-2.75kg. 
40g 
Homogenisation was done in a waring 
blender. It was then poured in flat alumi-
nium trays previously smeared with an 
edible oil (to prevent sticking) to a thick-
ness of lmm. The trays \Vere then ~assed 
36 
through a steam chamber on a belt con-
veyer at a speed of 1 m per minute. 
The cooking took 20 minutes and the cook-
ed film after cooling to room temperature 
was cut with a sharp knife to give flakes of 
of 2.5 X 2.5 em. size. 
The flakes were spread on trays and 
dried in a tunnel drier at a temperature of 
70°C. The drying time was found to be 
li hours at this temperature and 4! hours 
at 50°C. 
RESULTS AND DISCUSSION 
The degree of deodourisation of the 
meat at different stages was measured in 
terms of 9 5% alcohol extractive matter 
after drying to a moisture content of Ca 8%. 
The quantities of alcohol extractive matter 
were 14.17%, 8.92%, 3.15% and 1.87% after 
each succssive cooking and pressing. Even 
hough losses of lipid matter, soluble pro-
tein and non-protein substances during 
cooking and pressing might be the major 
cause of decrease in alcohol extractive 
matter, the odour bearing compounds be-
ing highly steam volatile are also eliminat-
ed along with the above compounds. The 
deodourised meat after drying had a moi-
sture content of 7.82%, total nitrogen: 
14.46%, non-protein nitrogen: 2.62%, 
wafer soluble nitrogn: 3.16% and free 
alpha-amino nitrogen: 0.31%. 
The drying rate of the flakes in the 
case of pr,;paration using corn starch is 
shown in fig. I. 
As might be expected, the drying rate 
curve was steeper at 70°C than at 50°C. 
Since the product was not affected in any 
way by drying at 70°C, this temperature 
can very well be applied for drYing since 
drying time was reduced to 39% of that 
at 50°C. 
The product using corn starch was an-
alysed after drying and the results are: 
40 
20 
10 
t=ig.l. D~VING RATE. 01= FISHPLAKE 
A- At a temp. of 50'b. 
e At a temp. of 70c 
0~~-.----~------~2~----~3~--~~4~-----:~ 
TiME ~N HOURS 
37 

10 
4 
2 
0 
fls-UI. B.E.T PLOT FOR 
A-Corn-Fish Flake 
8. Tapioca -Fish Flake 
lO 15 20 
pjpo(too) 
39 
TABLE I 
Starch used. dried flakes % increase in wt. %increase 
Maida 
Corn 
Tapioca 
Black-gram 
Tapioca Product 
Corn Product 
No.f5gm 
14 
14 
14 
24 
I 
II 
Gauge of polythene bag 
200 
300 
400 
during frying. volume 
8.5 79.2 
32.3 100.4 
28.0 91.0 
7.5 47.4 
Taste 
Overall qulity 
TABLE II 
Iutercept 
100/a1 c 
1.13 
1.00 
0.1919 
0.2917 
TABLE III 
Moisture content of 
flakes after 1 month 
storage at 92% RH 
10.80% 
12.45% 
12.25% 
m Colour on I u frying 
brown Poor F-P 
No colour change 
original pale Good Good 
yellow 
No colour change 
original pale Fair F-P 
brown 
charred Poor Poor appearance 
Optimum moisture on 
Dry Wt. Basis, a 1 
4.92% 
3.31% 
Moisture content of 
flakes after 1 month 
storage at 12% RH 
4.32% 
4.43% 
4.91% 
(Initial Moisture content 8.1 %) 
40 
Moisture: 7.40%. Protein ( N x 6.25): 
19.59%, Salt: 4.31%, Fat: 1.04% (DWB), 
Ash: 5.63% (DWB), Calcium (as Ca 0): 
450 mg% (DWB), Phoshorus. 323 mg% 
(DWB), Iron: 11.70 mg% (DWB) Starch: 
67.66% (by difference), calori:ffic value: 
408.0 (fried sample) 
Frying Characteristics 
The products prepared out of different 
starches were fried for 30-60 seconds in re-
fined ground nut oil at 250°C and the fry-
ing characteristics were measured in terms 
of intake of oil during fryina .. o/ increase 
b' /o 
in volume due to swelling, colour changes 
during frying and taste of the fried pro-
duct. The increase in volume (due to 
swelling) was measured on the principle 
based on which the cooking quality of rice 
was measured by Bienveindo 0. Juliano et 
a/., (1965). The dispalacement of kero-
sine by the same weight of flakes both be-
fore and after frying was measured and the 
difference reckoned as increase in volume. 
The results are given in table I. 
As seen from the figures in the table, 
the extent of swelling was least in the case 
of product from black-gram even though 
it had minim urn density as shown by the 
number per 5 g Maximum swelling 
was in the case of product from corn 
followed by the tapioca product. These 
significant differences in qualities in the 
products obtained using different starches 
can be attributed to the differing properties 
of the starch used. These results indicate 
that corn starch i<> the best for preparing 
the flakes as regards in:::rease in weight 
during frying and swelling properties as 
measured by increase in volume during 
frying. This was closely followed by 
tapioca starch, while the other two starches 
tried were less sa tis factory. 
It was found that after frying there 
was a loss of amino acids corresponding 
41 
to 11.57 mg N/1 00 g dry flakes, in the 
case of product using corn probably due 
to decomposition at the high temperature 
employed for frying. 
Equilibrium Relative Humidity studies: 
With a view to studying the storage 
characteristics of the product using corn 
and tapioca starches, equilibrium relative 
humidity studies were conducted as des-
cribed by Iyengar et a/., ( 196 5) and Strolle 
eta!., (1965). 
The fish flakes were powdered so as 
to pass through a 40 mesh size sieve and 
lots of 3-4 g were placed in petri dishes 
and exposed to different relative humidities 
obtained by placing different sa1t solutions 
of different % of sulphuric acid in dessi-
cators. The weight of each sa.mple was 
checked periodically until constant weights 
were attained. The equilibrium moisture 
contents were attained in all the cases 
within 4 days, and were determined by 
drying at 100-105°C for 6 hours. The 
values were plotted against the correspo-
nding relative humidities. (Fig. 2) 
As seen from the figure, the equili-
brium moisture contents show a steep rise 
beyond RH of 60%. Hence exposure of 
the product to an RH above 60% will 
cause rapid deterioration. The sample 
kepc in 92% RH became ammoniacal after 
4 days. Mold growth was noticeable in 
this sample after 6 days. No caking was 
found in any of the samples. 
Optimum moisture content: 
It is essential to limit ·the moisture 
content of the product to an optimum 
level in order to get the maximum sheif-Iife 
Knowledge of this optimum moisture 
level is necessary to prescribe the maxi~ 
mum aJJowable humidity Jin1its during 
packaging and storage. Salwin (1959) 
found that moi~ture content at which 
certain dehydrated foods have got maxL 
mum storage life agreed closely with the 
moisture content representing a calculated 
monolayer of adsorbed water. This 
monolayer was calculated in the case of 
fish flakes from moisture sorption data by 
means of Brunauer, Emmett and Teller 
(B. E. T. ) theory of multimolecubr 
adsorption. (Strolle and Cording Jr. 1965). 
The optimum moisture content was calcu-
lated by transferring the isotherm obtained 
from equilibrium relative humidity studies 
(in the range of 5-35% RH) by the B. E. T. 
equation. 
p 1 
+ 
where, 
c-1 
X 
p 
Po 
a =;:: g of water/1 00 g dry matter 
corresponding to a relative vapour 
pressure p/p 0 , p =moisture vapour 
pressure used in the experiment, Po = 
vapour pressure of pure water at the same 
temperature (28°C), c = a constant related 
to heat of absorption. 
. . p (100) 
The data were plotted w1th a~ 
a(po-P 
ordinate and _£__ (100) i.e., RH % as 
Po 
abscissa. A strainght line was obtained 
c-1 100 
with slope --and intercept -- (Fig. 3) 
a 1 c a 1 c 
From this graph, a 1 , i.e., the optimum 
moisture conent on dry weight basis (mo-
.nolayer of water adsorbed) was calculated. 
The values of slopes and intercepts in the 
case of the corn and tapioca products are 
given blow. (Table II) 
Bacteriological Examinations 
The product was tested for salmonell!a, 
streptococci and coliform, all of which 
were found to be absent. The total plate 
count was 9.0x 103 immediately after pre-
paration and 1.2 X 10 3 f g after 3 months 
storage at 37°C. This can be attributed to 
42 
the gradual destruction of the organisms 
due to the unfavourably low moisture 
levels in the product. 
Shelf-Life 
The fish flakes were found to remain 
in good condition for several months in 
sealed polythene bags as found by organa 
leptic studies. The variation in moisture 
content when the fish flakes are packed in 
different gauge polythene bags and stored 
for one month at different relative humid-
ities is shown in table III. 
The resu1ts indicate that polythene 
bags of various gauges tried are not suitable 
as a packaging material for this product in 
so far as they are permeable to misture 
vapour. Hence any commercial venture 
attempting to market this product should 
use moisture vapour proof packaging 
material. 
Not-withstanding the slight chang;e m-
colour, the product remained acceptable at 
the end of storage for 4 months at 37°C 
and had the same extent of swelling and 
crispness on frying as freshly prepared 
material. No rancidity was noticed pro-
bably because of low fat content. 
CONCLUSION 
Cooked and deodourised trash fish 
meat can be successfully utilised for the 
production of fish flahs containing 20% 
protein after mixing with carbohydrates. Of 
the various carbohydrates, corn and tapioca 
were superior to madia and black-gram, 
the product from corn being the best. 
ACKNOWLEDGEMENT 
The authors are grateful to Dr. A. N. 
Bose, Director and Dr. V. K. Pillai, 
Senior Research Officer of the Insti-
tute for their valuable guidance in the 
course of the work. They are also indebt-
ed to Sri K. Mahadeva Iyer, Resareh 
Officer, for the bacteriological analysis. 
REFERENCES 
A. 0. A. C., 1960. Methods of Analysis, 
Association of Official Agricultural 
Chemists, Washington. 
Asselbergs E.A.M., 1962. Proc. Potato Uti-
lization Cont., Baskersfield, California. 
(not seen in original) 
Asselbergs E. A.M., and Chan M. S. 1962. 
Food in Canada, 21-22. (not seen in 
original) 
Bienvenido 0. Juliano, Luiz U. Onate 
and Angelita M. Del Mundo. 1965. 
Food Techno/., 19, 6, 116. 
Bhatia D. 3., Moorjani M. N., Iyengar J.R., 
and Visweswaraiah K. 1959. Food 
Sci .. 8. 1. 
43 
Iyengar J. R., and, Sen D. P. 1965. J Fd. 
Sci. Tech., 2. 2, 55. 
Krishnaswamy M. A., Subha Rao K. R., 
and Lahiry. N. L. 1962. J. Sci, Ind. 
Res., 21, (D), 308. 
Moorjani M. N., Upadhye A. N., Lahiry 
N. L. Parpia H. A. B., Dumm M. E. 
and Pereira M. 1964. Symposium 
on the significance of Fundamental 
Reserch in the Utilisat:on of Fish, 
May 1964, (FAO) 
Salwin. 1959. Food Techno!. 13, 594. 
Sen D. P., and Satyanarayana Rao T. s. 
1965. J. Fd. Sci. & Tech. 3, 1. 
Strolle E. 0., and James Cording Jr., 1965, 
Food Techno!., 91, 5, 171. 


Utilisation of trash fish. Pt. 1. Preparation of fish flake

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Utilisation of trash fish. Pt. 1. Preparation of fish flake

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