Studies on mackerel (Rastrelliger kanagurta) of medium (4%) and high (11%) lipid contents quick frozen individually (IQF) and as blocks (BF) and stored at -23°C showed that block frozen mackerel had higher frozen storage shelf-life than individually quick frozen samples. IQF samples of medium and high lipid contents had shelf-lives of 17 and 20 weeks whereas BF samples of both series had 23 and 24 weeks respectively based on sensory evaluation

George, C.

Gopakumar, K.

Perigreen, P.A.

Ravindranathan Nair, P.

Thampuran, N.

Aquatic Commons

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P. RAVINDRANATHAN NAIR, CHINNAMMA GEORGE, NIRMALA THAMPURAN, 
P. A. PERIGREEN and K. GOPAKUMAR 
Central Institute of Fisheries Technology, Cochin - 682 029 
Studies on mackerel ( Rastrelliger kanagurta) of medium (4 %) and hio-h (11 %) 
lipid contents quick frozen individuaHy (IQF) and as blocks (BF) and stored ;t -23°C 
sh?wed that block frozen mackerel had higher frozen storage shelf-life than individu.aUy 
qmck frozen samples. IQF samples of medium and high lipid contents had shelf-lives 
of 17 and 20 weeks whereas BF samples of both series had 23 and 24 weeks respectively 
based on sensory evaluation. i 
Among the various species of marine food 
:fishes, mackerel constitutes 10 ~la of the total 
landings in India. This fatty fish is normally 
consumed in fresh condition. However 
during seasonal glut a substantial quantity 
is processed as salt cured fish. The high 
oil content in the fish stands in the way of 
preservation by freezing because of the deve-
lopment of rancidity during subsequent 
frozen storage. 
Freezing characteristics of fishes like oil 
sardine ( Sardinella longiceps) (Shenoy & 
Pillai, 1971; Chinnamma George et al., 
1985), spotted seer ( Scomberomorus guttatus) 
(Shenoy, 1976), pomfret ( Pampus argentius) 
(Kamasastri & Rao, 1967) are already 
reported. Lipid breakdown during frozen 
storage of oil sardine and mackerel was also 
studied (Viswanathan Nair et al., 1976; 
1978). This paper reports the results of the 
studi,es on the freezing and subsequent frozen 
storage characteristics of block frozen and 
individually quick frozen mackerel. 
Materials and Methods 
Fresh mackerel ( Rastrelliger kanagurta) 
procured from mechanised :fishing crafts 
operating off Cochin, was washed in potable 
water and divided into two lots. One lot 
was individuaUy quick frozen at -40°C, 
glazed by dipping in chilled wate:r and wrap-
ped in 100 gauge polythene film and stored 
in a master carton at -23°C. Other lot was 
Vol. 24, 1987 
frozen as 2 kg blocks in aluminium trays 
Hned inside with polythene film with suffi-
cient chilled water to form a glaze over the 
surface of the material and frozen at -40°C. 
The frozen blocks were then transferred to 
duplex cartons and stored at -23°C. 
Muscle with skin from 5-6 mackerels was 
taken and minced uniformly and this min-
ced musde was taken for chemical analysis. 
For bacteriological tests sample was taken 
in sterile dishes using sterile scissors. For 
organoleptic evaluation, the fishes were 
cleaned, cut to pieces and cooked in 2 % 
brine for 15 min and the quality was judged 
by a trained taste panel. 
The frozen stored material was drawn at 
intervals, thawed in running water and ana-
lysed as the fresh material. 
Moisture, lipids and non-protein nitrogen 
were determined according to the methods 
of AOAC (1975). Peroxide value (PV) was 
estimated by the method of Lea (1952) and 
free fatty acids by the method of AOCS 
(1946). Thiobarb]turic acid (TBA) value 
was determined as described by Tadadgis 
et al. (1960). 
The samples were analysed for total bact-
erial count, total colifonns, coagulase posi-
tive staphylococci and faecal streptococci. 
The procedure adopted was the same as 
that outlined in lndian Standards (IS: 
2237, 1971), except that for determination 
104 P. RAVINDRANATHAN NAIR, CHINNAMMA GEORGE, 
NIRMALA THAMPURAN, P. A. PERIGREEN AND K. GOPAKUMAR 
of total plate count incubation temperature 
of 29±2°C (room temperature) was used 
instead of 37°C. 
Results 
The changes in moisture of mackerel for 
both batches, (I) 4 % lipid and (U) 11 % 
lipid, stored at -23°C are presented in 
Table 1. The variation in moisture content 
observed between two batches can be accoun-
ted for the difference in lipid content. Signi-
ficant changes in moisture were not obser-
ved during frozen storage probably due to 
the effective protection of glaze and packing. 
Frozen 
storage 
weeks 
0 
4 
8 
12 
17 
23 
32 
Changes in moisture ( %) of indivi-
duv.,lly quick frozen (IQF) and 
block frozen (BF) mackerel with 
fat content 4 % (I) and 11 % (II) 
Batch I 
lQF BF 
72.0 72.9 
72.5 72.0 
73.0 72.2 
72.0 72.2 
72.5 72.0 
72.4 72.5 
72.9 72.5 
Frozen Batch II 
storage lQF BF 
weeks 
0 66.3 66.3 
5 67.0 66.9 
10 66.0 66.7 
15 66.5 66.8 
20 65.5 68.3 
24 66.0 67.l 
Table 2 represents the changes in non-
protein nitrogen. A definite pattern or 
trend is not seen in non-protein nitrogen 
during frozen storage. 
The total plate count of the :fish (Table 3) 
was of the order of 103 per g. For JQF and 
BF samples of both batches, the total plate 
count did not show any significant change. 
Pathogenic organisms like coliforms, stre-
ptococci or staphylococci were absent in 
frozen samples. The results showed that 
microbial changes were not significant in 
an the samples. 
Organoleptic changes during frozen 
storage are presented in Table 4. For both 
batches block frozen samples showed better 
acceptability and textural properties than 
IQF samples. The BF samples of both 
series had shelf-lives of 23 and 24 weeks 
Table 2. Changes in non-protein nitrogen 
of IQF and BF mackerel having 
fat contents 4 % (I) and 11 % (II) 
Non-protein nitrogen mg/lOOg 
Frozen Batch I Frozen Batch II 
storage lQF BF storage IQF BF 
weeks weeks 
0 694 694 0 657 657 
4 761 697 5 628 630 
8 762 764 10 669 684 
12 791 774 15 655 640 
17 613 586 20 722 583 
23 695 699 24 699 587 
32 626 657 
whereas the IQF samples had only 17 and 
20 weeks respectively 
Figs. 1 a and Ib show the changes in 
peroxide values for IQF and BF mackerel 
of batch I and II respectively during frozen 
storage. Both IQF and BF samples showed 
almost similar trend. But IQF samples 
invariably recorded higher values compared 
to BF samples. For batch I, the IQF and 
BF samples showed maximum increase 
50 o-----o I Q F 
o-----<> BF 
45 
0 
- 40 
~ 35 
I 
J 
I 
O 30 I 
0 I 
~ I l =~/ 
> 15f p 
t 101/ 
'!) 11' 
a.. I~ 
:t ' 
4 
A 
/ \ 
\ 
\ 
I 
\ 
\ 
\ 
\ 
\ 
' 
' 
\ ei... _______ _,, 
a ' ' i L__L_ 
8 12 15 20 24 28 32 
Period of storage in weeks 
Fig. la. Changes in PV of IQF and BF mackerel 
(Batch I) during frozen storage 
FISHERY TECHNOLOGY 
FROZEN STORAGE CHARACTER[STJCS OF MACKEREL 105 
Table 3. *Microbiological characteristics of IQF and BF mackerel kept at -23°C 
T. P. C. before freezing 1.143 x 104/g T. P. C. before freezing 8.29 x 104/g 
Batch I Batch II 
Period of Total plate count/g muscle Period of Total plate count/g muscle 
storage IQF BF storage IQF BF 
weeks weeks 
0 2.293 x 103 8.135 x 103 0 1.37 x 104 5.25 x 
4 9.767 x 103 1.89 x 104 4 4.50 x 104 4.10 x 104 
8 1.89 x 104 3.20 x 104 10 1.82 x 104 1.66 x ]04 
12 5.05 x 103 9.70 x 103 15 1.01 x 104 1.07 x 104 
17 3.05 x 103 9.194 X lQS 20 3.84 x 104 6.56 x 103 
23 3.08 x 103 3.31 x 103 24 7.51 x 103 1.15 x 104 
32 2.06 x 103 3.87 x 103 
*Coliforms, streptococci and staphylococci were absent in an the frozen samples of both 
the batches. However, the raw material of batch I recorded coliforms 10 and staphylococci 
70 and that of batch II streptococci 130. 
Table Changes in organoleptic che<racteristics of IQF and BF mackerel stored at -23°C 
Batch I Batch II 
Period of Period of 
storage IQF BF storage IQF BF 
weeks weeks 
0 ExceUent Excellent 0 Excellent Excellent 
4 Good Good 5 Good, Good 
slightly tough 
8 Good to fair, Good 10 Good, no Good, no 
slight tough rancidity rancidity 
texture 
12 Moderately Good to fair, 15 Fair to good Good 
tough texture, slight rancidity 
slight rancidity and toughness 
17 Fair, tough, Fair, slightly 20 Fair, modera- Good 
rancid tough, rancid tely tough, 
rancid 
23 Inedible, off Fair, tough 24 Inedible, high Fair, mild 
odour, rancid, rancid rancidity and rancidity and 
tough toughness toughness 
32 -Poor, highly Fair, rancid. 
rancid, very tough 
tough 
Vol. 24, 1987 
106 P. RAVINDRANATHAN NAIR, CHINNAMMA GEORGE, 
NIRMALA THAMPURAN, P.A. PERIGREEN AND K. GOPAKUMAR 
Period of ~orage in weeks 
Fig. lb. Changes in PV of IQF and BF mackerel 
(Batch II) during frozen storage 
4 8 12 16 20 24 28 32 
Period oif storage in weeks 
Fig. 2. Changes in FFA of IQF and BF mackerel 
(Batch I & U) during frozen storage 
upto 8 weeks storage and thereafter recorded 
a declining trend. 
The changes in TBA value showed a 
different pattern from that of PV as seen 
in Fig. 3a & 3b. TBA values of IQF sam-
ples showed rapid increase after 12 weeks-
of frozen storage in both samples. Organo-
leptic evaluation has shown that there is no 
rancid flavour upto 8 weeks of stornge. 
Low TBA values confirm this observation. 
But as storage life extends oxidation produ-
cts are formed resulting in the production 
of 2 thiobarbituric acid reactive carbonyls. 
24 -- IOF 
<>----..:. BF 
22 
20 
18 
O' 
g 14 
Q 
" O' 
s 12 
0 
> 10 
<( 
m 
r- 8 
6 
4 
; 1 Ar ___ ... ..e-----e..--- .... --o"'" 
2 / 
__ ...... ········· 
Peroo of s1oroqe 1n weeks 
... 
-"" 
Fig. 3a. Changes in TBA value of IQF and BF 
mackerel (Batch I) during frozen storage 
Olley and co-workers (Olley & Lovern, 
1960; Olley et al., 1962) noted that most of 
the free fatty acids in many species of fish 
originated from phospholipids. Viswanathan 
Nair et al. (1979) reported that in oil 
sardine ( Sardinella longiceps) production of 
FF A is higher in muscle (lipid content 6 %, 
compared to skin lipids (27 %) during frozen 
storage at -18° C. The present study 
indicates in mackerel the lipid hydrolysis is 
more when the fat content is less (Fig. 2). 
It can be concluded that production of FF A 
FISHERY TECHNOLOGY 
FROZEN STORAGE CHARACTERISTICS OF MACKEREL 107 
is higher in mackerel when it is lean and 
lower when the fish has maximum lipid. 
Fatty fishes were found to be less susce-
ptible to protein denaturation as a result of 
the protective effect of lipids during frozen 
storage (Dyer, 1951; 1953). When lipids 
were hydrolysed leading to the production 
of FF A, proteins were denatured at faster 
rate (Dyer & Fraer, 1959; Dyer & Dingle, 
1961). There are two possibilities (i) the 
FF A formed get absorbed on the surface 
of proteins giving a hydrophobic surface (2) 
the lipid hydrolysis results in loss of prote-
ctive effect of lipids on proteins. Conse-
quently fatty fishes can have an extended 
shelf-life in frozen storage compared to lean 
fish. This is found to be applicable to 
mackerel, which can be both lean and fatty 
at different seasons. However, this is not 
the case always and different species behave 
differently because of the difference in the 
type of FF A released and its inherent capa-
city to make myofibriUar protein insoluble 
(King et al., 1962). 
8 o---·-----o IOF 
e>----o BF 
., 
a. 
E 
0 
7 
6 
(/) 5 
CJ> 
0 
0 
2 
~ 4 
E 
ro 2 
I-
4 
.. o 
12 _ 16 20 24 
Period of storage in weeks 
Fig. 3b. Changes in TBA value of IQF and BF 
mackerel (Batch U) during frozen storage 
The present studies showed that mackerel 
can be preserved safely under frozen storage 
Vol. 24, 1987 
(-23°C) for a period of 23-24 weeks if quick 
frozen as blocks with sufficient glaze and 
packing. 
The authors express their gratitude to the Director, 
Central Institute of Fisheries Technology, Cochin 
for his kind permission to publish this paper. 
AOAC (1975) Official Methods of Ana-
lysis. Published by Association of 
Official Analytical Chemists, Washington 
D.C. 
AOCS (1946) Official and Tentative 
Methods, American Oil Chemists Society 
Chicago. 
Chinnamma George, P. K. Vijayan & 
P. A. Perigreen (1985) Harvest and 
Post-harvest Technology of Fish, Cochin 
Society of Fisheries Technologists (India) 
p.539. 
Dyer, W. J. (1951) Food Research. 522 
Dyer, W. J. (1953) Proceedings of Sym-
posiwn on Cured and Frozen Fish Tech-
nology. Sweed Inst. Food. Preser-
vation Research (Gieoteberg) Puhl. 
No.100,ChapterVU,p.12 
Dyer, vV. J. & Frazer, D. I. (1959) J. Fish . 
Res. Bd Canada.16, 43 
Dyer, W. J. & Dingle, J. R. (1961) in 
Fish as Food, Vol. 1, G. Borgstrom, 
(Ed.) Academic Press, NY. 
IS: 2237 (1971) Specification for Frozen 
Prawns (Shrimp), First Revision, Indian 
Standards Institution, New Delhi 
Kamasastri. P. V. & Ramananda Rao, D. 
(1967) - Fish. Technol. 78 
King, F. J., Anderson, M. L. & Steinberg, 
M. A. (1962) J. Food Sci. 27, 363 
Lea, C. H. (1952) J. Sci. Fd Agric. 3, 586 
Olley, J. & Lovern, J. A. (1960) J. Sci. 
Fd Agric. 644 
Olley, J., Pirie, R. & Watson, H. A. (1962) 
J. Sci. Fd Agric. 13, 501 
108 P. RAVINDRANATHAN NAIR, CHINNAMMA GEORGE, 
NIRMALA THAMPURAN, P. A. PERIGREEN AND K. GOPAKUMAR 
Shenoy, A. V. (1976) Fish Technol. 13, 
105 
Shenoy, A. V. & Pillai, V. K. (1971) Fish. 
Technol. 8, 37 
Tarladgis, B. G., Watts, B. M., Margaret, 
T. Y. & Duncan, L. (1960) J. Am. 
Oil Chem. Soc. 37, 44 
Viswanathan Nair, P. G., Gopakumar, K. & 
Rajendranathan Nair, M. (1976) Fish 
Technol. 13, 111 
Viswanathan Nair, P. G., Gopakumar, K., 
Antony, P. D. & Rajendranathan Nair, 
(1978) Fish. Technol. 15, 81 
V.iswanathan Nair, P. G., Antony, P. D. & 
Gopakumar, K. (1979) J. Fd. Sci. 
Tech.16, 151 
FISHERY TECHNOLOGY 


Studies on frozen characteristics of individually quick frozen and block frozen mackerel

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Studies on frozen characteristics of individually quick frozen and block frozen mackerel

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