Liquid nitrogen frozen products are biochemically and organoleptically superior to conventional plate frozen products but beneficial effect of liquid nitrogen freezing over conventional plate freezing can exist only up to 59 days at a commercial storage temperature of -18°C

Chakrabarti, R.

Chaudhury, D.R.

Aquatic Commons

Advantages u itrogen Freezi g of 
Penaeus monodon Over Conven al ate Freezing 
R. CHAKRABARTJ 
Kakinada Research Centre of Central Institute of Fisheries Technology, Kakinada - 533 003 
and 
D. R.CHAUDHURY 
Department of Food Technology & Biochemical Engineering, Jadavpur University, 
Calcutta - 700 032 
Liquid nitrogen frozen products are biochemicaUy and organoleptically superior 
to conventional plate frozen pro.ducts; but beneficial effect of liquid nitrogen freezing 
over conventional plate freezing can exist only upto 59 days at a commercial storage 
temperature of -l 8°C. 
Freezing is one of the commercial methods 
for preservation of food, p:i.rticularly prawn, 
which is very susceptable to spoilage. Pro-
cessing of prawn :is one of the established 
indnstries in India and the amount of foreign 
exchange earning through it has already 
exceeded Rs. 300 crores (MPEDA, 1983). 
Liquid nitrogen frozen pawn has several 
advantages over conventional plate frozen 
prawn. The main advantage of the liquid 
nitrogen freezing is that the additional 6-15 % 
of meat, which is at present used in conven-
tional plate freezing to compensate the loss 
during freezing and thawing will not be 
reqired. This will save about 10 % of our 
foreign exchange (Rs. 31 crores) and in 
addition quality is much superior to the 
conventionally frozen products. Effort 
has therefore been made in this communi-
c~tion to judge the quality of the liquid 
mtrogen frozen product through biochemical 
indices and to study storage life of liqPid 
nitrogen frozen prawn under commercial 
storage condition in our country (-l8°C). 
Mate.rials and Methods 
Freshly cau.ght Penaeus monodon (30 to 
40 whole prawn per kg) was brought to the 
laboratory under ice. Dressed prawns were 
washed, wrapped in polythene film and 
sv.bseque1:tly frozen in contact plate freezer 
(-40°C). Another lot, packed in mylar 
pouches, was frozen by spraying type liquid 
nitrogen freezer. The average cooling rate 
in the latter was 5°C/m:in from + 1°C to 
-40°C and it was 10°C/min upto -60°C. 
Both the plate frozen and liquid nitrogen 
frozen products were stored at -l8°C 
in a freezing factory situated nearby. 
Organoleptic analysis of thawed samples 
was carried out and the result was scored 
as overall quality on a nine point hedonic 
scale (Little, 1958; Hill & Giew, 1973) using 
a score of 5 as the limit of acceptability. Drip 
loss was measured as percentage of loss of 
weight of initial weight on thav;ing. 
Salt soluble protein was extracted by the 
method of Ironside & Love (1958) and the 
protein content was measured by Fo.lin & 
Lawry method. Total volatile base nitrogen 
and trimethyl amino nitrogen were measured 
by Conway microdiffusion method (1947). 
Alpha amino nitrogen was measured by the 
method of Block & Balling (1951). Adeno-
sine monophosphate (AMP) and inosine 
monophospha'te (IMP) content in thawed 
muscle were measured by the method of 
Spinelli & Kemp (1956). 
Results and Discussion 
Table 1 shows that drip loss of liquid 
nitrogen frozen sample is considerably less 
FISHERY TECHNOLOGY 
ADVANTAGES OF LIQUID NITROGEN FREEZING 45 
Table 1. Changes during freezing of prawn 
Sample Organo- % drip loss Moisture Salt soluble AMP 
leptic by weight content protein µ mole/g 
score 
Plate freezing: 
Before freezing 9 
After freezing 8 
Liquid nitrogen freezing: 
Before freezing 9 
After freezing 8.5 
than that of plate frozen. Electron micro-
graph plates (Love, 1968) of slow frozen 
cod muscle shows that the ice can be seen 
as large round columns for more extensive 
than extracellular spaces with several layers 
of compressed and dehydrated cells. Ele-
ctron micrograph (Love, 1968) of the cross 
section of the outer margin of a single frog 
muscle cell which had been plunged into 
isop~ntane (-150°C) shows myofifaments 
are regularly s.p3.ced as in unfrozen muscle 
and there is no evidence of displacement 
by ice. Modification to either the protein 
surface or to the interaction between 
protein molecules during freezing can result 
changes in water holding capacity of gel 
network of actin and myosin in muscle, thus 
drip will also result on thawing(Connell,1968) 
Table l also shows that salt solv.ble protein 
of liquid nitrogen frozen prod11ct is more 
than that of plate frozen product. This 
shows more of denaturation of protein 
dm-ing plate freezing. The reduction in 
total extractable protein (salt soluble pro-
tein) was du.e to the increase in insolubility 
of 'myosin because of chemical changes, 
physical changes and salting out in hyper-
tonic solution ( > 5 % NaCl) formed by the 
p:irtial freezing .. that is, below eutectic point 
-55 to -65°C of tissue W.?"ter. Love et al. 
(1958) observed that the freezing at various 
temperature e.g. -78°C, -60°C etc. and 
immediate thawing reduced s1lt soluabie 
nitrogen content from 96 % to about 87 %-
4.5 
2.8 
Ta.ble 1 also shows that the retention of 
moistl':re and AMP in liquid nitrogen frozen 
p;:-oduct was. more than that in plate frozen 
product. This. confirms that the damage 
to prawn muscle in liquid nitrogen freezing 
Vol. 24, 1987 
% % 
80.2 12.1 0.84 
77.5 10.5 0.45 
80.2 12.1 0.84 
80.l 11.7 0.63 
is comparatively lesser than that to plate 
frozen product. 
Bo.th the liquid nitrogen frozen 
product and plate frozen product 
were stored at-l8°C. Fig. l shows that the 
drip loss increases and salt soluble protein 
content (in thawed muscle) decreases during 
frozen storage. Both the parameters of 
liquid nitrogen fmzen pro.duct touch the 
respective value of plate frozen sample 
(immediately thawed after freezing) in 59 
d1ys. It is further evident from Fig. 2 that 
the rate of decrease in AMP and moisture 
content (in thawed muscle) of liquid nitrogen 
frozen meat was noticed during frozen 
storage, but both the values were more than 
12 
* 
5 
c 4.5 
·- !0-5 
-~ 10 ~ 4 " 0 
'- // .5 Q. 
"' IP /. <J) 
.0 3 2. . 
.2 
.Q. 0 
'-
"' 0 
:!::: 6 0 2 (/) 
4 59) 0·25 
0 20 40 60 90 
Storage ln days 
- - - - Plate frozen (thawed immediately after 
freezing) 
-·-·Drip loss of liquid nitrogen frozen 
--· Salt soluble protein in liquid nitrogen frozen 
Fig. 1. Changes in drip loss and salt soluble protein 
on frozen storage 
46 R. CHAKRABARTI AND D. R. CHAUDHURY 
Table 2. Changes in liquid nitrogen frozen product (in thawed muscle) during storage 
TMAN mg% 
TVBN mg% 
Alpha amino 
nitrogen mg% 
IMP µ mole/ml of elute 
Organoleptic overaU quality 
Fresh sample 
5.15 
13.86 
263.4 
0.82 
9 
the respective values of plate frozen prawn 
(thawed immediately after freezing) during 
120 days of frozen storage storage. Thus 
Figs. l and 2 indicate that the quality of 
liquid nitrogen frozen prawn even after 
storage at -l8°C for 59 days was comparable 
to the quality ot plate frozen sample thawed 
immediately after freezing. Increase in drip 
loss in liquid nitrogen frozen product du.ring 
storage is due to (1) imigratory recrystallisa-
tion resulting in formation of big crystals (2) 
desiccation causing damaging effect on 
myosin due to removal of critically located 
water molecules (3) salt denaturation of 
muscle protein. 
StO<"age in days 
- - - - Plate frozen (thawed immediately after 
freezing) 
- . - . AMP content in LN frozen (in thawed muscle) 
--- Moisture content in LN frozen (in thawed 
muscle) 
Fig. 2. Changes in AMP and moisture content on 
frozen storage 
Table 2 shows that except alpha amino 
nitrogen content other parameters are almost 
constmt during frozen storage. The decrease 
in alpha amino nitrogen content is probably 
due to increase in drip loss. The retarded 
growth of cold resistant microbes and decre-
asing trend of proteolytic enzymatic activity 
with lowering temperature (Fennema et al. 
1973) cause little increasing trend or almost 
constant in aipha amino nitrogen content; 
but damage to cell during freezing and frozen 
Immediate after 
freezing 
5.11 
13.33 
213.89 
0.84 
8.50 
90 days 
5.12 
15.90 
191.72 
0.88 
8.00 
storage gives rise to drip which carries 
degradation products of protein. Thus net 
balance effect is the slight decreasing trend 
of alpha amino nitrogen content in thawed 
muscle with the increase of drip loss. 
The above results indicate that the bene-
ficial effect of liquid nitrogen freezing over 
conventional plate freezing can exist upto 
59 days only at a commercial storage tem-
perature o.f -l8°C. 
References 
Block, R. J. & Balling, D. (1951) Amino 
Acid Composition of Protein and Foods. 
Springfield, Illinois, USA, 576 
Conway, E. J. (1947) Microdiffusion Ana-
lysis. Revised edn. D. Van Nostrand 
Co. Inc., New York 
Connell, J. J. (1968) In Low Temperature 
Biology of Food Stvjfs. (Hawthorn, J. & 
Rolfe, E. J., Eds.) p. 323, Pergamon 
Press, Oxford 
Fennema, 0. F., Powrie, D. W. & Marth, 
E. H. (1973) Low Temperature Preser-
vation of Foods and Living M after. p. 217, 
Marcel Dekker Inc., New York 
Hill, A. & Gleiw, G. (1973) J. Fd Tech. 
8, 205 
Ironside, J. I. M. & Love, R. M. (1958) 
J. Sci. Fd Agric. 9, 597 
Love, R. M. (1968) In Low Temperature 
Biology of Food Stuff (Hawthorn, J. & 
Rolfe, E. J., Eds.) p. 105, Pergamon 
Press, Oxford 
FISHERY TECHNOLOGY 
ADVANTAGES OF LIQUID NITROGEN FREEZING 47 
Love, R. M. & Iroside, J.I.M. (1958) J. 
Sci. Fd Agric. 9, 604 
Little, A. D. (1958) Flavour Research and 
Food Acceptance, Reinhold Publishing 
Coproration, New York 
Vol. 24, 1987 
MPEDA (1983) Statistics of Marine Pro-
ducts Export. Marine Products Export 
Development Authority, Cochin 
Spinelli, J. & Kemp. B. J. (1966) J. Agric. 
Fd Chem. 14, 176 


Advantages of liquid nitrogen freezing of Penaeus monodon over conventional plate freezing

http://aquaticcommons.org/18622/1/FT24.1_044.pdf

Advantages of liquid nitrogen freezing of Penaeus monodon over conventional plate freezing

Abstract

Similar works

Full text

Available Versions

Aquatic Commons