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Effect of Gamma irradiation and frozen storage on microbial quality of Rainbow trout (Oncorhynchus mykiss) fillet

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Abstract

The effect of gamma radiation (1, 3 and 5 kGy) on microbial quality of farmed rainbow trout (Oncorhynchus mykiss) fillets which were stored under frozen conditions (-20° C) was studied by measuring microbiological changes in 5 months. Gamma irradiation and increasing of frozen storage time had significant effects (P<0.05) on the reduction of microorganism's population. The total count showed that all samples maintained acceptable microbiological quality until the end of the fifth month of frozen storage. The lowest microbial load at the end of the fifth month of frozen storage was related to irradiated samples at 3 kGy (2 Log CFU/g). Yeasts and molds were below the detection levels in both irradiated samples at 1 and 5 kGy until the end of the third month and in irradiated samples at 3 kGy throughout the frozen storage. The population of yeasts and molds increased in irradiated samples at 1 and 5 kGy in the fourth and fifth month of frozen storage. Growth of coliform bacteria and Salmonella wasn't observed in control and irradiated samples due to good hygienic quality of fish breeding, fishing, handling, filleting and packaging and also effect of freezing on elimination and inactivation of mesophilic microorganisms.
Received: January 2010 Accepted: Agust 2010
84 Iranian Journal of Fisheries Sciences 10(1) 75 - 2011
Effect of Gamma irradiation and frozen storage on microbial
quality of Rainbow trout (Oncorhynchus mykiss) fillet
Oraei, M.1*; Motalebi, A. A.2; Hoseini, E.1; Javan, S.3
Abstract
The effect of gamma radiation (1, 3 and 5 kGy) on microbial
quality of farmed rainbow
trout
(Oncorhynchus mykiss) fillets which were stored under frozen conditions
(-20°
C) was
studied by measuring microbiological changes in 5 months. Gamma irradiation and
increasing of frozen storage time had significant effects (P<0.05) on the reduction of
microorganism's
population. The total count showed that all samples maintained acceptable
microbiological quality until the end of the fifth month of frozen storage. The lowest
microbial load at the end of the fifth month of frozen storage
was
related to irradiated
samples
at 3 kGy (2 Log CFU/g). Yeasts
and molds
were below the detection levels
in
both
irradiated samples at 1 and 5 kGy until the end of the third month and in irradiated samples
at
3 kGy throughout the
frozen storage. The population of
yeasts and molds increased in
irradiated samples at 1 and 5 kGy in the fourth
and fifth month of frozen storage. Growth of
coliform bacteria and Salmonella
wasn't
observed
in control and irradiated samples due to
good hygienic quality of fish breeding, fishing, handling, filleting and packaging and also
effect of freezing on elimination and inactivation of mesophilic microorganisms.
Keywords:
Gamma irradiation,
Frozen Storage,
Rainbow
trout (Oncorhynchus mykiss),
Microbiological analysis
__________________
1- Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, P.O.BOX: 14155-
4933, Tehran, Iran.
2- Iranian Fisheries Research Organization, P.O.BOX: 14155-6116 Tehran, Iran.
3- Iranian Fish Processing Research Center. Bandar Anzali, Iran.
*Corresponding Author: (email addresses: Marjan.Oraei@yahoo.com
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radiation (
76 Oraei et al., Effect of Gamma irradiation and frozen storage on microbial……
Introduction
The rainbow trout (Oncorhynchus mykiss)
belongs to the Salmonidae and is one of
the main fish species farmed in Iran. The
demand for rainbow trout in Iran and other
country markets has increased significantly
over the past decade and this could be due
to its desirable characteristics (taste,
aroma, white flesh) resulting in a high-
quality product and nutritional value
(FAO, 2010a,b; Iranian Fisheries
Organization, IFO, 2009). The major
problem of distribution of seafood or
fishery products is their susceptibility to
spoilage, mainly due to contamination of
spoilage and pathogenic microorganisms
(Özden and Erkan, 2010). Fish spoilage
occurs following growth and activity of
special microorganisms and lipid oxidation
which cause off-odor and off-taste by
production of some metabolites changing
sensory characteristics and customer
acceptability (Moini et al., 2009;
Rostamzad et al., 2010). Therefore there is
an obvious need for development of new
technologies and efficient fish preservation
methods which permit shelf-life extension
of these products (Chouliara et al., 2004).
Besides traditional methods such as ice
storage, rapid chilling, freezing, smoking
and heating (Farkas, 1990, 1999;
Himelblooom et al., 1994), various
methods involving the use of organic
acids, antimicrobials (Al-Dagal and
Bazarra, 1999; Gelman et al., 2001),
antioxidants (Haghparast et al., 2010),
edible coating (Motalebi et al., 2010),
modified atmosphere packaging
(Masniyom et al., 2002) and ionizing
Savvaidis et al., 2002;
Chouliara et al., 2004; Erkan and Özden,
2007) have been proposed to extend the
shelf-life of fish and fisheries products.
The irradiation of food products is a
physical treatment involving direct
exposure to electron or electromagnetic
rays, for their long time preservation and
improvement of quality and safety
(Mahindru, 2005). Cobalt-60 (60Co)
produces electromagnetic γ-rays which
have too much energy. During radiation,
DNA molecules undergo swelling and
break alongside the chain, preventing them
from functioning normally. As a result, the
parasites and microorganisms that have
been affected are no longer capable of
reproducing themselves and they die
(Lacroix and Ouattara, 2000). Therefore
food irradiation provides safety and
extends the shelf life of fisheries products
because of its high effectiveness in
inactivating pathogenic and spoilage
microorganisms without deteriorating
product quality (Özden and Erkan, 2010).
The alteration in microbial population and
composition as a result of irradiation
depends on the dose of irradiation, storage
temperature, packaging conditions and fish
species (Özden et al., 2007). Freezing
controls growth of microorganisms and
biochemical changes in fish as a
preservation method for long time storage
(Motalebi et al., 2010). When irradiation is
used in combination with freezing, the
irradiation doses can be reduced through
synergistic action without affecting the
product quality (Lacroix and Ouattara,
2000). A review of the scientific and
technical literature revealed some
information about the effects of irradiation
on microbiological characteristics of
irradiated food (Lamuka et al., 1992;
Dogbevi et al., 1999; Thayer and Boyd,
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Iranian Journal of Fisheries Sciences, 10(1), 2011 77
2000; Ouattara et al., 2001, 2002; Badr,
2004; Chouliara et al., 2004; Javanmard et
al., 2006; Özden et al., 2007; Sedeh et al.,
2007; Fallah et al., 2008; Turgis et al.,
2008 ; Ahmed et al., 2009; Moini et al.,
2009).
The aim of this study was to
determine the effect of gamma irradiation
process in low-dose (1, 3 and 5 kGy) and
frozen storage on microbial quality of
rainbow trout fillets.
Materials and methods
A total of 10 kg freshwater rainbow trout
(Oncorhynchus mykiss) with an average
weight of 300-500 grams were obtained
from a local aquaculture farm located at
Saravan-Foman road, in the north of Iran.
The fish were then transferred to the
laboratory at the National Fish Processing
Technology Research Center at Anzali
port in Iran. After passing into rigor
mortis, the fish were washed with tap
water, skinned, beheaded, gutted and then
filleted by a sterile scalpel and washed
again. Each fish was divided into four
fillets (about 70-80 g each). Each fillet was
separately placed in a plastic film bag. The
fillets were divided into four lots (20 fillets
in each lot): 0 kGy (control) and irradiated
samples (1, 3 and 5 kGy) (Moini et al.,
2009). Packed samples were delivered to
the radiation plant in insulated polystyrene
boxes with ice/fillets weight ratio to 2:1.
The ice was placed in plastic film bags.
Gamma irradiation was carried out in the
Nuclear Research Center for Agriculture
and Medicine, Karaj, Iran. Fish samples
were gamma irradiated using a 60Co source
irradiator (Gamma cell Px-30, dose rate
0.23 Gy sec-1). The applied dose levels
were 0 (control), 1, 3, and 5 kGy (Moini et
al., 2009). During irradiation the packed
fish were next to sealed ice covering. The
dose rate was established using alanine
transfer dosimeter. After irradiation,
irradiated and non-irradiated fillets were
transported to the laboratory at the
National Fish Processing Technology
Research Center at Anzali port in Iran in
insulated polystyrene boxes with ice-fillets
weight ratio to 2:1. In the laboratory, fillets
were exposed to rapid freezing in a spiral
freezer (Koppens SVR C400/17-50, UK).
Fillet depth reached to -20° C within 25
minutes. Then frozen fillets were kept in a
cold storage at -20° C for 5 months.
Rainbow trout fillets were analyzed for
microbiological quality at the first day of
frozen storage as 1-month sampling
intervals for 5 months. The first day of the
first interval was registered as day zero.
For the microbiological analysis 10 g of
rainbow trout fillet was removed with a
sterile scalpel and minced under aseptic
conditions. Then it was homogenized for 2
minutes with 90 ml of 0.1% (w/v) sterile
peptone water (Merck, Germany) using a
lab-blender 400 stomacher (Seward
medical, UK). Subsequent dilutions were
prepared by mixing a 1-ml sample with 9
ml of sterile peptone water. All analyses
were carried out in duplicate. For
determination of total bacterial count, 1 ml
of appropriate dilutions were poured-
plated with melted plate count agar (PCA)
(Merck, Germany) and then were
incubated at 35-37° C for 48 h. For the
numeration of total coliforms, 1 ml of
appropriate dilutions were poured-plated
with melted violet red bile agar (VRBA);
plates were incubated at 37°C for 48 h.
Total yeasts and molds were enumerated
on potato dextrose agar (Merck, Germany)
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78 Oraei et al., Effect of Gamma irradiation and frozen storage on microbial……
after incubation at 25° C for 35 days. For
detection of Salmonella spp., 10 g of the
sample was homogenized with 90 ml
lactose broth (Merck, Germany) and
incubated at 35° C for pre-enrichment.
Selective enrichment was performed in
tetrathionate broth (Merck, Germany) at
43° C for 24 h and selenite cystine broth
(Merck, Germany) at 35° C for 24 h
followed by plating on Salmonella-
Shigella (SS) agar (Merck, Germany) and
brilliant-green phenol-red lactose sucrose
(BG) agar (Merck, Germany) incubated at
35° C for 24 h. Suspected colonies
developed on each plate served to
biochemical and serological analysis
(American Public Health Association,
APHA, 1992).All data from microbial
analysis were subjected to factorial
analysis of variance (ANOVA) and
Duncan's multiple range test (P<0.05) to
evaluate the effect of irradiation and
different applied doses in this study and
frozen storage time on microbiological
characteristics of rainbow trout fillets.
Differences between means were
considered significant when P<0.05. SPSS
version 18.0 was used for statistical
analysis.
Results
The values of total count, yeasts and molds
count, coliforms count and Salmonella
detection of non-irradiated (control) and
irradiated (1, 3 and 5 kGy) rainbow trout
fillets during frozen storage (-20° C) are
shown in Table 1.Initial total bacterial
counts of the control samples were 4.38
Log CFU/g, whereas the counts in samples
irradiated at 1 kGy were 3.45 Log CFU
and in irradiated samples at 3 and 5 kGy
were not detectable at day 0 of frozen
storage. Microbial load of irradiated
samples at 5 kGy until the end of the first
month and in the irradiated samples at 3
kGy until the end of the fourth month were
below detection level.
Table 1: Microbial flora count (Log CFU/g) in non-irradiated and irradiated (1, 3 and 5 kGy) of rainbow
trout fillets during frozen storage (-20° C)
Microbial Flora Radiation Dose
(kGy) Storage Time (Month)
0 1 2 3 4 5
Total Count
0 4.38±1.53 aw 3.65±0.06 a
bw
3.30±0 aw 3.65±0.06 aw 3.30±0 aw 3.45±0.21
bw
1 3.45±0.21 ax 3.23±0.33
abx
2.00±0 ax 2.45±0.21 ax 2.00±0 ax 2.69±0.12
b
x
3 ND ay 2.00±0
ab
yND ay ND ay ND ay 2.00±0
b
y
5 ND az ND abz 2.00±0 az 1.00±1.41 az 2.00±0 az 2.47±0
bz
Yeasts and
Molds
0
1 ND ND ND ND ND ND
ND ND ND ND 1.00±0 1.00±0
3
5 ND ND ND ND ND ND
ND ND ND ND 1.00±0 1.15±0.21
Coliforms
0 ND ND ND ND ND ND
1 ND ND ND ND ND ND
3 ND ND ND ND ND ND
5 ND ND ND ND ND ND
Salmonella
0
1 ND ND ND ND ND ND
ND ND ND ND ND ND
3
5 ND ND ND ND ND ND
ND ND ND ND ND ND
ND = not detected; a-b Means within a row, which are not followed by a common superscript letter(s) are
significantly different (P<0.05); w-z Means within a column, which are not preceded by a common superscript
letter(s) are significantly different (P<0.05).
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Iranian Journal of Fisheries Sciences, 10(1), 2011 79
The lowest microbial load at the end of the
fifth month of frozen storage was related
to irradiated samples at 3 kGy (2 Log
CFU/g). Yeasts and molds were not
detected in irradiated samples at 3 kGy
throughout the frozen storage time and in
irradiated samples at 1 and 5 kGy until the
end of the third month of frozen storage.
The population of yeasts and molds
increased in irradiated samples at 1 and 5
kGy in the fourth and fifth month of frozen
storage.
Coliform and Salmonella bacteria
were not detected in all irradiated and
control samples throughout the storage.
Discussion
Although it is widely accepted that the
initial microbial load of freshwater fish
varies depending on water conditions and
temperature, most of the available
literature on different freshwater species
(Tilapia, Striped bass, Rainbow trout,
Silver perch and Sea bream) reports
bacterial counts of 2 to 7 Log CFU/g
(Moini et al., 2009). The initial counts and
the counts in all the time during the frozen
storage indicated to an acceptable fish
quality, considering the proposed upper
acceptability limit for total bacterial counts
of 2×107 CFU/g for fresh and frozen fish
(ISIRI, 1999).
The results of total microbial count
showed that microbial load of irradiated
samples (at 1, 3 and 5 kGy) were
significantly (P<0.05) lower than controls
throughout the storage period. This finding
confirms the significant effect (P<0.05) of
irradiation on the reduction of microbial
count. Food spoilage microorganisms are
generally very susceptible to irradiation; a
90% reduction of most vegetative cells can
be accomplished with 11.5 kGy (Brewer,
2009). In irradiated samples the highest
and lowest microbial counts were related
to 1 and 3 kGy, respectively. Because the
highest radiation dose in this study (5 kGy)
might induce lipid oxidation. These
reaction metabolites made a good media
for microbial growth. In this study
increasing frozen storage time caused a
significant (P<0.05) reduction effect on
microbial count. Freezing is known to
reduce viable cell counts by 1-2 Log units,
with extended storage causing additional,
time dependent reductions (Yammamoto
and Harris, 2001).
Moini et al. (2009) reported that
irradiation at 1, 3 and 5 kGy had a
significant reduction effect on the total
viable count of rainbow trout fillets.
Ahmed et al. (2009) in evaluating the
efficiency of gamma radiation (3, 5 and 8
kGy) in combination with low temperature
(-20° C) storage of degutted fresh Pampus
chinensis, reported that total bacterial
count (TBC) was affected by the radiation.
In their study, initial bacterial load of
control was maximum (1.3×104 CFU/g)
followed by 3 kGy irradiated fishes (2×102
CFU/g) and at 5 and 8 kGy the samples
were completely sterilized resulting in no
bacterial growth. TBC values in their
investigation suggest that the irradiated
samples remain acceptable after 90 days at
-20°C. Sedeh et al. (2007) reported that
irradiation (0.5, 1, 2 and 3 kGy) and
storage at low temperature had a
significant reduction effect on microbial
loads of bovine meat. They reported that
the combined effect of irradiation and
frozen storage was more effective than
each treatment alone on decreasing total
bacteria counts. Javanmard et al. (2006)
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80 Oraei et al., Effect of Gamma irradiation and frozen storage on microbial……
reported that irradiation (0.75, 3 and 5
kGy) and freezing storage (-18°C) had a
significant reduction effect on microbial
loads of chicken meat. The combination of
frozen storage plus irradiation resulted in
greater overall reductions of microbial
loads, extending shelf life of chicken meat
for commercial application and critical
conditions. Jørgensen and Hansen, (1965)
reported that the irradiation of vacuum-
packed gutted trout at 2 kGy a total viable
aerobic count of 106 CFU/g was not
reached within 4 weeks in ice storage. At
doses of 1 and 0.5 kGy this count was
reached after 26 and 23 days, respectively.
Non-irradiated fish which were spoiled in
the third week of ice storage reached a
count of 106 CFU/g after 15 days.
According to my results, yeasts and
molds were not detected in irradiated
samples at 3 kGy throughout the frozen
storage time and in irradiated samples at 1
and 5 kGy until the end of the third month
of frozen storage. It has been stated that
yeasts and molds are sensitive to the
irradiation process because of their large
genomic structure (Fallah et al., 2010).
Because of some metabolite production in
lipid oxidation and bacterial growth
reactions in 5 and 1 kGy, the population of
yeasts and molds increased in the fourth
and fifth months of frozen storage. Ahmed
et al. (2009) reported that in evaluating the
efficiency of gamma radiation (3, 5 and 8
kGy) in combination with low temperature
(-20° C) storage of degutted fresh Pampus
chinensis, the total mold count (TMC)
increased with the increase of storage
period. So that TMC values were 3.1×105,
5.3×103, 3.8×104 and 3.5×104 CFU/g in
control, 3, 5 and 8 kGy treated samples
respectively at the end of 90 days. Fallah
et al. (2008) reported that the irradiation
dose of 1.5 kGy reduced the initial counts
of yeasts and molds by 2 Log units, while
at 3 kGy yeasts and molds were below the
detection levels during 6 days of storage.
Badr (2004) reported that irradiation of
rabbit meat at 1.5 and 3 kGy significantly
reduced the counts of yeasts and molds by
84% and 94%, respectively. H2S-
producing bacteria such as Salmonella are
generally predominant in spoiled fish flora
(Moini et al., 2009). Because of good
hygienic quality of production, fishing,
handling, filleting, washing and packaging,
coliform bacteria and Salmonella were not
detected in irradiated and control samples.
Radiation sensitivity of non-sporeforming
pathogenic bacteria such as Salmonella in
meat and fishery products is well
documented (Badr, 2004; Fallah et al.,
2008; Moini et al., 2009). Like other gram
negative bacteria, Salmonella and
coliforms have a very low resistance to
radiation. Therefore elimination of these
bacteria by radiation could be beneficial to
the preservation of fish products in view of
the major role that these species play in the
spoilage of fish (Moini et al., 2009). In
addition, rainbow trout fillets were
exposed to quick-freezing and then stored
at -20° C. About 90% of bacteria are
present in fish die at the time of freezing.
These bacteria such as Salmonella spp. are
related to the mesophilic bacteria group.
Psychrophilic bacteria that survive in cold
conditions are inactive until fish are frozen
due to absence of free water for their
growth and activation (Johnstone et al.,
1994). Moini et al. (2009) have reported
that the H2S-producing bacteria in the
control rainbow trout samples reached a
maximum count of 4.89 Log CFU/g on
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Iranian Journal of Fisheries Sciences, 10(1), 2011 81
day 35 and were not observed at dose
levels of 1, 3 and 5 kGy for 7, 21 and 42
days, respectively. Fallah at al. (2008)
have reported that no coliforms were
detected in irradiated (1.5 and 3 kGy)
camel meat during refrigerated storage at
3±1° C. Sedeh et al. (2007) reported that
the optimum dose of gamma radiation in
order to decrease coliforms and specially
for elimination of Salmonella of red meat
was obtained at 3 kGy. With an increase in
irradiation, the number of coliforms
decreased. therefore irradiation
significantly reduced them. Also
irradiation and frozen storage was more
effective than each treatment alone at
decreasing coliform counts. Javanmard et
al. (2006) reported that at the first day of
frozen storage Salmonella Typhimurium
was found in one non-irradiated chicken
meat. However at irradiated samples (0.75,
3 and 5 kGy) no Salmonella was observed.
Irradiation and frozen storage was reported
more effective than each treatment alone at
decreasing total and coliform counts. Badr
(2004) reported that irradiation at 1.5 kGy
was not enough for complete elimination
of Salmonella of rabbit meat, while at 3
kGy Salmonella was not detected.
According to all obtained data from
microbial analysis, low-dose gamma
irradiation (especially 3 kGy) can be
applied for microbial control and the safety
of rainbow trout and shelf life extension in
frozen state. Gamma irradiation at 3 kGy
was more effective than irradiation at 1
and 5 kGy in eliminating microorganisms
of rainbow trout fillets. In addition, the
current study showed the synergistic effect
of two preservation methods, food
irradiation and freezing in low temperature
on extending the shelf-life of rainbow trout
fillet by reducing the microorganism's
load.
Acknowledgments
This study was supported by Iranian
Fisheries Research Organization. We wish
to thank National Fish Processing
Technology Research Center at Anzali
port in Iran for performing the experiments
and Atomic Energy Organization of Iran,
Karaj Nuclear Research Center for
Agriculture and Medicine for performing
the irradiation.
References
Ahmed, K., Hasan, M., Alam, J., Ahsan,
N. Islam, M. and Akter, M. S., 2009.
The effect of Gamma Radiation in
Combination with Low Temperature
Refrigeration on the Chemical,
Microbiological and Organoleptic
Changes in Pampus chinensis
(Euphrasen, 1788). World Journal of
Zoology, 4(1), 9-13.
Al-Dagal, M. M. and Bazarra, W. A.,
1999. Extension of shelf-life of whole
and peeled shrimp with organic acid
salts and bifidobacteria. Journal of food
protection, 62, 5156.
American Public Health Association,
1992. Compendium of Methods for the
Microbiological Examination of Foods
third ed. Washington, DC.
Badr, H. M., 2004. Use of irradiation to
control foodborne pathogens and extend
the refrigerated market life of rabbit
meat. Meat Science, 67, 541-548.
Brewer, M. S., 2009. Irradiation effects on
meat flavor: A review. Meat Science,
81(1), 1-14.
Chouliara, I., Savvaidis, I. N.,
Panagiotakis, N. and Kontominas, M.
G., 2004. Preservation of salted,
vacuum-packaged, refrigerated sea
Archive of SID
www.SID.ir
82 Oraei et al., Effect of Gamma irradiation and frozen storage on microbial……
bream (Sparus aurata) fillets by
irradiation: microbiological, chemical
and sensory attributes. Food
Microbiology, 21, 351359.
Dogbevi, M. K., Vachon, C. and Lacroix,
M., 1999. Physicochemical and
microbiological changes in irradiated
fresh pork loins. Meat Science, 51, 349-
354.
Erkan, N. and Özden, Ö., 2007. The
changes of fatty acid and amino acid
compositions in sea bream (Sparus
aurata) during irradiation process.
Radiation Physics and Chemistry,
76(10), 1636-1641.
Fallah, A. A., Tajik, H., Razavi Rohani,
M. and Rahnama, M., 2008. Microbial
and Sensory Characteristics of Camel
Meat during Refrigerated Storage as
Affected by Gamma Irradiation.
Pakistan Journal of Biological
Sciences, 11(6), 894-899.
Fallah, A. A., Saei-Dehkordi, S. and
Rahnama, M., 2010. Enhancement of
microbial quality and inactivation of
pathogenic bacteria by gamma
irradiation of ready-to-cook Iranian
barbecued chicken. Radiation Physics
and Chemistry, 79(10), 1073-1078.
Farkas, J., 1990. Combination of irradiation
with mild heat treatment. Food Control.
1, 223-229.
Farkas, J., 1999. Radiation processing: an
efficient means to enhance the
bacteriological safety of foods. New
Food, 2, 31-33.
Food and Agriculture Organization,
2010a. Cultured Aquatic Species
Information Programme Oncorhynchus
mykiss. Food and Agriculture
Organization, Fisheries and Aquaculture
Department, FAO Publication series.
Food and Agriculture Organization,
2010b. National Aquaculture Sector
Overview Iran (Islamic Republic of).
Food and Agriculture Organization,
Fisheries and Aquaculture Department,
FAO Publication series.
Gelman, A., Glatman, L., Drabkin, V. and
Harpaz, S., 2001. Effects of storage
temperature and preservative treatment
on shelf-life of the pond-raised
freshwater fish, silver perch (Bidyanus
bidyanus). Journal of food protection.
64, 15841591.
Haghparast, S., Kashiri, H., Shabanpour,
B. and Pahlavani, M. H., 2010.
Antioxidant properties of sodium
acetate, sodium citrate and sodium
lactate on lipid oxidation in rainbow
trout (Oncorhynchus mykiss) sticks
during refrigerated storage (4°C).
Iranian Journal of Fisheries Sciences,
9(1), 73-86.
Himelbloom, B. H., Crapo, C., Brown, E.
K., Babitt, J. and Repond, K., 1994.
Pink salmon (Oncorhynchus gorbuscha)
quality during ice and chilled seawater
storage. Journal of food quality, 17,
197210.
Institute of Standards and Industrial
Research of Iran (ISIRI)., 1999. Fresh
and frozen fish and shrimp,
microbiological properties. National
standard No. 2394-1.
Iranian Fisheries Organization, 2009.
Iranian yearbook Fishery and
Aquaculture Statistics. Iranian Fisheries
Publication.
Javanmard, M., Rokni, N., Bokaie, S. and
Shahhosseini, G., 2006. Effects of
gamma irradiation and frozen storage
on microbial, chemical and sensory
quality of chicken meat in Iran. Food
Control, 17, 469473.
Johnston, W. A., Nicholson, F. J., Roger,
A. and Stroud, G. D., 1994. Freezing
and refrigerated storage in fisheries.
Archive of SID
www.SID.ir
Iranian Journal of Fisheries Sciences, 10(1), 2011 83
Food & Agriculture Organization.
Fisheries and Aquaculture Department.
ISBN: 9251035792.
Jørgensen, V. and Hansen, P., 1965.
Storage life of vacuum-packed iced
trout. II. - Influence of radiation
pasteurization. Journal of the Science of
Food and Agriculture, 17(3), 140-141.
Lacroix., M. and Ouattara, B., 2000.
Combined industrial processes with
irradiation to assure innocuity and
preservation of food products - a
review. Food Research International,
33, 719-724.
Lamuka, P. O., Sunki, G. R., Chawan, C.
B., Rao, D. R. and Shackelford, L. A.,
1992. Bacteriological Quality of Freshly
Processed Broiler Chickens as Affected
by Carcass Pretreatment and Gamma
Irradiation. Journal of Food Science,
57(2), 330-332.
Mahindru, S. N., 2005. Food preservation
and irradiation. Aph Publishing
Corporation. chapter 8-11, 13.
Masniyom, P. Benjakul, S. and
Visessanguan, W., 2002. Shelf-life
extension of refrigerated sea bass slices
under modified atmosphere packaging.
Journal of science of food and
agriculture, 82, 873880.
Moini, S., Tahergorabi, R., Seyed Vali, H.,
Rabbani, M., Tahergorabi, Z., Feas,
X. and Aflaki, F., 2009. Effect of
Gamma Radiation on the Quality and
Shelf Life of Refrigerated Rainbow
Trout (Oncorhynchus mykiss) Fillets.
Journal of food protection, 72(7), 1419-
1426.
Motalebi, A. A., Hasanzati Rostami, A.,
Khanipour, A. A. and Soltani, M.,
2010. Impacts of whey protein edible
coating on chemical and microbial
factors of gutted kilka during frozen
storage. Iranian Journal of Fisheries
Sciences. 9(2), 255-264.
Ouattara, B., Giroux, M., Yefsah, R.,
Smoragiewicz, W., Saucier, L., Borsa,
J. and Lacroix, M., 2002.
Microbiological and biochemical
characteristics of ground beef as
affected by gamma irradiation, food
additives and edible coating film.
Radiation Physics and Chemistry, 63,
299-304.
Ouattara, B., Sabato, S. F. and Lacroix,
M., 2001. Combined effect of
antimicrobial coating and gamma
irradiation on shelf life extension of pre-
cooked shrimp (Penaeus spp.).
International Journal of Food
Microbiology, 68, 19.
Özden, Ö. and Erkan, N., 2010. Impacts of
gamma radiation on nutritional
components of minimal processed
cultured sea bass (Dicentrarchus
labrax). Iranian Journal of Fisheries
Sciences, 9(2), 265-278.
Özden, Ö., Inugur, M. and Erkan, N.,
2007. Effect of different dose gamma
radiation and refrigeration on the
chemical and sensory properties and
microbiological status of aqua cultured
sea bass (Dicentrarchus labrax).
Radiation Physics and Chemistry, 76,
11691178.
Rostamzad, H., Shabanpour, B.,
Kashaninejad, M. and Shabani, A.,
2010. Inhibitory impacts of natural
antioxidants (ascorbic and citric acid)
and vacuum packaging on lipid
oxidation in frozen Persian sturgeon
fillets. Iranian Journal of Fisheries
Sciences, 9(2), 279-292.
Savvaidis, I. N., Skandamis, P.,
Riganakos, K., Panagiotakis, N. and
Kontominas, M. G., 2002. Control of
natural microbial flora and Listeria
Archive of SID
www.SID.ir
84 Oraei et al., Effect of Gamma irradiation and frozen storage on microbial……
monocytogenes in vacuum-packaged
trout at 4 and 10° C using irradiation.
Journal of food protrction, 65, 515522.
Sedeh, F. M., Arbabi, K., Fatolahi, H. and
Abhari, M., 2007. Using gamma
irradiation and low temperature on
microbial decontamination of red meat
in Iran. Indian Journal of Microbiology,
47, 7276.
Thayer, D. W. and Boyd, G., 2000.
Reduction of normal flora by irradiation
and its effect on the ability of Listeria
monocytogenes to multiply on ground
turkey stored 7°C when packaged under
a modified atmosphere. Journal of food
protection, 63(12), 1702-1706.
Turgis, M., Han, J., Borsa, J. and Lacroix,
M., 2008. Combined effect of natural
essential oils, modified atmosphere
packaging, and gamma radiation on the
microbial growth on ground beef.
Journal of food protection, 71(6), 1237-
43.
Yammamoto, S. A. and Harris, L. J.,
2001. The effects of freezing and
thawing on the survival of Escherichia
Coli O157:H7 in apple juice.
International Journal of Food
Microbiology. 67, 8996.
Archive of SID
www.SID.ir
... Maintaining the freshness and meat quality of rainbow trout (Oncorhynchus mykiss), which are a member of the Salmonidae family and commonly farmed species in Iran due to their rapid growth and adaptability to various temperatures and water qualities (Oraei et al. 2011) during storage is a significant issue for the food industry due to their susceptibility to chemical and microbial spoilage. The fatty acid composition of rainbow trout varies significantly depending on its diet and typically contains high levels of monounsaturated (29.6%-45.2%) ...
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Rainbow trout (Oncorhynchus mykiss) is a freshwater fish susceptible to chemical and microbial spoilage, limiting its shelf life. This study aimed to enhance and extend the rainbow trout fillets' shelf life stored at 4°C ± 1°C through an immersion treatment using ultrasound‐assisted, defatted pine nut (Pinus gerardiana Wallich) extracts at concentrations of 1% and 2% (w/v), compared to the control group (0% pine nut). Evaluations were conducted at storage intervals of 0, 4, 8, 12, 16, and 20 days. The methodology assessed antioxidant activity through 2,2‐diphenyl 1‐picrylhydrazyl radical scavenging, which showed a linear increase with pine nut extract concentration, reaching 59.24% at 2%. Chemical indicators, such as peroxide values, thiobarbituric acid values, free fatty acids, and total volatile basic nitrogen, decreased significantly (p ≤ 0.05) with higher concentrations of pine nut extract, with the lowest values recorded at 2% across all storage days. Microbial analysis showed a significant reduction (p ≤ 0.05) in the total viable count, psychrotrophic bacteria count, lactic acid bacteria, Enterobacteriaceae, and H₂S‐producing bacteria with increasing pine nut concentrations, with the 2% treatment yielding the lowest microbial loads throughout storage. Sensory evaluation indicated that higher pine nut concentrations improved the acceptability of color, odor, and taste (p ≤ 0.05). However, significant degradation (p ≤ 0.05) in chemical, microbial, and sensory parameters occurred with prolonged storage duration. In conclusion, the 2% pine nut extract was the most effective immersion treatment for extending the shelf life of rainbow trout fillets for up to 12 days.
... The total viable mesophilic aerobic bacteria count (TVMC) is considered as an indicator of fish fillet quality and good manufacturing practices (Özyurt et al., 2015). Several studies performed on rainbow trout fillets in different countries have shown TVMCs ranging from 1.543 log CFU per g to 6.3 log CFU per g (Oraei et al., 2011;Özyurt et al., 2015;Pao et al., 2008;Pullela et al., 1998;Ucak et al., 2020). Ozyurt et al. (2015) defined that TVMCs ranging from 3.06 log CFU per g to 3.31 log CFU per g could indicate a high fish quality which are in agreement of our values. ...
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... The present data are in accordance with those published by Mahmoud (2004). The decrease in total bacterial count during storage period can be attributed to freezing which is known to reduce viable cell counts by 1-2 Log units, with the increase of storage time, and the reduction in viable cell was increased Oraei et al. (2011). Salmonella sp., Shigella sp., E. coli, Staphylococcus sp. and Clostridium sp. ...
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... The present data are in accordance with those published by Mahmoud (2004). The decrease in total bacterial count during storage period can be attributed to freezing which is known to reduce viable cell counts by 1-2 Log units, with the increase of storage time, and the reduction in viable cell was increased Oraei et al. (2011). Salmonella sp., Shigella sp., E. coli, Staphylococcus sp. and Clostridium sp. ...
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The imported frozen (Mackerel) Scomber scombrus was evaluated for the changes of its quality during freezing storage at-18ºC for four months and its compliance with the Egyptian standard specifications. It was found that the protein, lipid and ash contents decreased during the storage period. Furthermore, moisture slightly increased during the storage period. The results also indicated that the samples did not exceed the permissible limits of total nitrogen as determined by the Egyptian Organization for Standardization and the quality of production. Microbiological examination showed a significant decrease [P˂0.05] in the total bacterial count between the first and fourth months of storage. Staphylococcus spp. was detected in the first and the second months of surface examination, being 104.70 cfu×10 3 /g and 2.74 cfu×10 3 /g, respectively. In addition, Salmonella was detected in the first month of surface examination. E. coli and Clostridium were absent in all examined samples. Fourteen different bacterial isolates were isolated from all samples. Twelve isolates were isolated from staph 110 medium and two isolates were found on the SS agar medium. Twelve isolates were coccoid shaped bacteria and 2 isolates were spore forming long rods. All isolates were gram positive. Two isolates were spore forming and twelve isolates were non-spore forming. Six isolates were considered as Staphylococcus sp. and another six isolates were considered as Micrococcus sp. the last two isolates were considered as Bacillus sp.
... Для каждого конкретного продукта определяется не только возможность и режимы РО, но и эффективность применения новых образцов источников ионизирующего излучения [15; 16]. Так, для антимикробной обработки охлажденных рыбы и рыбопродуктов экспериментальные исследования позволили установить оптимальный диапазон доз облучения (1-3 кГр) [17][18][19][20][21][22][23][24][25]. В большинстве случаев этого достаточно, чтобы снизить количество микроорганизмов, вызывающих порчу, примерно на 1-3 log КОЕ/г. ...
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This study was carried out to investigate the rate of lipid oxidation in fresh rainbow trout (Onchorhynchus mykiss) and in the sticks treated by (2.5% w/v) sodium acetate (NaA), sodium citrate (NaC) and sodium lactate (NaL). The pH value, free fatty acid (FFA), thiobarbituric acid (TBA) and sensory evaluation (odor, flavor and color) were determined on 0, 3, 6, 9 and 12 days of storage. The results showed that TBA and FFA in control were significantly higher than those in the other groups (P<0.05). Sticks immersed in NaA indicated a significant difference in formation of free fatty acids in comparison with other sodium salt-treated samples on 9 and 12 days after storage. Sticks dipped in NaL had a maximum level of pH at the end of the storage, whereas samples treated by NaA achieved significantly the lowest value of pH, 9 days after storage. Organoleptic assessments of the samples expressed more acceptability of sticks immersed in sodium salt solutions than the control after 3 days of storage. These indicated that sodium salts, particularly sodium acetate, have antioxidant properties.
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This study was aimed to investigate effects of aqueous citric acid (CA) and ascorbic acid (AA) on lipid oxidation in comparison with effect of vacuum packaging in order to find better treatment to delay improper changes in the Persian sturgeon (Acipenser persicus) fillets during frozen storage due to lipid oxidation. In this study traditional packaging, vacuum packaging, ascorbic acid solution (0.5 %) and citric acid solution (0.5 %) were considered as treatments. Rancidity development was measured by several biochemical indicators including Free Fatty Acids, Peroxide values and Thiobarbituric acid. Also pH, expressible moisture and sensory properties were measured during 6 months storage. Results showed that free fatty acid (FFA), primary and secondary oxidation products of control samples were significantly higher than those in other treatments (p<0.05). Also, expressible moisture and pH value of treated samples were significantly lower than those in control (p<0.05). However both antioxidants (AA and CA) extended shelf life of frozen fillets but rancidity development in CA treated samples was higher than other samples during storage. Results showed that all three treatments had significant effect on delaying lipid oxidation (p<0.05) but usage of AA and vacuum packaging had the best effect on delaying lipid oxidation and increasing shelf-life of fillets (p<0.05). Thus the employment of AA and vacuum packaging alone or in combination with other protective strategies is recommended.
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The current interest in "minimally processed foods" has attracted the attention for combination of mild treatments to improve food safety and shelf-life extention. The present study was conducted to evaluate the combined effect of gamma irradiation and incorporation of naturally occurring antimicrobial compounds on microbial and biochemistry characteristics of ground beef. Ground beef patties (23% fat) were purchased from a local grocery store (IGA, Laval, Que., Canada) and divided into 3 separate treatment groups: (i) control (ground beef without additive), (ii) ground beef with 0.5% (w/w) ascorbic acid, and (iii) g-round beef with 0.5% ascorbic acid and coated with a protein-based coating containing selected spices. Samples were irradiated at 0, 1, 2, and 3 kGy final dose at the CIC. Samples were stored at 4degreesC and evaluated periodically for microbial growth, total thiobarbituric reactive substances (TBARS) and free sulfydryl content. At the end of the storage period, Enterobacteriaceae, Lactic acid bacteria, Pseudomonas and Brochothrix thermosphacta were enumerated. Regardless of the treatment group, irradiation significantly (p less than or equal to 0.05) reduced the total aerobic plate counts (APC). Irradiation doses of 1, 2, and 3 kGy produced immediate reduction of 2, 3, and 4 log units of APCs, respectively. Also, shelf-life periods were higher for ground beef samples containing food additives. Lactic acid bacteria and Brochothrix thermosphacta were more resistant to irradiation than Enterobacteriaceae and Pseudomonas. Concentration of TBARS and free sulfydryl concentrations were stabilized during post-irradiation storage for samples containing ascorbic acid and coated with the protein-based coating containing spices.
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Gamma irradiation can be used as one of the most efficient methods to reduce microorganisms in food. The irradiation of food is used for a number of purposes, including microbiological control, insects control and inhibition of sprouting and delay of senescence of living food. The aim of this study was to study effects of gamma irradiation, refrigeration and frozen storage as the combination process for improvement of red meat shelf-life. The bovine meat samples were treated with 0, 0.5, 1, 2 and 3 kGy of gamma irradiation and kept in refrigerator for 3 weeks and in freezer for 8 months. The control and irradiated samples were stored at 4-7°C and at -18°C for refrigeration and frozen storage, respectively; and microbial and chemical analyze was done at 1 week and 2 months intervals. In this study the optimum dose of gamma radiation in order to decrease the total count of Mesophilic bacteria, Coliforms, Staphylococcus aureus and especially for elimination of Salmonella was obtained at 3 kGy. Microbial analysis indicated that irradiation and storage at low temperature had a significant effect on the reduction of microbial loads. There was no significant difference in chemical characteristics during freezing storage in bovine meat. Also, irradiated meat samples (3 kGy) were stored in 4-7°C for 14 days, compared to 3 days for non irradiated samples.
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In the case of fungi, heat treatment preceding irradiation usually results in a greater antimicrobial effect of the combination process compared with heating after irradiation. The usefulness of mild heat treatment prior to low-dose irradiation has been demonstrated for extending the shelf-life of certain fruits and cereal products, preservation of fruit juices and some other processed fruit products, and for inactivation of toxigenic moulds on nuts, dried fruits, cocoa beans and maize. With bacterial sproes, pre-irradiation followed by heating proved to be synergistic. This combination may be utilized for preservation of foods where heat resistance of bacterial spores is a critical factor. The radiation-damaged bacterial spores in irradiated dry food ingredients have been shown to be more easily destroyed by normal heat processing of complex foods containing such ingredients. In specific cases simultaneous application of heat and radiation (thermoradiation) might be considered for an enhanced destruction of microbes. Thermal stress can also complement or potentiate the effectiveness of radiation disinfestation.
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Pink salmon were stored up to ten days in ice, chilled seawater (CSW), transferred from ice to CSW and from CSW to ice, and evaluated by chemical, physical, microbiological, and sensory methods. The sensory quality of CSW-held fish declined at a faster rate than for iced fish. CSW-held fish had higher weight gain, higher salt and hypoxanthine levels and had softer texture than iced fish. Microbial counts were highest for iced fish and a two-log increase occurred during storage. Moraxella species were predominant in the microbial flora of iced fish whereas Pseudomonas species were predominant in the microbial flora of CSW-held fish. Ice was superior to CSW for maintaining salmon quality.
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The effect of CO 2 ‐enriched atmosphere in combination with either oxygen or nitrogen on the keeping quality of seabass slices stored at 4 °C was investigated. The inhibitory effect on bacterial growth increased proportionally to the CO 2 concentration in the packaging, maximum inhibition being achieved with 100% CO 2 ( P < 0.05). Seabass slices stored in CO 2 ‐enriched atmosphere had lower total volatile base, trimethylamine, ammonia and formaldehyde contents than those stored in air ( P < 0.05). However, increases in lightness and exudate loss were observed for samples packaged in high‐CO 2 atmosphere, suggesting the denaturation of both muscle and pigment proteins by carbonic acid formed. Thiobarbituric acid‐reactive substances (TBARS) increased as the CO 2 concentration increased ( P < 0.05). However, odour, flavour and overall acceptability of CO 2 ‐enriched packaged samples, particularly with 80 and 100% CO 2 , were acceptable throughout storage for 21 days. Chemical and microbial changes in all samples were generally in agreement with sensory panel evaluations. The shelf‐life of seabass slices packaged in 80–100% CO 2 atmosphere could be extended to more than 20 days at 4 °C, compared with 9 days for those packaged in air. © 2002 Society of Chemical Industry
Article
Chicken carcasses dipped in whey fermented by Streptococcus thermophilus, lactic acid solution or water and irradiated at 2.5 kGy by 60Co were evaluated for bacteriological quality on day-1, day-3 and at 3-day intervals for an 18-day storage (4°C) period. Unirradiated carcasses treated similarly were used as control. Gram negative bacteria, Yersinia and Campylobacter counts were significantly (p<0.01) lower in irradiated samples, but no significant (p>0.05) differences were observed among the dipping solutions. Salmonellae were completely eliminated in irradiated samples. Whey fermented by 5. thermophilus reduced the proportion of Salmonella contaminated carcasses from 67% to 20%. As evidenced by the bacterial counts the shelf-life was found to be 15 days for irradiated carcasses compared to about 6 days for the unirradiated samples.