الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Seafood is important source of nutrients such as proteins of high biological
value as well as other important nutrient for human. Tilapia fish have high
commercial value because it is widely spread and preferred in Egypt on the
view of its special flavor.
The aim of the present study is direct to evaluate the effect of different
preservation methods viz freezing process, gamma irradiation (1 and 3 kGy),
potassium sorbate (1% and 2%) and Mint oil (1% and 2%) on the microbiological
,chemical properties and organoleptic evaluation of Tilapia (Oreochromis
niloticus) flesh.
The results can be summarized as follows:
1- Microbiological and chemical analyses of fresh tilapia fish:
1.1 The results indicated that total bacterial count, total psychrophillic bacteria, total
mould, Streptococcus faecalis, Staphylococcus aureus and Bacillus cereus were
2.7x10 4 , 2.2 x10 4 , 1.0x10, 4.8x10 2 , 5.6 x10 2 and 3.8x10 2 cfu/g, respectively.
1.2 The results showed that the chemical properties of fresh tilapia fish such as
moisture content, pH, TVBN and TBA were 81.98%, 6.54, 8.48 mg.N/100g and
0.014 OD.
2- Effect of freezing and frozen storage at -18˚C on the microbial load and chemical
properties of tilapia (O. niloticus) flesh:
2.1. The result indicated that the count of all type of the microorganisms tend
to decrease as the storage period increased.
2.2. The results showed that moisture content significant decreased with
increasing the storage period. However pH, TVBN and TBA values significant
increased with increasing storage period.
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3- Effect of irradiation process on the microbial load and chemical properties of
tilapia (O. niloticus ) during cold storage at 4˚C±1:
3.1. Gamma irradiation caused significant decrease in microbial counts. The
decrement in microbial counts increased by increasing the applied dose. In
addition irradiation (1 and 3 kGy) caused complete elimination of total yeast
and mould, and Staphylococcus aureus however Bacillus cereus was eliminated
with 3kGy. It was obvious that Streptococcus faecalis were more resistant than
the other aerobic pathogenic bacteria.
3.2. the results of chemical quality parameters of irradiated samples showed
that the moisture content decreased significantly as the irradiation dose and
storage time increased, the pH value of irradiated samples was found to
increase progressively during storage, the results also indicated that the rate of
increasing in the TVBN during cold storage period was lower at higher dose
than at the lower one and TBA increased linearly to the dose level and there
was a significant increment on TBA of irradiated samples with 1 and 3 kGy
during cold storage period but the increasing rate decrease with the increased
dose.
4- Effect of potassium sorbate on the microbial load and chemical properties of
tilapia (O. niloticus) during cold storage at 4˚C±1:
4.1. Treatment of samples by 1 and 2% potassium sorbate decreased the total
bacterial count, total psychrophillic bacteria, Streptococcus faecalis,
Staphylococcus aureus and Bacillus cereus. In addition to potassium sorbate was
more effective against moulds.
4.2.the results of chemical analyses of samples treated with1 and 2% potassium
sorbate indicated that the moisture content of fish samples treated with
K.sorbate significantly decreased during cold storage period while the pH value
,TVBN and TBA were increased during cold storage period while the rate of
increase was lower in treated fish samples than that of control one.
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5- Effect of Mint oil on the microbial load and chemical properties of tilapia
(O.niloticus) during cold storage at 4˚C±1:
5.1. The result of microbiological test of fish samples treated with 1 and 2%
Mint oil showed that storage at 4˚C±1 considerably increased the total
microbial counts in control which reached around 10 7 cfu/g after 6 days.
However, the total microbial count of treated samples with 2% Mint oil reached
around 10 7 cfu/g after 10 days. Meanwhile, the Mint oil solution caused
decreasing in pathogenic bacteria Streptococcus faecalis, Staphylococcus
aureus and Bacillus cereus initially and during the cold storage period.
5.2. the result of chemical analyses of treated samples with 1% and 2% Mint oil
showed that the moisture content of fish samples treated with 1% and 2% Mint
oil decreased during the cold storage period while pH value, TVBN and TBA
were increased with increasing the cold storage period.
6- Organoleptic evaluation of O. niloticus flesh as affected by gamma irradiation
with 1 and 3 kGy; K sorbate 1 and 2% and mint oil 1 and 2%:
6.1. The results showed that the overall acceptability at zero time were
98.60;96.30’95.30;98.30; 98.0; 94.60 and 93.0% for control; irradiated fillets
with 1 kGy; irradiated fillets with 2kGy; fillets immersed in 1% k-sorbate;
fillets immersed in 2% k-sorbate; fillets immersed in 1% mint oil and fillets
immersed in 2% mint oil, respectively.
6.2 During cold storage period it could be noticed that there was a significant
decrement in the appearance; odor; texture and overall acceptability for all the
treatments under investigation as the storage period increase.
6.3 The panelists rejected the samples at 6th; 26th; 30th; 10th; 14th;10th and 10th for
control; irradiated fillets with 1 kGy; irradiated fillets with 2kGy; fillets
immersed in 1% k-sorbate; fillets immersed in 2% k-sorbate; fillets immersed
in 1% mint oil and fillets immersed in 2% mint oil, respectively for control;
irradiated fillets with 1 kGy; irradiated fillets with 2kGy; fillets immersed in 1%
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k-sorbate; fillets immersed in 2% k-sorbate; fillets immersed in 1% mint oil and
fillets immersed in 2% mint oil, respectively During cold storage.