الفهرس 
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Abstract
Two main groups of seventy five Oreochromis niloticus fish each of
weighting 330 ± 20g (yield 150 slice) and 40 Bagrus bayad fish
each of weighting 900 ± 100g (yield 150 slice). The obtained slices
weighting 80 ± 5g and measures (5 x 7 x 1) cm. Every main group
divided into 5 subgroups, 1st (control), 2nd treated by acetic acid
(2%), 3rd treated by citric acid (0.5%), 4th treated by mix of (acetic
acid 2% and citric acid 0.05%) and 5th treated by thyme oil (0.05%)
were subjected to sensory, chemically and microbiologically
examination every three days of refrigerated storage at 4±1 oC till
signs of spoilage became apparent.
Sensory evaluation:
The sensory evaluation in both Oreochromis niloticus and Bagrus
bayad fish fillets aimed to detect appearance, odour, texture and
flavour.
a) Oreochromis niloticus: the results revealed that control.
samples were sensory acceptable about 4-5 days of refrigerated
storage at 4±1 oC, while acetic acid, citric acid, mix and thyme
oil treated samples were sensory acceptable about 12, 8-9, 12
and 7-8 days, respectively.
b) Bagrus bayad: the results recorded that control samples were
sensory acceptable only 4 days of refrigerated storage at 4±1o C,
whereas acetic acid, citric acid, mix and thyme oil treated
samples were sensory acceptable till 7-8, 7, 9 and 6 days,
respectively.
Chemical examination:
(1) pH measurement:
a) Oreochromis niloticus: the mean pH values of control and
acetic acid, citric acid, mix and thyme oil treated samples, were
7.22, 4.78, 6.37, 4.76 and 6.56 at 9th day respectively. Whereas
acetic acid and mix treated samples recoded 6.40 and 6.36 at
15th day, respectively.
b) Bagrus bayad: the mean pH values of control and acetic acid,
citric acid, mix and thyme oil treated samples, were 7.47, 4.92,
6.02, 4.83 and 6.57 at 9th day, respectively. Whereas acetic acid.