الفهرس 
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Abstract
Acrylamide (or acrylic amide) is a chemical compound with the chemical formula C3H5NO. It was accidentally discovered in foods in
April 2002 by scientists in Sweden when they found the chemical in
starchy foods, such as potato chips, French fries, and bread that had been
heated (production of acrylamide in the heating process was shown to be
temperature-dependent). In 1994, the International Agency for Research
on Cancer classified acrylamide as a probable human carcinogen, on the
basis of its carcinogenicity in rodents. Animal studies have shown
positive dose-response relations between acrylamide exposure and cancer
in multiple organs in both mice and rats; included among those organs
were several hormone-sensitive organs, such as the mammary glands and
the uterus.
Shortly after its discovery in food, acrylamide was shown to form in
Maillard reaction, also responsible for the desirable colour and flavour
changes that characterize fried foods. The Maillard reaction involves
numerous reaction pathways and end products, all starting from amino
acids and sugars naturally present in the foods. Acrylamide is formed by
reaction between reducing sugars, for example glucose and fructose, and
one specific amino acid, namely asparagines. Other formation
mechanisms have been reported, for example involving the gluten protein
from wheat, but these are believed to be of minor general importance.
The present study aims to investigate the effect of adding onion peel
powder (OPP) to deep-fat frying process on the formation of acrylamide
(AA) in fried potato slices. Also, the potential mechanisms included in
this context will be in the scope of this study.
The obtained data could be summarized as follow:
I. Antioxidant activity and total phenolics of red onion skin
powder (ROSP)
ROSP showed high antioxidant activity when it was calculated by the
four different methods (AOX, AA, ORR and AAC) used in this study .
Strong antioxidant activity (AA = 90.95±5.34 %) of ROSP is probably
due to its high phenolic content (6984± 65.23 mg GAE.100g-1).
II. Relationship between phenolics content and antioxidant
activity
The total phenolic content of the different ROSP samples
investigated in this study varied from 5101±81.56 to 8203±70.45
mg.100-1 g by the mean of 6984±65.23 mg.100-1 g of dry product. When
all ROSP samples were included in the statistical analysis, there was a
positive and highly significant (p< 0.001) relationship between total
phenolics and antioxidant activity[Total phenolics (mg/100g, d.b.) =
512.0 (Antioxidant activity, %) – 39525 ; R² = 0.902]. This demonstrates
that the high phenolic content of the samples has a significant effect on
the antioxidant activity of the by-product.
III. The effect of onion skin on the fat constant and
malonaldialdehyde (MDA) of palm oil subjected to deep-fat
frying process.
Acid Value
The addition of skin onion leads to decrease the AV of used oil.
Also, the decreasing rates in AV were elevated with the elongation of
subjective period of frying. For example, the AV recorded 6.26, 8.39 and
14.57% after the first day (8 hrs) of treatment which increased by the end
of frying process (3 days, 48 hrs) and recorded 37.43, 39.13 and 46.51%
for the used oil treated with 500, 1000 and 1500 ppm of onion skin
powder (OSP), respectively.
Peroxide value
The addition of skin onion leads to decrease the PV of used oil.
Also, the decreasing rates in PV were elevated with the elongation of
subjective period of frying. For example, the PV recorded 10.24, 9.98 and
23.35% after the first day (8 hrs) of treatment which increased by the end
of frying process (3 days, 48 hrs) and recorded 38.04, 53.43 and 56.25%
for the used oil treated with 500, 1000 and 1500 ppm of onion skin
powder (OSP), respectively.
Malondialdehyde content (MDA)
The addition of skin onion leads to decrease the MDA of used oil.
Also, the decreasing rates in MDA were elevated with the elongation of
subjective period of frying. For example, the MDA recorded 16.02,
24.89 and 28.76 % after the first day (8 hrs) of treatment which increased
by the end of frying process (3 days, 48 hrs) and recorded 33.62, 37.75
and 43.05% for the used oil treated with 500, 1000 and 1500 ppm of
onion skin powder (OSP), respectively.
IV. The effect of red onion skin powder (ROSP) on the
acrylamide content (AA) of palm oil subjected to deep-fat
frying process.
The obtained data indicated that the addition of ROSP leads to
decrease the AA content of used oil. Also, the decreasing rates in AA
were elevated with the elongation of subjective period of frying. For
example, the AA recorded 15.54, 18.07 and 20.17% after the first day (8
hrs) of treatment which increased by the end of frying process (3 days, 48
hrs) and recorded 42.97, 45.78 and 45.78% for the used oil treated with
500, 1000 and 1500 ppm of red onion skin powder (OSP), respectively. It
could be noticed that the concentration of AA in all studied samples were
mostly decreased with the increasing of antioxidants concentration
applied.
In the correlation analysis, important differences were found
between acid value, peroxide value, malonaldehyde content and
acrylamide content of deep-fat frying oils (Table 6 and Figure 5). When
all deep-fat frying oils were included in the statistical analysis, there was
a positive significant (p<0.05 and p<0.01) relationship between fat
constants [acid value (R2 = 0.869), peroxide value (R2=0.881) and
malonaldehyde content (R2= 0.610) and acrylamide content while
relationship between total phenolics content in deep-fat frying medium
and acrylamide content recorded the opposite direction (R2= -0.454 at
p<0.01). The negative relationship between total phenolics content in
deep-fat frying medium and acrylamide content interpreted the potential
effect of antioxidants in ROSP, phenolics, on the formation pathways of
AA in fried potato.
VI.RECOMENDATIONS
In the end of the present work we can submit the following
recommendations:
1- Adding of the plant by-products which acting as natural antioxidants to
deep-fat frying oil samples before frying process in houses,
restaurants, and factories after the present study indicated that the
ability of these compounds to delay the formation of acrylamide (AA)
compounds, potential toxic and carcinogenic compounds during deepfat
frying processes.
2- Desire all the efforts to reduce the presence of some potential harmful,
toxic and carcinogenic compounds i.e. AA which really constitute a
threaten to all population in different community.
3- Make sure that the importance of using the proper and healthy ways
for cooking some commonly foods distributed in the Egyptian local
markets such as meat etc.
4- Up dating and complete the Egyptian standards for the fried foods and
their products to include the newly environmental pollutants such as
AA etc.
5- Encouragemore research in the future to innovative newly natural
antioxidants instead of the chemical ones particularly after many
questions have been raised for their potential role in inducing the
toxic and carcinogenic effects in human being.