الفهرس 
I. IntroductionOnly 14 pages are availabe for public view
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Abstract
Agricultural and food industries in the Arab world represent
a large proportion of waste was estimated at18.14 million tons
per year and represent remnants of fruit and vegetables many
facture about 6.14% of this amount. Waste in the food industry
is characterized by a high ratio of product-specific waste.
Processing of fruits, vegetables, and oilseeds may results in high
amounts of waste materials such as peels, seeds, stones and
oilseed meals. Disposal of these materials usually represents a
problem that is further aggravated by legal restrictions. Plant
waste is prone to microbial spoilage; therefore, drying is
necessary before further exploitation. The cost of drying,
storage, and transport poses additional economical limitations to
waste utilization. Therefore, agro-industrial waste often is
utilized as feed or fertilizer. However, demand for feed or
fertilizer varies and depends on agricultural production.
Moreover, valuable nutrients contained in agro-industrial wastes
are lost. Thus new aspects concerning the use of these wastes as
by-products for further exploitation on the production of food
additives or supplements with high nutritional value have gained
increasing interest because these are high-value products and
their recovery may be economically attractive.
Therefore, the objective of this work is to analyze some
plant by-products including potatoes and prickly pear peels that
constitute to waste for their nutraceutical values as food
ingredient thus reducing its contribution to environmental
pollution. Also, utilization of such by-products for their
recovery of dietary fibers, phenolics and antioxidants in the
production of snacks such crackers will be in the scope of this
study.
To achieve these aims, the plan of study was prepared as
follow: 1) Potato peel powder (PPP), and Prickly pear peel
powder (PPPP) were prepared and their chemical and physical
properties as well as antioxidant activity were determined. 2)
The rheological properties for both wheat flour control sample
and samples with additions of selected food by-products were
determined by using of farinograph and extensograph tests, and
3) Cracker samples were prepared. Formulation of the Cracker
is applied as follow: wheat flour, 100 g; shortening, 9.64 g; salt,
2.02 g; sodium bicarbonate,0.16 g; yeast, 3.48 g and water 50 g.
Yeast was mixed with water (25 0C) to form a suspension, to
which the other ingredients were then added and kneaded to
form smooth dough. Substitution of wheat flour with prickly
pear peel powder (PPPP) and potato peel powder (PPP) were
conducted based on 5% of the weight of the wheat flour. The
dough was later proofed for 2 hours in a proofer, followed by
sheeting to 1.0mm thickness using a dough sheeter. The dough
was then cut into squares measuring 3cm x 3cm and ‘docked’
prior to baking at 170 0C for 15 min. The sensory evaluation and
antioxidants content for both cracker control samples and
samples with additions of selected food by-products were
determined by using of the specific methods.
The obtained data are summarized as follow:
I. Antioxidant activities and total phenolics in selected food
by-products
I.1 Antioxidant activities of selected food by-products
The by-products powder showed considerable differences in
antioxidant activity (AA = 71.05 - 83.22 %) when it was
calculated by the four different methods used in this study.
potato peels powder (PPP) showed strong activity because of its
high phenolic content (1388 mg EGA.100g-1 DW)while prickly
pear peel powder (PPPP) showed relatively low content in both
antioxidant activity and the total phenolics (421 mg EGA.100g-
1). The decrease in absorbance of β-carotene in the presence of
different methanolic tested food by-products extracts (and wellknown
antioxidants used as standards) with the oxidation of β-
carotene and linoleic acid, antioxidant stability, indicated that
PPP recorded the lowest decreasing followed by PPPP. The
values of PPP absorbance through 120 min are coming well i.e.
corresponding to the line of 50 mg.L-1 of α-tocopherol and upper
to the line 50 mg.L-1 of BHT. By the same manner, PPPP is
coming close to the line of 50 mg.L-1 of BHT. These data
proved the high stability of the all tested food by-products when
comparing with that more common standards, BHT and α-
tocopherol.
I.2 Relationship between bioactive compounds and
antioxidant activity
In the correlation analysis, important differences were
found between phenolics, carotenoids and antioxidant activity of
food by-products. When all food by-products were included in
the statistical analysis, there was a positive significant (p≤ 0.05)
relationship between total phenolics in PPPP (r2 = 0.636), total
phenolics in PPP (r2 = 0.834), total carotenoids in PPPP (r2 =
0.531), total carotenoids in PPP (r2 = 0.593) and antioxidant
activity. These correlations confirm that phenolic compounds
with carotenoids are mainly responsible for the antioxidant
activity of the tested by-products. Also, these data indicates that
many other bioactive compounds beside phenolics and
carotenoids such vitamins, fibers, minerals etc. probably
contribute in the antioxidant activity of the tested by-products.
II. Analysis of selected food by-products
II.1 Proximate chemical composition
The proximate chemical composition of selected food byproducts
showed that the moisture content was ranged 5.71-
6.04%, total protein was 2.42 -10.54 %, crude fat was 0.69 -0.98
%, crude fiber was 7.84 -11.56 %, ash content was 3.12 -4.83 %
and total carbohydrate content was 66.09- 80.22%. With the
exception of carbohydrates, the PPP was recorded the highest
content of the all chemicals components and could be a good
source of protein, fiber and minerals.
II.2 Physical properties
The water (WHC) and oil (OHC) holding capacity of the
tested food by-products noticed that PPP recorded the higher
WHC than PPPP being 8.01and 5.33 g H2O.g-1, respectively,
indicating that the higher fiber content in PPP hold more water
compared to the PPPP. The behavior was recorded for the OHC.
In similar study, the WHC and OHC of ROSP recorded the
highest WHC followed by cauliflower leaves powder (CLP),
PPP and MPP being 9.13, 8.39, 8.24 and 6.03 g H2O.g-1,
respectively.
II.3 Total dietary fiber, carotenoids and phenolics contents
Total dietary fiber, carotenoids and phenolics contents of
food by-products showed that the total dietary fiber content was
ranged 39.53 and 45.91 g.100g-1, total carotenoids was 217.11
and 135.76 mg.100g-1 and total phenolics was 421 and 1388 mg
EGA.100 g-1 for PPPP and PPP, respectively The PPP was
recorded the highest content of total dietary fiber and total
phenolics while PPPP recorded the highest values of total
carotenoids.
III. Effect of tested food by-products on the rheological
parameters
III.1 Farinograph parameters
The incorporating of tested food by-products in dough
increased the water absorption from 57.11% for control to 58.81
and 61.99% for dough contained 5% PPPP and PPP,
respectively. The dough development time and dough stability
increased from 2.7 to 3.3 and 3.9 min with 5% incorporation of
PPPP and PPP, respectively this may be due to high content of
dietary fibers in all of these by-products and pectin which act as
a food hydrocolloid PPPP. The increasing dough development
time illustrates that the dough with the addition of tested byproducts
a longer relaxation time (the dough is tougher). Dough
stability in minutes is the most important index for dough
strength. Addition of tested food by-products, PPPP and PPP, to
flour samples showed markedly longer stability periods than the
control samples (flour without addition of food by-products).
This affect was significantly with the addition of 5% of tested
food by-products for wheat flour. from the viewpoint of dough
farinograph quality number (FQN), statistically significant
difference was found between the control sample (flour without
the addition of the tested food by-products) and the dough with
additions of 5% of tested food by-products (P < 0.05). It is
meaning that an improvement in the quality of the dough
occurred after the addition of 5% tested food by-products, when
the FQN value significantly increased in comparison with the
control sample.
III.2 Extensograph parameters
Dough strength (Extensibility) determined by the area
under the curve and is proportional to energy needed to bring
about rupture. The incorporating of tested food by-products in
dough increased the extensibility from 171 mm for control to
179 and 187 mm for dough contained 5% PPPP and PPP,
respectively.
IV. Analysis of crackers enriched with tested plant byproducts
IV.1 Sensory evaluation
The PPPP and PPP crackers were significantly different
(p≤0.05) in colour. The PPP crackers were shown to be the least
liked by the panelists. For colour, among the tested food byproducts,
the colour of PPPP crackers was rated the highest
(7.10) by the panelists. The desirable colour of crackers is
mainly due to the Millard browning during baking. However, in
PPPP crackers, the colour could be partially contributed by the
carotenoid in PPPP flour which imparts a yellowish colour to
the crackers. Crispiness is perceived when food is chewed
between molars, and is usually expressed in terms of hardness
and factorability. In this study, there was no significant
difference (p≤0.05) in crispiness amongst the different samples
with different composite flour cracker types. However, the PPP
crackers were significantly different (p≤0.05) in overall
acceptance.
IV.2 Bioactive components and antioxidant activity of
control and composite flour crackers
The bioactive components and antioxidant activity of
control and enriched crackers with the tested by-products. The
total dietary fiber, carotenoids and phenolics content in crackers
114
increased from 5.89, 3.01 and 110.23 to 8.11, 14.34 and 143.28
with 5% incorporation of PPPP and 8.74 g.100g-1, 7.88 mg.g-1
and 192.79 mg EGA.g-1 with 5% incorporation of PPP,
respectively. In parallel, the antioxidant activity (AA) in control
crackers was 30.11% which increased to 38.14 (26.67 as % of
change) and 42.07 % (39.72 as % of change) with the
incorporation of PPPP and PPP by 5%, respectively. Tested byproducts
enriched crackers showed strong activity probably due
to their high bioactive compounds (carotenoids and phenolics)
content.