الفهرس 
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Abstract
Potato tubers (Solanum tuberosum) Diamant varity were cured under rice strew at ambient air conditions (15-19 ºC/60-75 %RH) for
three weeks (curing period) then the tubers were packed in a net
polypropylene bags and stored in cold rooms at 8-10ºC, 85 – 95% RH
with 0.20 – 0.25% carbon dioxide for three months and analyzed for
moisture, total solids, reducing sugars, total carbohydrate, and sensory
attributes at 15 days intervals. By the end of the cold storage the tubers
were reconditioned by increasing the storage temperature gradually
(within 3 days) to 15-17 ºC.
The reconditioned potatoes tubers were transported to the
factory then washed in two stage (soaking wash – drum washing),
peeled (in steam peeler at 7 par pressure), brushed, cut into 10×10 mm
(water pump cutters), sliver removing , then blanched in tap water at
tow stage (blancher”1” 3 min at 90ºC- blancher”2” at 75ºC for15 min).
Different concentrations of sodium acid pyrophosphates (SAPP)
(1,2,3,4,5,6,7 and 8gm/L ) , sodium metabisulphite (SMBS) (1,2,3,4,5
and 6gm/L), citric acid monohydrate (1,2 and 3gm/L) as well as a
mixture of the previous agents (3gm SAPP /L +1gm CA /L), (3gm
SMBS /L +1gm CA /L), (2gm SAPP /L +1gm CA /L), (2gm SMBS /L
+1gm CA /L) and (1.5gm SAPP /L +1.5gm SMBS /L +1gm -CA /L)
were added to the tap water in the two blanching steps then the strips
were air dried at 90ºC for 15 min, deep fried at 160ºC for 1 min, precooled
for 15min at -3ºC, freezed at -35ºC for15min and stored at -
18ºC. The quality attributes of stored tuber were evaluated during the
curing and cold storage periods. The color of frozen strips and sensory
attributes of the fried potatoes strips as well as the blanching solution
and strips tissue pH were evaluated and the results could be summaries
in the following points:-
1. Chemical composition of potatoes tubers
Diamont potatoes tubers contained 80.30% moisture, 19.70%
dry matter (total solids), 10.31% crud protein , 0.44% crud fat, 2.11%
crud fiber, 4.65% total ash and 82.49% total carbohydrate and 0.48%
reducing sugars (On dry weight basis).
2. Curing
Moisture content decreased from 80.30 to 77.79% after 21 days
of curing this decrease was continued with expanding the curing
period to 45 days (76.06%). The changes of tubers dry matter during
curing had an opposite trends. Total carbohydrates decreased from
82.49% to 80.95% after 21 days of curing and reached to 80.25% after
45 days. On the other hand reducing sugar increased after 21 days of
curing from 0.48% to 0.59% and reached to 0.63% with extending the
curing period to 45 days.
3. Cold storage
The moisture content (77.79%) was decreased by increasing the
cold storage up to 60 days (75.60%) then it began to increase slightly
and reached to 76.10% by the end of storage period (90 days). The dry
matter had an opposite trends to that of moisture. While, reducing
sugar was increased from 0.59 % in cured potatoes to 1.06 after 90 days of cold storage whereas, total carbohydrate decreased from 80.95
(cured potatoes) to 70.9% then it slightly increased to 78.6 %.
1. Effect of after cooking darkening agents:-
1.1. Sodium acid pyrophosphate (SAPP)
The pH of the blanching solutions and tissue decreased from
7.43 and 6.33 (tap water) to 4.03 and 4.53, respectively for the strips
blanched with 8 gm/l SAPP. Increasing of SAPP concentration up to 3
gm/l SAPP improved the colour to light and very light (1.5, 0-00)
while it was not affected by increasing the SAPP concentration over 3
gm/liter.
Organolyptically, the color and taste had the same previous
trend. While, texture, odor and crispiness was not changed by
increasing SAPP concentration.
1.2. Citric acid (CA)
The pH of blanching solution decreased from 7.43 (water
without additives) to 3.30 for the strips blanched with 3 gm /L CA,
also the tissue pH decreased from 6.33 (water) to 4.03 (3 gm/liter).
The color of frozen and fried French fries strips had no change neither
by adding citric acid nor by increasing its concentration. Meanwhile,
increasing the concentration of CA more than 1 gm/L lead to an un
acceptable sour taste. On the other hand odor, crispiness and texture
didn’t affect due to blanching in different concentrations of CA.
1.3. Sodium metabisulphite (SMBS)
The pH of blanching solution decreased from 7.43 for control
(tap water) to 5.07 for the water contained 6 gm SMBS/L also, the pH of potato tissues decreased from 6.33 in control (tap water) to 5.47 (6
gm /L SMBS).
The color of control frozen strips samples was light grey (2.7)
and it improved to medium light (2.4) when blanched in 1gm/L
SMBS. Also, increasing of SMBS concentration up to 4 gm/L SMBS
improved the color to light, very light (1.6, 0-00) while increasing the
concentration of SMBS over 4 gm/L did not affect the color any more.
The color of frozen French fries enhanced (p≤ 0.05) with
increasing of SMBS concentration up to 3 gm/L. Meanwhile,
increasing the SMBS concentration over that did not affect the fried
strip color. On the other hand, increasing of SMBS concentration in
blanching solution had a negative effect on the taste and the odor
while, the texture and crispiness slightly improved by increasing
SMBS concentration up to 3gm/liter.
2. Effect of after cooking darkening agents mixtures
2.1. SAPP / citric mixtures:-
The pH of blanching water decreased from 7.43 (tap water) to
3.23 (3gm SAPP/L + 1gm CA /L). Blanching the strips in 3 gm
SAPP/liter without citric reduced the tissue pH by 11.06 % while
blanching in 3 gm SAPP +1 gm CA /L reduced the pH of strips tissue
by 19.90%.
Organolyptically, the color of frozen French fries stripes
blanched in water was light grey (2.7). The strips color improved to
very light (0.9) with blanching in 3 gm/liter SAPP + 1 gm/L CA. The
color improved (p≤ 0.05) from 7.10 in control to 13.50 with blanching
in a mixture of 3/1 gm/L SAPP, CA respectively. The taste improved
(p≤ 0.05) from 7.92 in control (0/0) to 9.12 with blanching 3/1gm/L. The odor crispiness and texture had no significant change
(P>0.05) neither by adding the SAPP only nor by adding the
SAPP/citric mixture (3gm SAPP/L & 3gm SAPP+1 CA/L).
2.2. Citric acid / sodium metabisulphite.
Blanching the strips in 3 gm SMBS/L without CA reduced the
tissues pH by 7.27% while blanching with 3 gm SMBS +1 gm CA\ L
reduced the tissues pH by 12.64%. The color of frozen French fries
stripes was light grey (2.7) for strips blanched in tap water. The frozen
French fries strips colour improved to light, very light (1.75) with
blanching in 3 gm SMBS + 1gm CA \ L.
The colour improved from 7.10 in control samples to 12.04 with the
mixture of 3gm SMBS+1 gm CA\ L. The fried strips taste, odor,
crispiness, texture had no significant (P>0.05) changes neither added
the SMBS (3 gm/L) only nor by adding (3gm SMBS+1 CA\ L)
compared with control.
2.3. SAPP/SMBS/ CA mixtures
The pH of blanching solution was changed from 7.43 with tap
water to 3.37 by blanching with the mixture of the three agents SAPP,
SMBS and CA by 1.5/1.5/1 gm/L, respectively, while The pH of the
strips tissue was decreased from 6.33 to 5.47.
The frozen French fries strips colour improved from medium,
light grey (2.7) for control strips to (waxed white, very light, 0.7) when
the strips blanched with the mixture of 1.5 gm/L SAPP, 1.5 gm/L
SMBS and 1 gm/L CA.
Sensory evaluation of diamont frozen French fries blanched with
using the mixture of SAPP, SMBA and CA (1.5/1.5/1 gm/L,
respectively) showed that the colour values of frozen French fries strips improved from 7.10 in control samples to 14.06. On the other
hand, the colour of fried strips had significant (P≤0.05) changed in the
samples blanched with all additives concentrations and its mixtures.
The fried strips taste improved from 7.92 in the control sample
to 9.50 with the mixture of 1.5gm SAPP/L+1.5gm SMBS gm/L+1gm
CA /L). Meanwhile, the strips odor slightly increased to 19.02 by
blanching with the mixture of 1.5 gm/L SAPP, 1.5gm/L SMBS and
1gm/L citric acid compared with control (17.80).
The fried strips crispiness and texture did not affect significantly
(P>0.05) by blanching with the ACD agents mixture compared with
control.
Based on overall results, except taste no significant differences
were noted among different concentration of CA alone in this study
while CA-treated samples were rated significantly lower than other
treatments with panelists comments on sour and bitter notes. However
SAPP and SMBS with concentration of 3gm/L significantly improved
the French fries strips quality attribute and colour (less graying) and
overall acceptability. But the mixture of SAPP/CA and SMBS/CA
(2/1gm/L&3/1gm/L, respectively) improved significantly (P≤0.05) the
French fries strips quality (less graying) and improved the taste and the
colour while the best quality was achieved by blanching with the
mixture of 1.5gm/L SAPP +1.5gm/L SMBS+1gm/L CA.