الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The pre4drying treatments included the application of SOme
blanching and soaking treatments for the purpose of comparing
their efficiency in stopping or decreasing colour change in
the peeled sliced fruits until the completion of steps leading
to their dehydration. The effect of soaking or blanching treatment
was investigated before and after dehydration9 With all
soaking and/or blanching treatments, the dehydration conditions
orveemna)i.ned constant (drying at 600C for 20 hrs in air-circulated
1- A soaking solution of 0.4% NaZS~05 at room temperatureapplied
for 10 and 15 min for peeled s11ced apple and pears, res~
pective1y, induced the best colour in dehydrated materials.
2- Organoleptic evaluation of sun-dried prOducts indicated that
they did not show satisfactory Scores
Overall organoleptic evaluation for 32 dehydration trials
with apple and 18 trials with pears was performed with the
aid o~ trained judges. Organoleptic scores as well as the
visual estimation of these dehydrated products indicated
that Anna apple variety was more acceptable than Baladi
apple and that artificial dehydrated apples were superior
to sun~dried ones. A dipping solution of 0.4% NaZSZOS indaupcpelde
thaendhpiegahress.t organoleptic SCores with both dehydrated
4- All blanching treatments did not show satisfactory results
from the standpoint of colour of dehydrated-blanched fruit
pieces. Although some solutes were found effective in
maintaining or enhancing the colour when used as in_
gredients for preliminary dipping treatments at room
temperature?they did not show any significant influence
upon their use as solutes for blanching treatmen~ possibly
because of the high temperature of blanching.
5- Dehydrated frUits previously blanched at BOoc were found
comparable with their Control samples from the standpoint of
colour, upon using the tested blanching solutions. After
applying the designated soaking treatments (9 treatments),
visual estimation of the soaked peeled frUit pieces revealed
that Using solution of 1% citric acid +0.5% NaCl for 5 min
of dipping gave the best result from the standpoint of
stability of colour. However, increasing dipping period
more than 10 min showed some degree of colour changes.
With both apple and pears, increasing soaking
only 3 min using 1% citric acid and OoS% NaCl
improved colour of dehydrated fruit material
their corresponding control treatments.
7- Solutions of N~2SZ0S alone were found more effective tiffin
NaZSZOS combined with CaClz solution in producing better
colour for dehydrated material, with all soaking period
tested.
period to
solution
compared to
8- Four degrees of dehydration temperature (50, 60, 70, and
SOoC) were compared together with the application of three
different drying intervals (10, 15 and ZO hrs.)~while the
soaking pretreatment was constant (0.4% NaZSZOS for 10 min
with apple and 15 min with pears1were effectivated. Increasing
temperature of dehydration than 700C influenced colour
of both dehydrated fruits with all the drying periodstested,
except in case of using SOOC for 10 hrs 0 Increasing period
of dehydration influenced colour on16 upon using higher
dehydration temperature of 75 and 80 C.
In view of the comparable results obtained for various dehydration
trials tested, from the standpoint of appearance ,
organoleptic properties and induced colour changes in dehydrated
materials, it was decided to continue research on the effect of
some selected optimum conditions on some aspects of physical
dehydration and properties as well as chemical composition of the
obtained dehydrated materials directly after processing and after
certain periods of storage. All treatments which induced higher
organoleptic scores than 82 were selected (13 treatments) which
included those employed 0.4% Na2SZ0S as dipping solution before
dehydration followed by artificial drying at temperatures of 500,
70°, SOoC for 10 hrs; 70°C for IS hrs, in case of both fruits,
and those dehydrated at Soo, 60° and 700C for 20 hrs in case
of apples and 50 and 60°C for 20 hrs in case of pears.
9- Drying ratio of freshly dehydrated samples ranged between
1: 6.2 to 1:6.5 in case of apples and between 1: 5.3 to 1:5.5
in case of pears.
10- The increase in degrees of temperature and in period of
dehydration druing processing resulted in lower moisture
content with all dehydrated products which ranged between
14.98 to 11.45 in case of apples and between 12.908 to
9.989 in case of pears.
11- The increase in aefrees of teaperature and in period of
dehydration dur~1 processing influenced the rehydration
properties. where the higher the extent of these factors
the lower the redehydration values. Rehydration ratioes,
coefficient of rehydration and moisture content (%) in
rehydrated samples ranged between 1:200 to 1:3.0 ; 0.31 to
0.48 and 55.5 to 71.7%, respectively, after soaking dehydrated
apples in water for 1 hrj on the other hand, they
ranged between 1: 1.9 to 1: 2.9 ; 0.35 to 0.55 and 52.6
to 70%, respectively, after 1 hr of soaking dehydrated pears.
12- With both apples and pears, moisture formed the highest
percentage in the chemical composition of fresh peeled
flesh and peels while crude fiber formed the second major
constituent and crude protein represented the third
principal constituent.