الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Canning industries are major section of the food industries in
Egypt. So the quality of canned food plays an important of the
consumption, mean while the canned juices preserved by thermal
processing to inactive the highest resistance enzyme and that
treatment affect on the chemical composition of these juices. So the
aim of these studies which include canning of mango, guava and
orange nectars, are as follows:
1- To study the effect of canning processing steps on chemical
composition of nectar.
2- To study the effect of thermal process on enzyme activity of
pectinmethylesterase (P.M.E.), peroxidase (P.O.) and
polyphenoloxidase (P.P.O.).
3- To study the heat penetration of canned nectar to calculate the
parameters of heating and cooling curves.
4- To evaluate the thermal process of canned nectars based on the
highest resistant enzyme.
5- To calculate the required holding time to inactive the highest
resistant enzyme at different initial and retort temperatures.
The results could be summarized as follows: Edible portion of
mango, guava and orange were analyzed for moisture, protein, ash,
ether extract, crude fiber and total carbohydrates; the obtained data
were 82.43, 0.88, 0.31, 0.23, 0.90 and 15.25% for mango; 84.73, 0.96,
0.432,0.306,0.68 and 12.89% for guava and 86.44, 0.32, 0.302,0.13,,- .
0.37 and 11.938% for orange; respectively.
Part 1: Canned mango nectar:
1.1. Effect of canning process on chemical composition:
1.1.1. The total solids and soluble solids were 16.3% and 14.5°Brix
increased to 18.7% and 16.79°Brix after preheating mango
nectar meanwhile no noticeable effect on total and soluble solids
after thermal processing at 91.3°C/35 min. (A)~ 94.9°C/25 min.
(B) and 99.9°C/15 min. (C), was observed.
1.1.2. The acidity ranged from 0.39 to 0.40% (as citric acid), while pH
values ranged from 3.5 to 3.65 after thermal process of mango
nectar.
1.1.3.Ascorbic acid content (Vit. C) was 3.41 mg/IOO g; of raw
mango nectar which decrease after preheating to 1.24 mg/IOO g.
After thermal processing at A, B, C became 1.09, 1.08 and 1.06
mg/IOO g, respectively.
1.1.4. Total sugars were 12.16 and 12.71 for raw and preheated mango
nectar, respectively and ranged from 12.53 to 12.60% after
thermal processing A, Band C. Non reducing sugars were 11.03
and 11.43% for raw and preheated mango nectar, respectively
and ranged from ”10.86 to 11.04% after thermal processing A, B
and C. While reducing sugars were 1.13 and 1.28% for raw and
preheated mango nectar, respectively and ranged from 1.62 to
1.67 after thermal processing at A, B and C.
1.1.5. Carotene content of prepared mango nectar was 0.396 mgIL
which decreased after preheating to 0.374 and ranged from
0.311 to 0.348 mg/L after thermal processing at A, B and C. . .
1.2. Effect of canning processing on enzyme activity:
1.2. 1.Activity of pectin methyl esterase (P.M.E.) was 82.7 (P.M.E. unit
xl06/g) which decreased to 40 (PME Uxl06/g) after preheating
mango nectar. On the other hand it reduced after thermal
processing at A, Band C to 6.3, 6.6 and 10.0 (P.M.E. Uxl06/g),
respectively.
1.2.2. Peroxidase and polyphenoloxidase activity in raw and after
preheating mango nectar were 15.3,2.6 and 0.2 O.D.xI03/min.,
respectively. Thermal processing at A, Band C resulted in no
activity for either peroxidase or polyphenoloxidase enzyme.
1.3. Thermal processing for canned mango nectar were evaluated
on the base of the highest resistance enzyme (P.M.E.):
The percentage of enzyme retention (based an reviewed Z =
11.9°C, D = 0.33 min. and reference temperature 1000C).
1.3.1. Thermal processing at A, Band C reduced the percent enzyme
retention from 100 to 7.36xl0-5, 1.73xlO-7 and 3.89xIO-7%,
respectively, and F values for these thermal process were 2.024,
2.89 and 2.775 min., respectively. While the decimal reduction
of enzyme equivalent to ”F” value used for process calculation
(F/D) were 6.13~ 8.76 and 8.409 for three process, respectively.
1.3.2. Enzyme retention as % of (P.M.E.) at constant initial
temperature 42.2°C were 7.36xlO-s, 5.45xl0-4 and 1.15xl0-6%
for thermal processing A, Band C, respectively. The optimum
holding time for thermal processing A, Band C with constant
initial temperature of 42.2°C to reduce the enzyme retention 0(”
(P.M.E.) to 5.45xlO~4% (F = 1.737 min.) were 32.74~ 25 and
12.72 min. for these treatments, respectively. On the other hand,
calculation of optimum thermal processing time at retort
temperature 90°C were 37.86, 26.70 and 22.70 min. when initial
temperatures was 50, 60 and 70oe; respectively. Also the .
optimum holding time for thermal processing at 1000e retort
temperature were 17.36,16.03 and 13.57 min. at the same initial
temperatures 50, 60 and 70°C, respectively.
1.4. Sensory evaluation for canned mango nectar:
The scores for sensory attributes showed that no significant
difference in texture, colour and overall acceptability of thermal
process mango nectar A, Band C. On the other hand, there are
significant difference in taste and odour for the same processed mango
nectar.
Part 2: Canned guava nectar:
2.1. Effect of canning process on chemical composition:
2.1.1. The total solids and soluble solids were 15.97, 17.28% and
14.82 and 15.52°Brix for raw and after preheated guava nectar,
respectively. After thermal process at 90.4°C/35 min. (A);
95.1°C/25 min. (B) and 99.8°C/15 min. (C) the total solids were
17.45, 17.57 and 17.47% and soluble solids were 15.63, 15.62
and 15.63°Brix for guava nectar, respectively.
2.1.2. The acidity of canned guava nectar ranged from 0.192 to
0.203% (as citric acid), while pH values ranged from 3.39 to
3.34 after thermal process guava nectar.
2. 1.3.Ascorbic acid content (Vit. C) of raw guava nectar was 26.5 mg f’· ”
Vit. CII00 g decrease to 22.83 mg Vit. CIIOO g after
preheating. After thermal processing at A, B, C became 20.0,
21.30 and 22.78 mg Vit. CIlOO g, respectively.
2.1.4. Total sugars of raw and preheated guava nectar were 12.37 and
13.420/0, and non reducing sugars were 10.57 and 11.42%,
respectively, but reducing sugars were 1.80 and 2.00%,
respectively. After thermal processing guava nectar at A, Band ~~ .,
C the total sugars were 13.66, 13.47 and 13.25%; non reducing
sugars were 10.72, 10.54 and 10.43 %, respectively. While
reducing sugars were 2.94, 2.93 and 2.82%, respectively.
2.1.5. Carotene content were 0.174 and 0.091 mg/L for prepared (raw)
and after preheated guava nectar, respectively. After thermal
processing at A, Band C were 0.055, 0.057 and 0.061 mg
carotene/L, respectively.
2.2. Effect of canning processing on enzyme activity:
2.2.1. The pectinmethylesterase CP.M.E.) activity was 135.8 (P.M.E.
unit xl06jg) which decreased to 75 (PME Uxl06/g) after
preheated guava nectar. After thermal processing at A, Band C
reduced to 26.6, 35.0 and 40.0 (P.M.E. Uxl06/g) for guava
nectar, respectively.
2.2.2. Peroxidase and polyphenoloxidase activity in raw and after
preheated guava nectar were 22.5 and 1.4 O.D.xl03/min.
decrease to 0.50 and 0.40 a.D. xlO·3/min., respectively. After
preheated thermal processing at A, Band C resulted in no
activity for either peroxidase or polyphenoloxidase enzyme.
2.3. Thermal processing for canned guava nectar were evaluated
on the base of the highest resistance enzyme (P .M.E.):
The percent of enzyme retention (based an reviewed Z =
16.2°C, D = 0.34 min. and reference temperature 100°C).
2.3.1. Thermal processing at A, Band C reduced the percent enzyme
retention from 1000/0 to 1.76x 10.5
, 3.5x 10.4 and 0.222%,
respectively, and F values for these thermal process were 2.29,
1.855 and 0.902 min., respectively. While (FID) were 6.756;
5.44 and 2.65 for thermal process A, Band C, respectively.
2.3.2. Enzyme retention as % of (P.M.E.) when initial temperature
constant at 45°C were 1.71xlO·3
, 3.5xlO·ifand 3.98% forthennal
processing A, Band C, respectively. The optimum holding time
for thermal processing A, Band e with constant initial
temperature of 45°C to reduce the enzyme retention to
3.5xl0-4% (F = 1.855 min.) were 35.85; 25.0 and 21.28 min. for
three thermal process, respectively. On the other hand,
calculation of optimum thermal processing time at retort
temperature 900e were 39.53,34.63 and 26.94 min. when initial
temperatures was 50, 60 and 70oe; respectively. While the
optimum holding time for thermal processing at 1000e retort
temperature were 28.32, 19.73 and 15.81 min. at the same initial
temperatures, respectively.
2.4. Sensory evaluation for canned guava nectar:
The obtained data showed that no significant difference between
thermal process A, Band C in texture, taste and odour. While theret’
are significant difference in colour and overall acceptability between
these thermal process.
Part 3: Canned orange nectar:
3.1. Effect of canning process on chemical composition:
3.1.1. The total solids and soluble solids of raw orange nectar were
13.850/0and 12.83”Brix increase to 14.030/0and 13.63°Brix
after preheated. After thermal processing orange nectar at
90.2°C/30 min. (A)~ 95°C/20 min. (B) and 100.1°e1l5 min.
results is no noticeable effect on total and soluble solids.
3.1.2. Total acidity and pH values were 0.306, 3.560 and 0.2920/0(as
citric) and 3.55 for raw and after preheated orange nectar,
respectively. After thermal process at A, Band C the acidity
ranged from 0.294 to 0.2950/0and pH values were still at 3.57
for orange nectar.
3.1.3. The level of Vit. C in raw orange nectar was 13.22 mg Vit.
CIl 00 g after preheated became 10.68 mg Vit, CIl 00 g, while
after thermal process A, Band C were decrease to 8.14, 8.43
and 8.86 mg Vit. CII 00 g, respectively.
3.1.4. The total sugars, reducing sugars and non reducing sugars were
11.81, 1.37 and 10.440/0for raw orange nectar, respectively.
After preheating were 12.03, 1.63 and 10.40%, respectively.
While after thermal processing orange nectar at A, Band C
were 12.16; 12.12 and 12.30% for total sugars; 2.17, 1.98 and
1.83% for reducing sugars and 9.99, 10.14 and 10.30 for non
reducing sugars, respectively.
3.1.5. The carotenoids content were 0.35 and 0.23 mg/L for raw and
after preheated orange nectar. After thermal process A, B and.. ’ ..
C were ranged from 0.196 to 0.210 mg/L.
3.2. Effect of canning processing on enzyme activity:
3.2.1. Pectinmethylesterase (P.M.E.) activity were 198.0 and 66.7
CP.M.E. unit x106/g) for raw and after preheated orange nectar,
respectively. Thermal process A, Band C reduced the activity
0.30,4.5 and 16.5 (P.M.E. unit x l O’vg).
3.2.2. Peroxidase (P.O.) and polyphenoloxidase (P.p.a.) activity were
195.0 and 18.0 O.D. xl 03fmin. preheated process led to
decrease these activity to 4.0 and 0.60 a.D. xl O’miin.,
respectively. Thermal process A, Band C resulted in no
activity for either peroxidase or polyphenoloxidase enzymes.
3.3. Evaluation of the thermal process for canned orange nectar
are based on recommended ”F” value 43 min at S2°C with Z
= 7.7SoC that means F iO~8= 0.21 min.
3.3.1. Thermal processing at 90.2°C/min. (A), 95.2°C/20 min. (B) and
100.1 °C/15 min. (C) were resulted in F values of 1.07, 1.92 and
6.66 min, respectively. The optimum holding time were 14.86,
6.29 and 1.05 min at constant initial temperature 45.4°C (on
the base of recommended F i~8 = 0.21 min.) for thermal
process A, Band Cirespectively.
3.3.2. The optimum holding times at initial temperatures 50, 60 and
70°C when retort temperature was 90°C, were I7.41, 16AO and
13.31 min., respectively. While the retort temperature was
lOOce the optimum holding time was 4.63, 4.15 and 2.35 min.
at the same temperatures, respectively.
3.4. Sensory evaluation for canned orange nectar
Sensory evaluation of canned orange nectar processed at A, B, C
was studied. The data showed that no significant difference in order of
the treated orange nectar while are significantly different III the
texture, colour, taste and overall acceptability of orange nectar
processed at A, Band C. The highest scores in texture and colour
were at process B’and C. Also, the highest scores in taste and overall
acceptability were in process (C).