3rd International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2013) January 26-27, 2013 Hong Kong (China)
Effect of Vacuum Concentration on the Properties of
Apricot and Peach Juices
A.S.Elhadad, O.M.Alwakdi, A.Abusheta and F.Abdulsalam
Abstract—The effect of concentration under vacuum method on
the physicochemical properties, sensory evaluation and
microbiological load of apricot and peach juices were investigated.
The apricot juice contained significantly higher contents of moisture
content, total acidity, ash and ascorbic acid than those of peach juice.
In contrast, peach juice contained significantly higher contents of
total solids, total sugars, non-reducing sugars and total carotenoids
than those of apricot juice. The colour index and pH value were
significantly higher in peach juice than those of apricot juice. The
concentration under vacuum of apricot and peach juices led to
significant increase in total solids, total soluble solids, colour index,
total sugars, reducing - sugars, non-reducing sugars and ash contents.
The concentration under vacuum led to decrease total bacterial
viable count , moulds and yeasts of apricot and peach juices
Keywords— Vacuum Concentration, Properties, Apricot, Peach
Juices.
I. INTRODUCTION
F
RUIT juices are important sources of nutrients and energy
and they play an important role in human nutrition (
Storey et al., 2006). Fresh fruits and vegetables provide
humans with a set of essential nutrition factors such as sugars,
vitamins, micro and macro elements, polyphenols and
antioxidants (Kranz et al., 2006). Apricot is the third most
widely grown stone crop with a world production of ca.2.8 Mt
in 2005. The production is mainly located in the Mediterranean
countries which collectively account for 40% of global
production (Versari et al., 2008). Apricot fruits are appreciated
by consumers for their flavor, sweetness and juiciness; these
characteristics are strongly related to the variety and ripening
stage at harvest (Botondi et al., 2003).
Peaches are fruits of great commercial importance. Besides
the raw natural fruits, peaches are utilized in the form of
products such as juices, pulp and nectar. During processing of
fruit juices and also during storage, detrimental changes such as
loss of volatile compounds, destruction of vitamins and amino
acids, hydrolysis of carbohydrates, development of undesirable
odours and tastes and browning reactions can occur
(Arslanoglu et al., 2005).
Evaporation of juices is a traditional concentration method.
It is one of the most studied and more used technologies in the
food industry (Nindo et al., 2007).
A.S.Elhadad, O.M.Alwakdi, A.Abusheta and F.Abdulsalam are with
Department of Food Technology, Faculty of Engineering and Technology,
Sebha University, Libya.
Production of concentrated juices contributes to reduce the
needed area for storage and diminishes transport costs per unit
of dry matter. It was reported that concentration of fruit juices
increases production efficiency by a factor of
2-3
(Kovalenko, 1997). Production of fruit juice concentrates is
mainly based on three technologies: heat evaporation,
membrane concentration and cryoconcentration. Evaporation of
juices is a traditional concentration method. It is one of the
most studied and more used technologies in the food industry
(Nindo et al., 2007).
The concentrates of juices may be employed as flavouring
materials in some food products besides consumption after
reconstitution in time of rarity (Abd El-Fadeel, 1981).
Evaporation of excess water in fruit juices is considered to be
the most economical and most widely used method of
concentration (Karel, 1975). The main idea of serum-pulp
separation method is based on low viscosity of the serum,
which substantially increases the heat transfer coefficients,
facilitates concentration and reduces flavour deterioration and
browning (Askar et al., 1981).Afifi (1995). It showed a slight
difference in physical and chemical properties of reconstituted
juices that were concentrated by different conventional methods
or serum-pulp method.
The aim of this investigation was to study the effect the
vacuum concentration method on producing apricot and peach
juice concentrates.
II MATERIALS AND METHODS
A. Materials
Ripe apricot (Prunus armeniaca L) was obtained from
Gherian Governorate and ripe peach (Prunus persicaL) was
obtained from the local market in Sebha City, Libya.
B. Methods
Extraction of juice: Apricot and peach fruits were washed,
cut into halves and the kernels were removed and heated to 80
C. The juice was mechanically extracted using an electrical
blender Model No. BY1 54 FC and strained through two layers
of cheesecloth. Samples of the juice were chemically analyzed.
The extracted juice was pasteurized at 80 C for 10 minutes and
then cooled rapidly to 25 C according to Foda et al. (1970).
Vacuum concentration (V.C.): The apricot and peach
juices were concentrated by rotary evaporator under vacuum
(22 mmHg) at 45-50 C. The concentration process was
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3rd International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2013) January 26-27, 2013 Hong Kong (China)
continued until the total soluble solids (T.S.S.) of the juice
reached to about double folds for apricot and peach juices.
Physicochemical analysis: Moisture, total soluble solids
(T.S.S.), total acidity, ascorbic acid and ash were determined
according to A.O.A.C. (2000). The pH value was measured
using a Inolab level 2 pH meter with glass electrode (Ingold u
456-ku-57) at 25 C as described by A.O.A.C. (2000). Total and
reducing sugars were determined by Lane and Eynon method
as described in the AOAC (2000). Non-reducing sugars were
calculated as follows: non-reducing sugars =(% Total sugars % Reducing sugars) x0.95. colour index was determined
colourimetrically as described by Rangana (1979) at 420nm.
Carotenoids were determined according to Wettestein (1957).
Three replications of all these determinations were carried out.
Microbiological examination: Total viable bacterial count
(TVBC), moulds and yeast (M&Y) and coliform group were
examined according to the methodology of the APHA (1992)
and Oxoid (1990).
Sensory evaluation: Juice was evaluated by ten panelists
for taste, odour, colour, texture and overall acceptability
according to Pastor et al. (1996) and modified by El Mansy,
et al. (2005).
Statistical analysis: Analysis of variance was applied to
chemical composition and sensory evaluation for fresh and
concentrated juices. Data were treated as data for complete
randomization design. Multiple comparisons were carried out
using Least significant difference (L.S.D.) at 0.05 level of
significance (Gomez and Gomez 1984).
III. RESULTS AND DISCUSSION
Physicochemical properties of apricot and peach juices
Data in Table (1) shows the Physicochemical properties of
apricot and peach juices. The apricot juice
contained
significantly higher contents of moisture content, total acidity,
ash and ascorbic acid (86.27, 2.09, 0.57% and 47.13 mg/100 g)
than those of peach juice (85.41, 0.76, 0.49% and 40.91
mg/100g). In contrast, peach juice contained significantly
higher contents of total solids, total sugars, non-reducing sugars
and total; carotenoids (14.59, 8.85, 5.07% and 6.03 mg/ 100g)
than those of apricot juice (13.73, 7.80, 4.27% and 4.79
mg/100g). The colour index and pH value were significantly
higher in peach juice (90.98 AND 4.41) than those of apricot
juice (0.32 and 3.79).
TABLE 1 PHYSICOCHEMICAL PROPERTIES OF FRESH APRICOT AND PEACH JUICES
Properties
Moisture %
Dry matter %
T.S.S. %
pH value
Color index Abs. at 420 nm
Total acidity %
Total sugars %
Reducing sugars %
Non-reducing sugars %
Ash %
Ascorbic acid mg/100g
Carotenoids mg/100g
Juices
Apricot
86.27
13.73
13.17
3.79
0.32
2.09
7.80
3.31
4.27
0.57
47.13
4.79
Effect of vacuum concentration on physicochemicalproperties of apricot and peach juice
Data in Table (2) shows the changes occurred in apricot
and peach juices after concentration under vacuum. The
moisture content of apricot juice decreased significantly by
concentration from 86.27 to 72.78%. On the other hand, dry
matter increased significantly from 13.73% to 27.22%. The
total soluble solids increased significantly from 13.17 % to
26.33%. the pH value of apricot juice increased significantly
from 3.79 to 3.89. The colour index of apricot juice increased
significantly from 0.32 to 1.69. This may be caused by increase
of darkness due to the colour producing during concentration.
These results are in agreement with those reported by Ibrahim
L.S.D.
Peach
85.41
14.59
12.87
4.41
0.98
0.76
8.85
3.51
5.07
0.49
40.91
6.03
0.08
0.08
N.S
0.03
0.03
0.06
0.26
N.S
0.56
0.04
4.86
1.78
(1985), El-Hamzy (1996), Mostafa (2002) and Dyab et.al.
(2003)
Total reducing and non-reducing sugars increased
significantly by concentration from 7.80, 3.31 and 4.27% to
11.76, 5.68 and 5.78% on wet weight basis, respectively. This
increase of sugar content may be due to the evaporation of
water during the concentration. This decrease may be due to
partial destruction caused by heat for ascorbic acid and
degradation through vacuum concentration for carotenoids.
These results agree with those reported by El-Hamzy (1996),
Mostafa (2002) and Dyab et al. (2003).
In the peach juice, moisture content decreased significantly
from 85.41 to 73.00%.On the other hand, dry matter increased
significantly from 14.59 to 27.00%. Total soluble solids
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3rd International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2013) January 26-27, 2013 Hong Kong (China)
increased significantly from 12.87 to 26.00%. The pH value
decreased significantly from 4.41 to 4.23. Colour index
increased significantly by concentration from 0.98 to 2.07,
which could be attributed to increase of pigment concentration.
These results are in agreement with those reported by Sandhu
and Bhatia (1985), El-Hamzy (1996), Mostafa (2002) and
Dyab et al. (2003).
Total reducing and non-reducing sugars increased
significantly from 8.85, 3.51 and 5.07% to 14.52, 6.75 and
7.38%, on wet weight basis respectively. The increase in
reducing sugars may be attributed to the inversion of nonreducing sugar to reducing sugar. These results agree with
those reported by Ibrahim (1970), El-Hamzy (1996), Mostafa
(2002) and Dyab et al. (2003). Total acidity decreased from
0.76 to 0.70%, which might be due to volatilization of some
acids during concentration. Total ash increased significantly
from 0.49 to 0.92%, on wet weight basis by concentration.
Ascorbic acid and total carotenoids in peach decreased
significantly from 40.91 and 6.03 mg/100g to 28.35 and 5.50
mg/100g, on wet weight basis, respectively. The reduction in
ascorbic acid could be attributed due to destruction by heat
concentration while the reduction in carotenoids might be
attributed to degradation during concentration. These results are
in accordance with those given by Sandhu and Bhatia (1985),
El-Hamzy (1996), Mostafa (2002) and dyab et al. (2003).
TABLE 2 PHYSICOCHEMICAL PROPERTIES OF FRESH AND CONCENTRATED APRICOT AND PEACH JUICES.
Properties
Fresh
Moisture %
Dry matter %
T.S.S. %
pH value
Color index Abs. at 420nm
Total acidity %
Total sugars %
Reducing sugars %
Non-reducing sugars %
Ash %
Ascorbic acid mg/100g
Carotenoids mg/100g
0.26
13.73
13.17
3.79
0.32
2.09
7.80
3.31
4.27
0.57
47.13
4.79
Apricot Juice
Vacuum
concentrated
73.00
27.22
26.33
3.89
1.69
2.32
11.76
5.68
5.78
1.16
30.50
4.41
Effect of vacuum concentration on Sensory evaluation of
juices:
Apricot juice:
Data in Table (3) show the results of sensory evaluation for
concentrated apricot juice. The obtained results concerning the
sensory properties are in agreement with those observed by
Sanad (1991), Mir and Nath (1993) and Dyab et al. (2003).
L.S.D
Fresh
85.41
0.47
1.04
0.03
0.19
0.43
0.28
0.29
0.48
0.07
3.78
0.24
0.47
14.59
12.87
4.41
0.98
0.76
8.85
3.51
5.07
0.49
40.91
6.03
Peach Juice
Vacuum
concentrated
72.78
27.00
26.00
4.23
2.07
0.70
14.52
6.75
7.38
0.92
28.35
5.50
L.S.D
86.27
0.26
0.09
0.03
0.07
0.08
0.34
0.35
0.54
0.06
4.73
0.13
Peach juice:
Data in the same table show the effect of vacuum
concentration on the sensory properties of peach juice. It could
be noticed that the high scores of odour, taste and overall
acceptability was observed in fresh juice. The colour, taste,
odour and overall acceptability scores of all treatments
decreased insignificantly during concentration under vacuum.
TABLE 3 SENSORY EVALUATION OF FRESH AND CONCENTRATED APRICOT AND PEACH JUICES.
Properties
Fresh
Colour
Odour
Taste
Texture
Overall Acceptability
9.36
9.27
9.16
8.94
36.73
Apricot Juice
Vacuum
Significant of F
concentrat
value
ed
8.60
Significant
8.37
Significant
8.27
Significant
7.40
Significant
32.64
Significant
Microbiological examination of apricot and peach juices:
Data in Table (4) showed that the total bacterial viable
count (TBVC) of moulds and yeast of fresh apricot and peach
juices were 4.6x10 and 2.9x10 and 7.8x10 and 3.7x10 cfu/g
respectively and decreased to 2.9x10 and 1.6x10 and 6.1x10
and 1.9x10 cf/g for concentrated apricot and peach juices
respectively.
Fresh
9.42
9.18
9.21
9.13
36.94
Peach Juice
Vacuum
Significant of F
concentrat
value
ed
8.60
Significant
8.27
Significant
8.53
Significant
7.84
Significant
33.24
Significant
Coliform group: The coliform bacteria was not detected
either in fresh and concentrated apricot and peach juices.
The obtained results are in agreement with those observed
by Gibryl (1971), Bulgarelli and shelef (1985) and Dyab et al.
(2003).
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3rd International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2013) January 26-27, 2013 Hong Kong (China)
TABLE 4 MICROBIOLOGICAL POPULATION OF FRESH AND CONCENTRATED APRICOT AND PEACH JUICES.
Properties
Fresh
Vacuum
Fresh
concentrated
4.6x10
2.9x10
7.8x10
TBVC
2.9x10
1.6x10
3.7x10
Y&M
Not
Not detected
Not
Coliform
detected
detected
group
Vacuum
concentrated
6.1x10
1.9x10
Not detected
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