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American Journal of Applied Sciences 6 (7): 1341-1346, 2009
ISSN 1546-9239
© 2009 Science Publications
Corresponding Author: Ruzainah Ali Jaafar, Department of Bioengineering, Section of Biosystem and Bioprocess Engineering Technology,
University Kuala Lumpur-Malaysian, Institute of Chemical and Bioengineering Technology, Taboh Naning,
Alor Gajah, Melaka, Malaysia Tel: 06-5512022 Fax: 06-5512005
1341
Proximate Analysis of Dragon Fruit (Hylecereus polyhizus)
1
Ruzainah Ali Jaafar,
1
Ahmad Ridhwan Bin Abdul Rahman,
1
Nor Zaini Che Mahmod and
2
R.Vasudevan
1
Department of Bioengineering, Section of Biosystem and Bioprocess Engineering Technology,
University Kuala Lumpur-Malaysian, Institute of Chemical and Bioengineering Technology,
Taboh Naning, Alor Gajah, Melaka, Malaysia
2
Molecular Biology Lab, Department of Biomedical Science,
Faculty of Medicine and Health Sciences, University Putra Malaysia, Selangor, Malaysia
Abstract: Problem statement: Dragon fruit (Hylecereus polyhizus) is well known for the rich nutrient
contents and it is commercially available worldwide for improving many health problems. Several
studies show the proximity value of red pitaya fruits but the nutrient composition of the stem has not
been extensively studied. Approach: This study was carried out to measure the proximate analysis of
moisture content, water activity, ash, crude protein, crude fat, crude fiber, glucose and ascorbic acids
content in premature and mature of dragon fruit. The dried powder was produced from the stem of
dragon fruit and the proximate analysis of dragon fruit stem was compared between freeze drying
process and drying oven process. Results: Results of this study showed that 96% moisture; 0.270 g of
protein; 0.552 g L
−1
glucose and 132.95 mg L
−1
ascorbic acid of dragon fruit stem found higher than
the fruit flesh of the dragon fruit. Conclusion: The premature stem had higher values than the mature
stem of the dragon fruit which may helpful in preventing the risk factors of certain diseases.
Key words: Red pitaya, proximate analysis, Malaysia
INTRODUCTION
Dragon fruit or red pitaya belongs to the Cactaceae
family from the subfamily Cactoidea of the tribe
Cactea
[1]
. In Malaysia, the red pitaya or dragon fruit is
commonly called as “buah naga”. Among the red pitaya
species Hylocereus polyrhizus (Red flesh) fruits are
edible and it has a great source of vitamin C and water
soluble fiber
[2]
. Hylocereus polyrhizus is a small fruit
climbing cactus that has received world-wide
recognition as an ornamental plant for its large, scented,
night-blooming flowers. The red skin fruit weighed up
to 1kg has translucent dark-red flesh considered as a
rich source of nutrients and minerals such as vitamin
B1, vitamin B2, vitamin B3 and vitamin C, protein, fat,
carbohydrate, crude fiber, flavonoid, thiamin, niacin,
pyridoxine, kobalamin, glucose, phenolic, betacyanins,
polyphenol, carotene, phosphorus, iron and
phytoalbumin
[3]
. It is also rich in phytoalbumins which
are highly valued for their antioxidant properties
[4]
.
Hylocereus polyrhizus is rich in fibers, vitamin C,
minerals and phytoalbumins which are highly valued
for their antioxidant properties. The dragon fruit helps
the digestive process, prevent colon cancer and
diabetes, neutralize toxic substances such as heavy
metal, reduce cholesterol levels and high blood pressure
and consumed regularly the dragon fruit can help
against asthma and cough. It is also rich with
potassium, protein, fiber, sodium and calcium which
goods for health than other fruits
[5]
. There are three
techniques for foods drying are commonly used such as
sun drying, drying oven and freeze drying. First, the
drying process is heated high to force out the moisture
from food. Secondly, dry air to absorb the released
moisture and finally the air movement to carried out the
moisture away from the food. The freeze dried product
should be passing through all the three stages which are
freezing process, primary and secondary drying
process. Freeze-drying is a technique that results in
high-quality dehydrated products due to the absence of
liquid water and the low temperatures required in the
process. The solid state of water during freeze-drying
protects the primary structure and minimizes changes in
the shape of the product, with minimal reduction of
volume
[6]
. The drying process may alter these
properties, resulting in products with modified texture,
Am. J. Applied Sci., 6 (7): 1341-1346, 2009
1342
optical, thermal and nutritional properties
[7]
. The
rehydration ratio can be considered as a measure of the
injuries caused by the processing and drying to the
material. It is generally accepted that the rehydration
capacity is dependent on the degree of cellular and
structural disruption. According to Jayaraman et al.
[8]
,
during the drying process, irreversible cellular rupture
and dislocation, results in loss of integrity and hence, in
a dense structure of collapsed, greatly shrunken
capillaries with reduced hydrophilic properties, which
are reflected by the inability to imbibe sufficient water
to fully rehydrate. Proximate analysis used to determine
the proximate principles of any substance, as contrasted
with an ultimate analysis. The proximate analysis of
food refers to the analysis of the total content of a food
component, not taking account of the individual
compounds making up that food component. The macro
components are generally analyzed for their proximate
amounts
[9]
. The main objectives of this study was to
produce the dragon fruit stem in powder form using
freeze drying process and to measure the proximate
analysis parameter such as moisture content, water
activity, crude protein, crude fat, crude fiber, ash,
glucose and ascorbic acid between mature stem and
premature stem and also comparing the proximate
analysis of dragon fruit stem between freeze drying
method and drying oven method.
MATERIALS AND METHODS
Sample preparation: The dragon stem was cleaned
and drained off before used. Nearly 200 g of stem was
cut into small pieces using Warring blender (Warring
Commercial, Laboratory Blender) for 2 min and was
homogenized using homogenizer (Heidolph DIAX 900)
with ratio 1:3 w/v and filtered using Muslin Cloth. The
filtrate was transferred into freeze dryer bottle in and
kept at -18°C for four days or at -80°C for two days in
freezer before freeze-drying at -45°C, pressure
86×10
−3
M bar for 4 days. Then the frozen sample was
freeze dried using freeze dryer (LABCONCO, Freeze
Dry System/ FREEZONE 4.5). The freeze dried sample
was kept into a tight container before further analysis.
Moisture, ash, fat, protein content, water activity and
fiber in the sample were determined using method by
AOAC International
[10]
.
Moisture content: The crucible was placed inside
drying oven for 105°C for 2 h. After that, the crucible
was placed in the desiccators for allowing cooling. The
beaker was weighed and 2 g of the powder was placed
in the beaker. The sample was drying in drying oven
(Memmert 600, Germany) for 3 h at temperature
105°C. Then the dried sample was weighed for percent
of dry weight and percent of moisture content in
sample.
Ash: The preparation of ash was same as preparing
crucible in moisture content. Two gram of sample was
put into crucible and weight was recorded and placed in
muffle oven (Furnace Nabertherm, Germany) at 550°C
for 8 h.
Fat: The fat content was determined directly extracting
the dried ground pitaya fruit with petroleum ether in an
intermittent Soxhlet extractor (Soxhlet Extractor
Darmstadt, Germany) and extracted the sample for 4 h.
The residue in round bottom flask after solvent removal
represents the fat content of the sample. The residue
was weight and checks the Reflective Index (RI) using
reflextrometer (Merck KGaA, 64271 Darmstadt,
Germany).
Crude protein: Nitrogen was determined using
micro-Kjeldahl method. About 2 g of dried sample was
transferred into digestion tube by adding 2 tablets of
catalyst and 20 mL of sulfuric acid to digestion in
30 min using Kjeldahl digester (Tecator Kjeltec
System, Germany) at minimum temperature 400°C.
After that, 50 mL distilled water was added for
distillation using Kjeldahl distillation. Then, the sample
was titrated with hydrochloric acid (0.20 N) to calculate
the amount of HCL present in NaOH solution (40%).
The boric acid solution (4%) was used for the catalyst
reagent. The percentages of nitrogen were converted to
protein by multiplying by 6.25.
Water activity: The powder was placed inside the
plastic placing sample. It was measured using A
w
sprint
(Swiss made NOVASINA TH-500) water activity
equipment.
Crude fiber: Two gram of sample was put into 250 mL
conical flask and 1.25% Sulfuric acid solution was
added. The sample was heated about 30 min and was
filtered using vacuum filter (today’s vacuum filtration
VF 100) and washed until traces of acid was undetected
using pH paper. The Whatman paper 5B which pore
size 125 micrometer was placed in the Buchner flask.
After that the acid extracted was transferred into 250 mL
conical flask and 1.25% NaOH solution was added. The
sample was heated again for 30 min and was filtered
using vacuum filter and washed with water until base
was undetected. The whole material was transferred
into crucible and dried for 12 h at 120°C. After that the
crucible was placed into muffle oven at 550°C for 12 h
and weight of crucible was recorded.
Am. J. Applied Sci., 6 (7): 1341-1346, 2009
1343
Ascorbic acid: Five gram of fresh pitaya stem was cut
and homogenized using warring blender. The sample
was filtrated using Muslin cloth. The filtrate will used
to determine the ascorbic acid content using
reflectometer (Merck KGaA, 64271 Darmstadt,
Germany).
Glucose concentration: The glucose concentration was
determined using 2 g of fresh pitaya stem. The sample
was cut into small particles and homogenized using
warring blender. Then, the sample was filtrated using
Muslin cloth and centrifuged with speed of 15000 rpm
for 15 min. The emulsion was analyzed using glucose
analyzer to measure the glucose concentration.
RESULTS
In this study, we determined the method of
production of Hylocereus polyrhizus stem powder using
freeze drying method and the proximate analysis
parameter was carried out using dried sample from
freeze dryer and drying oven. For proximate analysis,
we determined the moisture content, water activity, ash,
crude protein, crude fiber, crude fat determination,
glucose and ascorbic acid. All the analysis was done
through Standard Operation Procedure (SOP) in the
food analysis lab. Table 1 shows the comparison
between the operating system of freeze dyer and drying
oven. The data shows that drying oven was used at
50°C to dry the sample rather than freeze dryer system
was used at -45°C. About 184.02 g initial weight of
sample stem was homogenized using homogenizer with
water ratio 1:3 w/v and dried using freeze dyer at
temperature -45°C and vacuum pressure 89 × 10
−3
M bar.
The final weight was 5.93 g and the weight of moisture
lost was 178.09 g due to high amount of water
contained in the pre mature stem.
Table 2 shows the proximity analysis in dragon
fruit stem. For freeze dried product, the percentage of
moisture content in mature stem was 96.04% and for pre-
mature stem was 97.62%. While, for drying oven
method, the percentages of mature stem was 96.11 and
96.42% for premature stem. Water activity analysis relies
on measuring the amount of moisture in the equilibrated
headspace above the sample, which correlates directly
with sample A
w
. A sample for water activity was placed
in a small closed chamber at constant temperature and a
relative humidity sensor was used to measure the
Equilibrium Relative Humidity surrounding the product
(ERH) of the sample atmosphere after equilibration. A
simple and accurate variation of this approach is the
chilled mirror technique in which the water vapor in the
headspace condenses on the surface of a mirror that was
cooled in a controlled manner. Water activity plays a
main role where it controls the microbial activity and it
keeps the key for the shelf life of the dragon fruit
product especially in stem. The higher moisture content
(high water activity, A
w
) will thus decrease the keeping
quality and the shelf life also shorter. The result shows
the water activities of the mature stem for freeze drying
and drying oven result was in range 0.545-0.563 A
w
.
While, for the pre-mature stem show that the result in
range 0.836-0.865 A
w
. There is a possibility for the
growth of halophilic organisms and xerophilic
organisms for minimum temperature at 25°C in the
stem of dragon fruit.
In this experiment, the percentage of nitrogen was
also calculated using the standard procedure of Kjeldahl
methods and the conversion factor was 6.25. The result
of this analysis showed that 7.18% of mature stem and
14.7% of premature stem using freeze drying product.
While, the percentage by without using freeze drying
product are 6.3% for mature stem and 11.9% for
premature stem. Nitrogen was the most distinguishing
element present in proteins. Figure 1 shows that
percentage of crude protein in premature stem was higher
than the mature stem because, the premature stem has
more nitrogen presented rather than mature stem.
To determine the crude fat, the Soxhlet method was
applied which involved a direct solvent extraction.
Table 1: Comparison of operating system of freeze dryer and drying
oven
Measurement Freeze dryer Drying oven
Temperature -45°C 50°C
Air condition vacuum, cold Fresh air inlet,
Pressure 86×10
−3
M bar hot normal air
Equipment brand LABCONCO, Memmert 600,
Freeze dry system Germany
Duration time 4 days 1 day
Fig. 1: Comparison between mature stem and premature
stem using freeze drying and drying oven
Am. J. Applied Sci., 6 (7): 1341-1346, 2009
1344
Table 2: Moisture content analysis of Hylocereus polyrhizus
Freeze drying Drying oven
------------------------------------------------ ------------------------------------------
Sample Mature stem Premature stem Mature stem Premature stem
Moisture:
Weigh of aluminum dish (g) 54.800 55.160 53.980 54.960
Weigh of aluminum dish with sample before drying (g) 60.350 60.200 58.610 54.960
Weigh of aluminum dish with sample after drying (g) 55.020 55.280 54.160 55.150
Dry Metter (%) 3.960 2.380 3.890 3.580
Moisture content (%) 96.040 97.620 96.110 96.420
Water:
Water Activity (A
w
) 0.563 0.836 0.545 0.865
Temperature (T) 25.3°C 25.5°C 25.7°C 25.2°C
Time (t) 11 min 32 sec 5 min
41 sec 16 min 08 sec 5 min 52 sec
Crude protein
Amount of HCL required to titrate (mL) 10.000 18.600 9.000 15.000
Nitrogen (%) 1.480 2.350 1.010 1.900
Weight of protein (g) 0.144 0.294 0.126 0.238
Protein (%) 7.180 14.700 6.300 11.900
Crude fat:
Thimble + dry sample (g) 46.890 47.050 47.420 47.580
Weight of thimble after extraction (g) 46.800 46.880 47.310 47.350
Weight of fat (g) 0.090 0.170 0.110 0.230
Crude fat (%) 4.500 8.500 5.500 11.500
Reflective index (Brix%) 10.800 28.400 12.500 33.100
Crude fiber
Weight of crucible (g) 17.300 17.000 16.870 17.460
Weight of crucible + fiber (g): 17.350 17.030 16.910 17.480
Weight of fiber (g) 0.050 0.030 0.040 0.020
Crude fiber (%) 2.500 1.500 2.000 1.000
Ash:
Weight of crucible (g) 16.910 17.440 17.010 17.920
Weight of crucible + ash (g) 17.000 17.480 17.100 17.950
Total ash (g) 0.090 0.040 0.090 0.030
Total ash (%) 4.500 2.000 4.500 1.500
The free lipid content consists of neutral fats
(triglycerides) and free fatty acids was determined by
extracting the dried and ground material with light
petroleum or diethyl ether in a continuous extraction
apparatus such as a Soxhlet extractor. The result for the
fat weight in the mature stem and premature stem for
freeze drying method was 0.09 and 0.17 g with
reflective index 8.0 and 28.4% Brix. For without freeze
drying result, weight of the mature stem and premature
stem was 0.11 and 0.23 g with reflective index 12.5 and
33.1% Brix.
Table 2 shows the crude fiber analysis for mature
stem and premature stem in dragon fruit. The result
shows that the percentage of fiber was low in dragon
fruit stem compared to the dietary standard of dragon
fruit flesh. The crude fiber percentage of mature stem
and premature stem using freeze drying are 2.5 and
1.5% while 2.0 and 1.0% for using drying oven. The
standard of high-fiber in food was above 40% or above
0.75 g. The percentage of fiber in mature stem and
premature stem are 4.5 and 2.0% respectively using
freeze drying process and 4.5 and 1.5% respectively for
drying oven process. The result shows that there was a
small amount of minerals left out in the stem. It was
because the content of starches of the stem contains
fiber, phosphate and calcium. Crucible selection was
critical to accurate results but each type of crucible has
its limitations. While platinum crucibles are the best,
they are prohibitively expensive. In Table 2, majority of
premature stem have higher value than mature stem.
The higher parameters for premature stem are moisture
content, water activity, crude protein crude fat, glucose
concentration and ascorbic acid. The higher parameters
for mature stem are crude fiber and total ash because of
little fiber in premature stem of dragon fruit. But the
Dragon fruit stem gets more fiber while growing up
into a mature stem. Figure 1 shows that comparison
between mature stem and premature stem using freeze
drying process and drying oven process.
Basically, the result that has been taken from the
experiment cannot be determined as same as the
standard value of dragon fruit flesh. Half of nutrient in
stem has higher value and another half has lower value.
The higher values for proximate analysis parameter are
moisture content and ascorbic acid. The lower values
for proximate analysis parameter are crude protein,
Am. J. Applied Sci., 6 (7): 1341-1346, 2009
1345
Table 3: Comparison between stem and flesh of dragon fruit
Nutritional contents Flesh Stem
Moisture 82.5-83 g 96.0-98.0 g
Protein 0.159-0.229 g 0.120-0.270 g
Fat 0.21-0.61 g 0.09-0.23 g
Crude fiber 0.7-0.9 g 0.02-0.05 g
Ascorbic acid (vitamin C) 8-9 mg 63.71-132.95 mg L
−1
Ash - 0.03-0.09 g
Water activity (A
w
) - 0.545-0.865 A
w
Glucose - 0.263-0.552 g L
−1
crude fat, crude fiber and analysis. The other parameter
such as glucose, ash and water activity cannot be
determined as a lower or higher because the reference
data cannot find. Table 3 shows comparison between
stem and flesh of dragon fruit. The result shows that a
small different value between freeze drying process and
drying oven process. In this experiment, there are some
different between freeze drying and drying oven. The
differentiation of this process has been shown in Table 3,
which was freeze drying process are used at -45
o
C and
vacuum pressure at 86×10
−3
M bar. For drying oven
process, it was used at high temperature 50°C and
pressure at normal air. In this case, the value of ascorbic
acid has more affected to the others parameter because,
ascorbic acid has a biological role as a reducing agent
in hydroxylation reactions in the body, easily oxidized
by air and easily destroyed by during food processing
with high temperature. The results of this study were
similar to the study done by Khalili et al.
[5]
.
DISCUSSION
Pitaya is commercially cultivated in many parts of
Asia
[11]
and cultivation in Malaysia is more
concerned
[12]
. The pitaya fruit has medicinal value and
increases the excretion of heavy metal toxins and
lowers cholesterol and blood pressure. The peel of
dragon fruit has a high potential to be used as a natural
dye
[13]
. However, ingestion of significant amounts of
red-fleshed dragon fruit may result in
pseudohematuria
[14]
.
This research was carried out from the production
powder from dragon fruit stem using freeze drying
method and the proximate analysis parameters such as
moisture content, water activity, crude protein, crude
fat, crude fiber, ash, glucose and ascorbic acid was
measured using freeze drying product (powder) and
without using freeze drying product (dried with drying
oven). Freeze dried products at lower temperatures
extends their shelf life. The shelf life of a freeze dried
product can be predicted by measuring the rate of
degradation of the product at an elevated temperature.
The drying oven process is used at 50°C and can make
an effect of proximate analysis parameter such as
glucose and ascorbic acid. Based on the result of
sample preparation by production of powder, to ensure
the powder process was success, several parameters
must be controlled such as cooling chamber,
temperature and vacuum pressure. The temperature and
the vacuum pressure must be in low temperature to get
perfect powder. In the manifold method, flasks, impulse
or vials are individually attached to the ports of a
manifold or drying chamber. The product is either frozen
in a freezer, by direct submersion in a low temperature
bath, or by shell freezing, depending on the nature of the
product and the volume to be freeze dried. The pre-
frozen product was quickly attached to the drying
chamber or manifold to prevent warming. The vacuum
must be created in the product container quickly and the
operator relies on evaporative cooling to maintain the
low temperature of the product. This procedure can only
be used for relatively small volumes and products with
high eutectic and collapse temperatures.
CONCLUSION
A well rich nutrient content has the possibility to
prevent various diseases. This study provides that
premature stem of dragon fruit has more nutritional
value than the mature stem. This selection of nutrients
from the premature stem has an important nutritional
quality to improve the benefit for health and therapeutic
potential by targeting the compounds present in the
premature stem. Red pitaya could be considered as a
valuable economic product.
ACKNOWLEDGEMENT
The researchers would like to extend their gratitude
to Prof. Dr. Abu Talib Bin Othman, Deputy Vice
Chancellor (student’s affairs and Technopreneur) of
University Kuala Lumpur (UKL) for sharing his
knowledge, excellent cooperation and support for the
research by providing the samples.
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