JOURNAL OF THE DRYLANDS 6(1): 429-433, 2016
EVALUATION OF FRUIT QUALITY OF GUNDA GUNDO ORANGE IN
CONTRAST TO OTHER ORANGE FRUITS
Wendm Ygzaw 1, Getachew Hruy 1, Negash Aregay1, Mereseit Hadush2, Eyasu Abraha3,
Kindeya Gebre-Hiwot4
Wendm Ygzaw, Getachew Hruy, Negash Aregay, Mereseit Hadush, Eyasu Abraha, Kindeya Gebre-Hiwot (2016):
Evaluation of fruit quality of Gunda Gundo orange in contrast to other orange fruits. Journal of the Drylands, 6(1):
429-433.
Gunda Gundo is located in the Tigray region, northern Ethiopia. It is a very remote area known for its monastery and
its sweet orange fruit. The oranges of Gunda Gundo have a unique flavor that is in demand by consumers. Despite the
superiority of the Gunda Gundo oranges in the local market, the quality attributes of these oranges is not studied and
compared to other orange breeds. This study was therefore initiated to analyze the fruit quality of Gunda Gundo
orange vis-a-vis other orange fruits in the region. Three different orange fruit varieties (Campbell Valencia, Olinda
Valencia, and Washington Navel) from Kola-Tembien and one variety (Hamlin) from Rama were used for
comparison with the Gunda Gundo orange. The fruits were harvested directly from the field, and for each variety
three trees were used as samples. Twelve orange fruits were sampled from each tree. For the Gunda Gundo fruit,
collection was made from upper, middle and lower sites across the gorge from both the Erob and Sa‟esi‟e side in three
different seasons (October 2012, December 2012, and January 2013). Then, the average of the three different months
was used for comparison with the other varieties. Because of the difference in ripening season, the orange varieties
from Kola-Tembien and Rama were collected in July 2012. The physical and biochemical fruit quality attributes: fruit
weight, peel thickness, fruit firmness, juice percentage, visual peel color, total soluble solids (TSS), and juice pH were
analyzed at Mekelle University laboratory. The analysis of variance revealed that there was a significant difference (P
< 0.05) among the varieties for all the quality attributes tested. Accordingly, the highest fruit weight was recorded in
Washington Navel. The highest firmness was recorded in Olinda Valencia. Peel thickness was similar among all
varieties except for Gunda Gundo orange which was the lowest of all varieties. Similarly, the lowest to TSS was
recorded in Washington Navel while it was similar in the other varieties. Juice percentage was highest in Gunda
Gundo and Olinda Valencia. The Juice pH was lowest in Olinda Valencia but other varieties had similar juice pH.
Taking TSS and pH as properties that is related to sweetness, Gunda Gundo, Hamlin, and Campbell Valencia oranges
are the sweetest fruits among the tested varieties. However, the juice percentage of Hamlin and Campbell Valencia
was significantly lower than Gunda Gundo fruit. Generally, taking the combination of TSS, pH, and juice percentage
as important fruit properties for consumer preference, Gunda Gundo oranges are superior as they were consistently
high in all of these properties unlike the other varieties which were high only in one or two of the three properties.
Key words: Orange fruit, Fruit quality, Variety, Total Soluble Solids (TSS), Juice pH
1
Department of Dryland Crop and Horticultural Sciences, Mekelle University, Mekelle, Ethiopia
Tigray Agricultural Research Institute, Mekelle Agricultural Research Center, Mekelle, Ethiopia
3
Tigray Agricultural Research Institute, Mekelle, Ethiopia
4
Department of Land Resource Management and Environmental Protection, Mekelle University, Mekelle, Ethiopia
*Corresponding author: e-mail - [email protected]
2
Received: January December 1, 2015; Accepted: May 9, 2016
INTRODUCTION
Citrus fruits are very important fruits, ranking first
with respect to fruit production in the world
(Ladanyia 2008). Even though citrus is a genius
that contains many important species, sweet orange
(Citrus sinensis) is the most important of all citrus
fruits in the world (Taylor 2008). Similarly, in 2013
orange was one of the important fruits in Ethiopia
with a total area coverage and total production of
3,000 ha and 36,000 tons respectively (FAO 2015).
Tigray region (Northern Ethiopia) is endowed with
diverse agro-ecology for the production of edible
wild and domesticated fruit species. However, the
production of fruits at a commercial level is
minimal, although there is a huge potential of
irrigable land that can be utilized for fruit
production (Ethiopian Investment Agency 2012).
The production of fruits and vegetables is also
expected to increase further because of the
attention given to nutrition security at national level
(NNP 2013). Currently, there is no detail
(published) information on the type of fruit
cultivars being produced in Tigray. Similarly, there
is minimal information on the total area covered
with fruits in the region. Nevertheless, citrus fruits
especially orange fruits are among the most
important fruits being produced in the region. It is
also one of the most important fruits in the local
markets. From our field visits to citrus orchards
around the region, we have found that different
orange varieties are being produced in Tigray.
These varieties include Campbell Valencia, Olinda
Valencia, Washington Navel, Hamlin and Gunda
Gundo orange. However, the production in the
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429
region is not enough and thus fruits from other
parts of the country also come into the local
market. Of all these available orange varieties,
however, the oranges of Gunda Gundo have a
unique quality that is in demand by consumers.
Gunda Gundo is located in the Tigray region,
northern Ethiopia. It is a very remote place known
for its monastery and its sweet orange fruits. Since
the variety of the orange fruits in Gunda Gundo is
not known, they are simply named by the name of
the place (i.e. they are called Gunda Gundo
orange). Confident with the fruit‟s superior quality,
supermarkets and other private dealers post
advertisements in a local language that says “Nay
Gunda Gundo Aranshi Alena” which is literally
translated as “we have Gunda Gundo orange” and
sell it with relatively higher price compared to
other orange varieties. Despite these merits, the
orange fruit of Gunda Gundo has not been studied.
Thus, the quality traits of these fruits are not
known. However, studying the quality of orange
fruit will have an important contribution in
pinpointing improvement strategies for other
orange varieties (Wismer et al 2005). This study
was, therefore, initiated to analyze the fruit quality
of Gunda Gundo orange vis-a-vis other orange
fruits in the region, and through comparison show
why it is preferred over the other oranges.
METHODOLOGY
Orange fruits from Gunda Gundo, Kola-Tembien
(Adiha) and Rama were collected for comparing
their fruit qualities. Gunda Gundo is located in
Eastern zone of Tigray. It is located at altitude of
1160- 1370 m.a.s.l and 14°22'01"N, 39°37'40"E.
average annual rainfall is 555mm and the
maximum and minimum temperatures are 34.5°C,
0
21.5 C respectively. The place has high and rugged
mountains; it is dominated by deep gorges, and
incised river valleys. The area has also historically
great value with old monastery. Adiha, which is
found in Central Tigray, is located between 13°
73'N and 39° 08'E at altitude of 1708 meter above
sea level and characterized by monomodal erratic
rainfall with annual average ranging from 436 –
700mm. Its maximum and minimum temperatures
are 27°C and 18°C, respectively. Its soil is
dominantly sandy, clay and loam. Rama is also
found in Central Tigray located at 14°409'38" N”
latitude and 38°735'45" E longitude. Altitude of
the study area ranges from 1300-1600 m.a.s.l. and
annual minimum and maximum rainfall ranges
from 400 to 700 mm respectively, The mean
maximum and minimum temperatures are 34°C
14°C respectively and the soil type is typically
sandy and loam.
The fruits of Rama and Kola-Tembien were
collected in July 2012. The Gunda Gundo orange
matures later, thus fruits were harvested in October
2012, December 2012, and January 2013. The
reason why we collected the Gunda Gundo oranges
at three different times is that they have an
extended maturity period. Moreover, in Gunda
Gundo, fruits were collected from upper, middle
and lower sites across the gorge from both the Erob
and Sa‟esi‟e side. This was because of the land
feature of Gunda Gundo which is sloppy unlike to
the other sites. Three trees were used as samples in
each site and 12 (4 small, 4 medium and 4 large)
oranges were collected and used as a composite
sample. Finally, the average of the three different
seasons was used for comparison with the other
varieties. Similarly, the oranges from KolaTembien (Adiha) were collected from three
different varieties (Campbell Valencia, Olinda
Valencia, and Washington Navel) whereas the
variety in Rama was Hamlin. Fruits were harvested
directly from the field and for each variety three
trees were used as samples. The number of oranges
taken from each tree is similar to that of Gunda
Gundo. The fruit quality was analyzed in Mekelle
University Laboratory. The fruit quality attributes
analyzed are listed below:
a. Physical Attributes
1. Fruit Weight: the weight of the individual fruits
in a sample was measured on digital
balance/weighing machine.
2. Peel Thickness: was measured with the help of
Vernier caliper according to Amador (2011).
3. Fruit Firmness: was measured using Effegi
penetrometer and was expressed as resistance to
puncturing the flesh of the fruit. It was done
according to Tabatabaekoloor (2012) with some
modifications. The average of puncture resistances
of two opposite sides of the fruit was taken and
expressed in kilogram force (kgf).
4. Juice weight: the total juice of each fruit was
collected into a beaker and weighed using digital
balance according to Zekri and Al-Jaleel (2004).
Finally, the juice weight was determined by
subtracting the weight of the beaker from the total
weight.
5. Juice Percentage: this is the percent by weight
of the juice to the weight of the fruit and was
determined by the following formula:
6. Visual peel color - peel color was scored
visually on four standard colors of citrus fruit rind,
according to IPGRI (1999) with modifications as
follows: yellow, light-yellow, green-yellow, and
green were given numerical values 1-4 respectively
(1 is yellow and 4 is green). The peel color of each
36 fruits from each variety was scored and the
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average was taken as the final color of that specific
variety.
b. Bio-chemical Attributes
1. Total Soluble Solids (TSS) - the TSS of the
orange juice which mainly contains sugars (Hui
2008) was determined using Digital Refractometer
according to Amador (2011). It was expressed as
degree Brix (°Bx).
2. Juice pH – this is a hydrogen-ion concentration
and provides an estimate of the extent of acidity in
the juice. It was measured with a pH meter
according to Cen et al (2006). Although the
common method to determine the acidity of an
orange juice is using titratable acidity (Zekri and
Al-Jaleel 2004; Fattahi et al 2011), the juice pH can
also be used as a measure of acidity (Cen et al
2006). Thus, juice pH was used to indicate the
acidity as titratable acidity was not determined
because of lack of equipments at the time of
analysis.
Figure 1. Fruit weight [Fruit WT (g)], Juice weight
per fruit [Juice WT/fruit (g)], and juice percentage
[juice % (W/W)] of the different orange varieties.
Means of each of the specified fruit attributes of the
different varieties which are not connected by the
same letter are significantly different from each
other at 5% significance level.
Data analysis
Data was analyzed using Microsoft excel and JMP
5. Significant differences between means were
determined using Tukey's HSD (honest significant
difference) test. In all cases the level of
significance used was 5 % (P < 0.05). Data are
presented as means ±SE (standard error of the
mean).
RESULTS
The analysis of variance has revealed that there was
a significant difference among the orange varieties
for all the attributes tested. The fruit weight of the
Washington Navel was significantly higher (P <
0.05) than the other varieties while the fruit weight
of the other varieties did not show any significant
difference among each other (Figure 1). Similarly,
the juice weight of Washington Navel fruit was
significantly the highest (P < 0.05) among the
varieties tested except for Olinda Valencia (Figure.
1). However, the juice percentage (W/W) was
significantly the highest (P < 0.05) in Gunda
Gunda fruits along with Olinda Valencia (Figure
1).
Gundo Gundo oranges were the least in peel
thickness among all the varieties except Olinda
Valencia (Figure 2). The highest flesh firmness was
recorded in Olinda Valencia while the lowest was
in Gunda Gundo orange (Figure 2).
Another physical fruit attribute (property)
tested was the fruit color. Accordingly, the color of
the fruit varieties varied from green to light-yellow
as indicated in (Table 1).
Figure 2. Fruit flesh firmness and peel thickness of
the different orange varieties. Means of each of the
specified fruit attributes of the different varieties
which are not connected by the same letter are
significantly different from each other at 5%
significance level.
*The fruit firmness of the variety Hamlin is not
included because of error in the procedure of
measurement.
Table 1. Visual peel color of different orange
varieties
Variety
Hamlin
Olinda Valencia
Gunda Gundo
Campbell Valencia
Washington Navel
Score
3.76
2.6
2.14
2.1
1.8
Color
Green
Green-yellow
Light-yellow
Light-yellow
Light-yellow
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Total soluble solids (TSS) and juice pH were
the biochemical fruit attributes examined.
Accordingly, significant difference (P < 0.05) in
TSS was observed between the highest values
which were recorded in Gunda Gundo and Hamlin
oranges and the lowest which was recorded in
Washington Navel (Figure 3). The juice pH was
significantly lowest (P < 0.05) in Olinda Valencia
but there was no any significant difference between
the pH of other varieties (Figure 3).
Figure 3. Total soluble solids [TSS in degree Brix
(°Bx))] and juice pH of the different orange
varieties. Means of each of the specified fruit
attributes of the different varieties which are not
connected by the same letter are significantly
different from each other at 5% significance level.
DISCUSSION
In the current study even though the highest TSS
values were recorded in Gundo Gundo and Hamlin,
they were not significantly different from the other
varieties except from Washington Navel (Figure 3).
Thus, the sugar content of Gundo Gundo, Hamlin,
Campbell Valencia, and Olinda Valencia fruits was
similar. However, the juice pH of Olinda Valencia
was significantly lower than the other varieties
(Figure. 3) indicating Olinda Valencia oranges
juice had the highest acid content. Opara et al
(2007) indicated that consumers give the highest
priority to flavor and sweetness when it comes to
valuing an orange fruit. The least important
attribute according to their finding was fruit size.
The total soluble solid content (TSS) and pH are
the two important attributes, among others, that
influence the consumers‟ preference towards
orange fruits (Cen et al 2006). The compositions of
total soluble solid of orange juice are mainly sugars
including fructose, sucrose and glucose (Hui 2008).
On the other hand, the pH of orange juice can be
used to show the acidity of the juice (Cen et al
2006). Thus, orange juice that has high TSS content
and high pH means it contains more sugars, and at
the same time is less acidic which indicates its
sweetness. Therefore, Considering the TSS and pH
properties, Gunda Gundo, Hamlin, and Campbell
Valencia oranges are the sweetest fruits among the
tested varieties. Similarly, the juice percentage
(W/W) of Gunda Gundo orange was the highest
among the tested fruits along with Olinda Valencia.
On the contrary, the juice percentages of Hamlin
and Campbell Valencia, varieties that had similar
TSS and pH with Gunda Gundo orange, were
significantly lower than Gundo Gundo oranges.
This additional property gives Gunda Gundo
orange superiority over Hamlin and Campbell
Valencia. It should be noted that the average juice
percentage of all the varieties ranged from 32.7 of
Hamlin to 48.88% of Gunda Gundo (Figure. 1).
Thus, with the exception of Hamlin all the other
fruits had juice percentage above the minimum
commercial standard set by UNECE (2012). The
minimum commercial standard according to
UNECE (2012) for the oranges other than blood
orange and Navels group is 35 while 33 is for
Navels group. There is no clear minimum market
standard for TSS content of orange fruits.
However, Hui (2008) have indicated that the TSS
of different orange fruits reportedly falls between 8
and 14 % with the minimum USDA (United States
Department of Agriculture) standard for processing
being 11.75 °Bx. In the current study, the TSS
varied from 9.35 in Washington Navel to 11.72 in
Gunda Gundo. Thus, the TSS of the tested varieties
is below the minimum USDA standard for
processing. However, it should be noted that the
TSS of Gunda Gundo oranges is only slightly lower
than that minimum standard. Nevertheless, this
indicates appropriate production practices such as
optimum plant spacing, pruning, proper watering
and fertilization might be lacking in orange
production in the region.
Other important fruit quality attributes such as
peel thickness and firmness were the lowest in
Gunda Gundo orange (Figure 2). Even though the
shelf life of the fruits was not investigated in the
current experiment, the peel thickness and fruit
firmness can have an implication on the shelf life
of the fruits, thus further study is needed to see the
shelf life. Zekri and Al-Jaleel (2004) have stated
that too high peel thickness is usually associated
with low fruit juice while too low peel thickness is
usually associated with post harvest problems.
Fruit color was another physical property that
was investigated in this study. However, according
to Machado et al (2015), fruit color may not
indicate the internal quality of orange fruits
especially when grown under tropical conditions.
Orange fruits grown in tropics can have an
excellent eating quality while they are still green.
Even though peel color of fruits may be an
important parameter for export market, local
consumers do not consider it as a priority in the
market (Machado et al 2015). This is also true in
the current study, as consumers prefer Gunda
Gundo orange to other fruits even though many of
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the other fruits tested had similar color to Gunda
Gundo orange.
CONCLUSION
Generally, each fruit variety has shown superiority
over others in some of the fruit properties tested.
However, taking the combination of TSS, pH, and
juice percentage as important fruit properties for
consumer preference, Gunda Gundo oranges take
the highest rank as they were consistently high in
all of these properties unlike the other varieties
which were high only in one or two of the three
properties. However, Gunda Gundo oranges were
inferior in terms of fruit weight which was the
highest in Washington Navel oranges. The fruit
firmness and peel thickness were also the lowest in
the Gunda Gundo orange while Olinda Valencia
fruits were superior in fruit firmness. Thus, the
variabilities shown among the orange varieties can
indicate the genetic diversity which can be utilized
for further improvement through plant breeding. As
a limitation of this study, it should be noted that the
difference in the fruit quality attributes between
Gunda Gundo orange fruits and the others might or
might not be because of the varietal differences. As
these fruits were grown in different locations,
differences might also be caused by environmental
factors. Moreover, the age of the sampled fruit trees
was not clearly determined which might also cause
unintended differences. To clearly identify the
source of the difference it is mandatory to grow
them in similar locations.
ACKNOWLEDGEMENTS
This research was funded by the recurrent budget
of Mekelle University. We would also like to thank
Tigray Agricultural Research Center (TARI) and
Relief Society of Tigray (REST) for their
administration support.
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