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Agr. Nat. Resour. 56 (2022) 113–120
AGRICULTURE AND
NATURAL RESOURCES
Journal homepage: http://anres.kasetsart.org
Research article
Durian volume determination using short-range coded-light three-
dimensional scanner
Thana Cheepsomsonga,†,*, Jingtair Siriphanichb,†
a
Department of Mechanical Engineering, Faculty of Engineering at Khamphaeng Saen, Kasetsart University Khamphaeng Saen
Campus, Nakhon Pathom 73140, Thailand
b
Department of Horticulture, Faculty of Agriculture at Khamphaeng Saen, Kasetsart University Khamphaeng Saen Campus,
Nakhon Pathom 73140, Thailand
Article Info Abstract
Article history: Importance of the work: The quality of a durian fruit can be inferred from its specific
Received 11 November 2021
gravity, whose determination requires its volume. Traditionally, the volume of a durian is
Revised 30 December 2021
Accepted 12 January 2022 determined by the water displacement method; However, this is a slow process that runs
Available online 25 February 2022 the risk of fungal growth due to residual high humidity.
Objectives: The present study evaluated the viability of three-dimensional (3D) scanning
Keywords:
as an alternative approach to water displacement for the determination of the volume of
Durian,
Maturity, durian fruit.
Specific gravity, Materials & Methods: Durian fruit samples at different maturity levels and harvested
Three-dimensional (3D) scanning,
from two different growing areas were determined for volume using the traditional
Volume
specific gravity method and compared with volumes measured using the 3D scanning
method. Each scan took about 60 s.
Results: The analysis showed that there was no significant (p > 0.05) difference between
the traditional and proposed methods for durian fruit of different maturity levels. The
average relative percentage difference was 1.06% (sample size of 116), which was less
than that obtained from other reported studies that tested other fruits with reasonable axial
symmetry.
Main finding: The proposed alternative technique has potential for the continuous and
automatic measurement of the volumes of durian fruit on a moving conveyor belt, as a
part of the maturity determination process.
† Equal contribution.
* Corresponding author.
E-mail address: thana.c@ku.ac.th (T. Cheepsomsong)
online 2452-316X print 2468-1458/Copyright © 2021. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/),
production and hosting by Kasetsart University of Research and Development Institute on behalf of Kasetsart University.
https://doi.org/10.34044/j.anres.2021.56.1.11
114 T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120
is likely to be adequately mature; if it subjectively feels too
Introduction heavy, the durian is too young (Siriphanich, 2011).
Finding the specific gravity of a fruit requires its volume,
Durian is an important export fruit mainly from eastern which is usually measured by the slow and cumbersome water
and southern of Thailand, with broad consumer approval displacement method; having been subjected to this method,
internationally for its quality and taste (Gasik, 2017). In each durian must be dried to prevent fungal growth (Piasai
2019, Thailand exported 655,394 t of fresh durians, valued et al., 2021). Alternative approaches have been devised to
at USD 1,421million (Office of Agricultural Economics, measure the volumes of agricultural products. Mutschler et
2021). However, durian exporters may unintentionally export al. (1986) estimated the volume of a tomato by measuring
immature durians, damaging the export market. The problem its height and width, with a correlation coefficient (r) of
arises from failing to select adequately mature durians for 0.99 compared with the actual volume. Yuan and Sun (1995)
harvest, which requires experience and high skill. With suitable developed a formula to estimate the volume of an apple from
equipment, maturity sorting could be more accurate. its height and width to within 1.86% of the actual volume.
Durian farmers rely on the following techniques to In Japan, the density of a watermelon is related to its
determine if a durian is mature: tracking the time elapsed from mushiness and sweetness; however, calculating the density
flowering; testing if two spines are less resistant to pinching; requires knowing the volume and this measurement
examining if the carpel lines are more dilated; and checking is inconvenient and time-consuming (Kato, 1997). Kato
if the sound pitch has a hollow resonation when the durian (1997) developed an instrument to measure the volume of a
is tapped (Bureau of Plant Industry, 2019). These techniques watermelon based on its electrical property. The instrument
are time-consuming and tend to tire the sorters. An alternative has a hexagonal tunnel whose walls constitute an electrode,
option is desirable based on some maturity index that can with the watermelon holder in the tunnel being the other
distinguish between immature and mature durians. Currently, electrode. The instrument measures the capacitance between
the pulp dry matter is used as an official standard for durian, the watermelon surface and the tunnel walls. The capacitance
but this requires destructive testing (Sangwanangkul and was related to the volume of the watermelon (R2 = 0.92).
Siriphanich, 2000). Another technique for measuring the volume of a fruit is
The specific gravity of a durian is related to its quality, with based on determining the volume of empty space around a
Haryanto and Budiastra (1999) reporting that riper Indonesian fruit in its container. One instrument for such a technique is a
durians had lower values of specific gravity. Another study on ring system that has infrared emitters and sensors around the
Monthong durians produced similar findings (Youryon et al., inner side (Gall et al., 1998). Without a fruit inside the ring,
2017). In a follow-up study, Haryanto and Budiastra (2000) each sensor detects light from the opposite emitter. With a fruit
showed that the specific gravity of a Sunan durian was related inside, only some of the sensors detect light. The resulting
to its density and sweetness, with coefficients of determination signals are converted into the area of the empty space around
(R2) of 0.89 and 0.88, respectively. The specific gravity of a the fruit, which when subtracted from the area inside the ring
Monthong durian is always less than one, and decreases as gives the area of that particular cross-section of the fruit.
the durian becomes more mature, whereas the initial specific Repeating this for successive cross sections allows the volume
gravity of a ripening Monthong durian is 0.95, decreasing to be calculated. Testing this method on potatoes produced an
to 0.90 when the durian is fully ripe (Siriphanich, 2011). accuracy greater than 95%, where the accuracy depended on
Yantarasri (2002) made a prototype sorting machine based the number of sensors and the size of the ring (Gall et al., 1998).
on durian maturity by floating the durian in a tank filled with Nishizu et al. (2001) developed an instrument to measure
water, the density of which was controlled and adjusted by the volumes of agricultural products on a running conveyor
injecting small bubbles into the water. The sorting efficiency belt. The instrument consisted of a Helmholtz resonator, which
was reported to be up to 100% for sorting a mature durian from is a spherical chamber with an open neck at the top. When
an immature durian. Specific gravity has come to be accepted as an object is placed inside the chamber and air is blown over
one of the maturity indices for Monthong durians (Siriphanich, the opening, the instrument vibrates at a natural frequency
2011). In addition, durian farmers can assess Monthong durian depending on the volume of the object. The sound signals are
maturity by gauging its weight when lifted by the peduncle. If measured using a microphone and analyzed for the natural
the fruit feels too light based on its apparent volume, the durian frequency, from which the volume of an agricultural product
T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120 115
placed inside the chamber can be calculated. They found that with a computer software package 3D Systems Sense™
the natural frequency was related to the volume (R2 = 0.97). Version 3.0.213 (Rock Hill, SC, USA). The 3D scanner was
Another technique for measuring the volume of a non- connected to a computer via a USB 3.0 port. The computer was
spherical fruit, such as a cantaloupe, combined image processing equipped with an Intel i7-8770K processor with 8 GB of RAM
with the disk approximation method (Rashidi et al., 2009). and an Nvidia Quadro 2000 video card. To prepare for the scan,
There was no significant difference (at the 95% confidence a durian was hung vertically, as shown in Fig. 2. The scan was
level) between the technique and the water displacement carried out by manually moving the scanner along six paths
method. Costa et al. (2016) took a photograph of a palm around the stationary durian. As shown in Fig. 3, scanning a
fruit and used the Moire technique to determine its volume. durian started at point A and proceeded along path 1 toward
Compared to the water displacement method, the r value point B, then along path 2 back to point A. The procedure was
was 0.65. Concha-Meyer et al. (2018) used a machine vision repeated along paths 3–6. Each scan took about 60–90 s per
technique to determine the volumes of tomatoes, mushrooms durian, depending on the durian shape.
and strawberries from their photographs. Compared to the The 3D image file had an STL (Standard Triangle Language,
water displacement method, the values of R2 ranged from 0.92 invented by Grimm, 2004) extension. Fig. 4 shows a 3D image
for mushrooms to 0.99 for tomatoes. Villordon et al. (2020) from the file compared to the fruit photo. The volume was
used a three-dimensional (3D) scanner to determine the volume calculated based on the STL file, as described in the next part.
of sweet potato. The 3D scanned volume was highly correlated
(R2 = 0.81) with the volume based on water displacement.
A three-dimensional (3D) scanner provides a non-
destructive means for volume measurement. However, the
technique has only been applied to agricultural produce with a
smooth surface. The present study investigated the application
of a 3D scanning technique in conjunction with computer
software to determine the volume of a durian whose shape is
complex and spiky.
Materials and Methods
Durian samples Fig. 1 Sense-RS, short-range coded-light three-dimensional scanner
Fruit samples of 42 and 78 Monthong durians from Rayong
province (12°53'27.6"N 101°37'08.4"E) harvested in September
2021 and Yala province (6°15'25.2"N 101°24'25.2"E) harvested
in October 2021, respectively, were obtained from packing
houses and manually sorted by tapping sound into four
groups of approximately the same maturity: immature, almost
mature, mature and overly mature. The sorting was carried out
manually by commercial sorters. The weights of each durian
were in the range 2.185–5.655 kg for the Rayong durians and
1.610–6.385 kg for the Yala durians.
Method
Building a 3D model of a durian from its 3D scan
A short-range coded-light 3D scanner, Sense-RS (Rock
Hill, SC, USA), as shown in Fig. 1, was used in conjunction Fig. 2 Durian hanging in position for three-dimensional scanning
116 T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120
the STL volume using Equation 1:
Scanned volume=Correction factor × STL volume (1)
When a test cylinder was scanned using the equipment in
the present study, its actual volume was smaller than the STL
volume by a factor of 0.92; therefore, this was used as the
correction factor in Equation 1.
Durian volume measurement using water displacement
method
The volume of a durian obtained from the water displacement
method is hereinafter referred to as its reference volume. The
Fig. 3 Diagram showing scanning process: A→1→B→2→A→3→ water displacement method is a basic method for volume
B→4→A→5→B→6→A determination (Mohsenin, 1986). The temperature of water
used in each measurement was 25 ± 1°C. The measurement of
the reference volume of a durian commenced by weighing the
container filled with water (measured in kilograms). Next, the
durian was immersed in the water so that only the peduncle was
not submerged. The new weight was recorded.
The reference volume (measured in liters) was defined as
the volume of the water displaced by the durian, calculated
using Equation 2, with the weight of the water displaced by a
durian (measured in kilograms) calculated using Equation 3.
Reference volume = Weight of water displaced
by durian / Water density (2)
Fig. 4 (A) Actual photo of durian sample; (B) Corresponding three-
dimensional model constructed using 3D scanner where the density of water was assumed to be 0.997 kg/L
at standard temperature and pressure (25°C and 101.325 kPa).
Durian volume calculation from STL file For example, if the displaced water weighed 997 g, then its
Calculating the volume of a durian from its STL file volume would be 1 L.
(hereinafter referred to as the STL volume) used the Python 3.8
software (Python Software Foundation; https://www.python. Weight of water displaced by durian =
org) and a library called numpy-stl containing the function get_ Weight of system with durian immersed -
mass_properties that was used in the calculation, based on a Weight of system without durian (3)
technique making use of polyhedral mass properties developed
by Eberly (2002) for the determination of the volume of a solid Statistical analysis
3D object.
Scanned volumes and reference volumes were subjected to
STL volume correction regression analysis to determine the coefficient of determination
The STL volume required correction using a factor that (R 2) for the derived model. The accuracy of the scanned
was determined based on the STL volume of a simple cylinder volumes was based on the standard error of estimate (SEE),
whose actual volume was easily determined. The correction given by Equation 4 (Smith, 2015):
factor was defined as the ratio between the actual volume and
the STL volume. The corrected volume (hereinafter referred to (4)
as the scanned volume) of any object could then be related to
T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120 117
where Sy,x is the standard error of the estimate, y is the greatest differences between the 3D scanned and reference
reference volume, yest is the scanned volume and n is the sample volumes were all irregularly shaped with some of their lobes
size. Differences between the scanned and reference volumes oddly twisted, as shown in Fig. 5C, making them unfit for
of the durian samples were considered significant at the 95% export. The poor results were generally because irregular
confidence interval level based on a paired sample t test, using surface furrows were obscured by crowded spikes (as shown in
Microsoft Excel (Microsoft Corporation; Redmond, WA, Fig. 5C). However, this did not affect the utility of the present
USA). Values were presented as the mean ± SD. method in practice, because durian volumes are determined
only for durians with a regular shape that can be exported.
Once the misshapen durians had been discarded from the
Results and Discussion analysis, there was still no significant difference between the
scanned and reference volumes (p = 0.292).
Volume All 78 Yala durians were regularly shaped and suitable for
export. Their t test analysis revealed there was no significant
The volumes of the durian samples in the present study are difference between the reference and scanned volumes (p =
shown in Table 1. The mean reference volumes were 4.069 ± 0.653, Table 2). The volume difference was even lower than
0.915 L and 3.531 ± 1.128 L, for the Rayong and Yala durians, for the Rayong durians based on the higher p value for the Yala
respectively. The mean scanned volumes were 4.087 ± 0.910 sample, probably due to the greater number of regular-shaped
L and 3.452 ± 1.060 L for the Rayong and Yala durians, samples.
respectively. Thus, the durian samples from Yala had a broader All samples from the two provinces were combined and re-
volume range than those from Rayong because of their wider analyzed using the t test. The scanned volume of the combined
range in mass, not shape, as the durians from both regions were durians from both provinces was not significantly different
the same cultivar. from the reference volume (p = 0.738, Table 2).
For the regular-shaped durians, the present study recorded
Results from statistical analyses better volume measurement agreement than was reported for
the image analysis by Rashidi et al. (2009), whose cantaloupe
Analysis using t test volume determination had a p-value of 0.207 in the paired
For the 42 Rayong durians, the statistical analysis based sample t test. They determined the volume of an axially
on the paired t test between the scanned volume and reference symmetric cantaloupe based on a combination of 2D image
volume was not significant (p = 0.117), as shown in Table 2.
Further inspection of the samples revealed that four durians had
unusually high discrepancies between the reference volume
and scanned volume, probably because they were misshapen,
whereas the others were more regularly shaped. Regular-
shaped durians can be evaluated for symmetry once pollination
and fertilization are complete (Siriphanich, 2011), with a
symmetrical fruit having even carpels all around, as shown
in Fig. 5A. If there is incomplete pollination and fertilization,
some carpels are smaller and the durians are considered to be Fig. 5 (A) Regular-shaped, symmetrical durian; (B) Regular-shaped but
asymmetrical, as shown in Fig. 5B. The four durians, with the asymmetrical durian; (C) Misshapen durian unfit for export
Table 1 Descriptive statistics of durian volumes (in liters) for 38 durians from Rayong and 78 durians for Yala
Province Volume category Minimum Mean Maximum SD
Rayong Reference volume 2.445 4.069 6.515 0.915
Rayong Scanned volume 2.444 4.087 6.560 0.910
Yala Reference volume 1.585 3.531 6.270 1.128
Yala Scanned volume 1.637 3.452 5.973 1.060
118 T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120
analysis and longitudinal dissections. In the present study, the on photography in conjunction with the so-called Moire
average relative percentage difference between the reference technique. That approach produced an R2 value of 0.837 and an
and scanned volumes based on the combined samples using average relative percentage difference of 11.09%, with respect
only the regular-shaped fruit from the two provinces was to the volume obtained using the water displacement method.
1.06%, whereas that in the cantaloupe study was 7.60% Concha-Meyer et al. (2018) determined the volumes of
(Rashidi et al., 2009). tomatoes using a technique similar to that of the present study.
They took photographs of multiple sides of each tomato while
Regression analysis it was rotated 6° at a time, resulting in 30 photos per tomato.
Table 3 shows the results of the regression analysis These data were analyzed and converted to volumes using
comparing the durians from the two provinces. The equation the OmniSurface software (Smart Vision Works International
resulting from the regression analysis is shown in Equation 4: LLC; American Fork, UT, USA). The technique produced an
average relative percentage difference of 2.18%, which was
Reference volume = (a + b) × Scanned volume (4) less accurate than that of the present study (1.06%). However,
the discrepancy was understandable for three reasons. First,
where a is the intercept value and b is the regression their scanner and 3D reconstruction software were different.
coefficient.
For the Rayong durians, the equation had an R2 value 0.948
(Table 3) for all 42 durians and an R2 value of 0.987 when the
misshapen durians were excluded. For the Yala durians, the R2
value was 0.996, which was consistent with the results from
the t test analysis. For the combined regular-shaped samples
from the two provinces, the regression analysis had an R2 value
of 0.991. The SEE of the combined analysis was 0.106, which
was better than for the Rayong analysis. The relationship as
revealed by regression analysis between the reference volume
and the scanned volume based on the combined samples is
shown in Fig. 6.
The R2 value (0.991) of the spiky-surfaced durian in the
present study was higher than for smooth-surfaced sweet potato
(R2 = 0.81) that was also based on 3D scanning (Villordon Fig. 6 Regression of three-dimensional (3D) scan volumes on volumes
et al., 2020). Costa et al. (2016) determined the volumes from water displacement method based on combined samples from two
of palm fruits, whose shapes are fairly symmetrical, based provinces
Table 2 Results from paired t test between the scanned and reference volumes of durian fruit
Province Sample Quantity p-value
Rayong Full 42 0.117
Rayong Excluding misshapen durians 38 0.292
Yala Full 78 0.653
Rayong and Yala Only regular-shaped samples 116 0.738
Table 3 Results from regression analysis to predict durian volume based on scanned volume
Province Sample Coefficient of determination Standard error of estimate p-value
Rayong All samples 0.948 0.222 7×10-28
Rayong Excluding misshapen durians 0.987 0.107 2×10-35
Yala All samples 0.996 0.072 7×10-92
Rayong and Yala Only regular-shaped samples 0.991 0.106 1×10-117T. Cheepsomsong, J. Siriphanich / Agr. Nat. Resour. 56 (2022) 112–120 119
Second, the distance between the scanner and object in their
setup was different (0.3 m in the present study versus 1 m for Conflict of Interest
theirs). Third, durians are much bigger than sweet potatoes, and
therefore give better resolution. The authors declare that there are no conflicts of interest.
The present study showed that although a durian was
asymmetrically shaped with a non-smooth surface, its scanned
volume was close to its reference value. The estimated volume Acknowledgements
based on the 3D scan was better than achieved in other studies
of agricultural materials whose shapes were reasonably A s s o c . P r o f . D r A n u p a n Te r d w o n g w o r a k u l o f
symmetrical and smooth. The technique in the present study the Department of Agricultural Engineering, Faculty of
could be adapted for use with a LiDAR 3D scanner, whose Engineering, Kamphaeng Saen Campus provided helpful
speed and resolution are higher than the system used in suggestions and advice on planning the experiment, without
the present study, in conjunction with custom software for which the experiments would not have proceeded as smoothly.
volume determination. In addition, the technique could be The Agricultural Research Development Agency (Public
further developed for the continuous measurement on a Organization) provided the durian fruit for research purposes.
moving conveyor belt. Furthermore, the technique could be The Kasetsart University Research and Development Institute
incorporated as part of more complicated processes. For (KURDI), Bangkok, Thailand provided assistance with English
example, combining it with a system that can measure the editing.
weight would then allow the specific gravity to be determined.
In addition, the system could also use multiple scanners from
different angles simultaneously. Finally, the system could References
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