Evaluation of Tomato Fruit Color Change with Different Maturity Stages and
Storage Temperatures Using Image Analysis
Noriko Takahashi, Honami Maki, Hiroshige Nishina, Kotaro Takayama

Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566
Japan (Tel: +81-89-946-9761; e-mail: takahashi.noriko.mm@ehime-u-ac.jp).
Abstract: The effects of storage duration and temperature on the tomato fruit color change and quality
with different maturity stages tomato were investigated in this study. Tomatoes were grown
hydroponically in high technology greenhouse. Tomato fruit samples with green to red were stored in
cool incubator for 48 h. The storage temperature was adjusted at 15 C and 20 C. The maturity stage of
tomato fruit was evaluated with chiromaticity by image analysis. Little tomato fruit color change with
storage was observed in large maturity stage (red fruit) regardless of storage temperature. Chromaticity in
small maturity stage (green fruit) was increased with storage time. The sugar content of fruit was
increased and fruit firmness was decreased with storage at both temperatures for 15 C and 20 C
regardless of maturity stage.
Keywords: Greenhouse, Image analysis, Maturity, Storage temperature, Tomato.

1. INTRODUCTION
In high technology greenhouse, the stable plant production
is required for customers. For tomato production in
greenhouse, tomato fruit color is the most important
marketing factor that is often used for the purchase decision
of customer. Since tomato fruit color is varied with the
harvesting time and the ripening in tomato fruit is affected by
storage temperature (Takahashi and Nakayama, 1962), it is
difficult to achieve an even tomato color at the shipping time.
Therefore, storage temperature control depended on the
maturity stage of tomato fruit is essential for stable tomato
production in high technology greenhouse. However, it is
unknown that the tomato color change with different maturity
stages and storage duration and temperatures.
The maturity stage of tomato fruit was classified with the
chromometer (Maezawa et al., 1993; Batu, 2004; Lopez
Camelo and Gomez, 2004), or image analysis (Motonaga et
al., 1987; Choi et al., 1995). The objective of this research
was to investigate the effects of storage duration and
temperature on the tomato fruit color change and quality with
different maturity stages tomato using image analysis.
temperature was adjusted at 15 C and 20 C. Relative
humidity was 80  10 %. Tomato fruit image and quality
measurement were conducted at the harvesting time (0 h) and
24 h and 48 h after storage.
Fig. 1 shows the flow chart of tomato fruit color calculation.
Tomato fruit image was captured with Digital Camera (SX5WKIT, Canon Inc.), as shown in Fig. 2. The measurement
distance was 115mm from the top of the tomato fruit. The
camera condition was adjusted with F value, shutter speed,
and ISO for 5.0, 1/30, and 200, respectively. A ring-shaped
white LED was used for light source. The light intensity was
adjusted for 2500 lx at the top of the tomato fruit. The
polarizing filter (C-PL 58, Kenko Co., Ltd.) and film (45669L, Edmund Optics Co. Ltd.) were equipped with camera and
light source to reduce halation from surface reflectance of
tomato fruit. After capturing image, the image was processed
with application which was programmed with Visual basic
(Microsoft Visual Studio 2010). The fruit area was extracted
with discriminant analysis method. RGB values were
obtained from the fruit image and the color characteristics
were calculated according to Kurita et al. (2006). In this
study, chromaticity was used for maturity evaluation of
tomato fruit. Chromaticity (C) was given by
2. MATERIALS AND METHODS
Tomatoes (Lycopersicon esculentum Mill. ‘Momotaro
Sakura’) were grown hydroponically in high technology
greenhouse in Faculty of Agriculture, Ehime University.
Tomato seeds were sown on August 18 and transplanted on
September 20 in 2011. The harvesting time was June 25 and
27 in 2012. Each harvesting time, different maturity stages of
tomato fruits with green, pink, and red colors were obtained.
Then these tomato fruits were visually classified from 1
(green) to 10 (red). Six tomato fruits were stored in cool
incubator (A1201, Ikuta Sangyo) for 48 h and the storage
C 

iM
color ( i ) 
color (i )
S
rg
 255
r g b
(1)
(2)
where S is tomato fruit area, M is total pixel of tomato fruit,
and r, g, and b are brightness value of R, G, and B.
As conventional method, tomato fruit color was also
measured using a chromometer (CR 200, Konica Minolta
Fig. 4 shows the results of effects of storage duration and
temperature on tomato fruit color change with different
maturity stages. Little tomato fruit color change with storage
was observed in large maturity stage (red fruit) regardless of
storage temperatures. Chromaticity in small maturity stage
(green fruit) was increased with storage time. The increase in
chromaticity with storage at 20 C was larger than that with
storage at 15 C. These results suggest that tomato fruit color
change with storage is different from the maturity stage of
tomato fruit, especially the tomato color change in green fruit
is more sensitive to storage duration and temperature
compared with that in red fruit.
Tomato fruit image
acquisition
2.5
150
Chromaticity
Color information
acquisition of fruit area
2.0
a*/b*
90
1.5
60
1.0
30
0.5
0.0
0
1
Chromaticity calculation
Fig. 1. Flow chart of tomato fruit color calculation.
4
6
8
10
Visual maturity evaluation
Fig. 3. Comparison on maturity evaluation of tomato fruit
between visual evaluation and chromaticity from the image
and a*/b* with chromometer. The coefficient of
determination (R2) was 0.997 for chromaticity and 0.975 for
a*/b*, respectively.
10-15℃
10-20℃
155
Ring-shaped
white LED
9-15℃
7-20℃
4-15℃
2-20℃
11
Chromaticity
115
9
95
7
75
5
55
3
35
1
15
0
3. RESULTS AND DISCUSSION
The maturity stage evaluation of tomato fruit was
compared between visual evaluation and chromaticity from
the image and a*/b* with chromometer, as shown in Fig. 3.
The coefficient of determination for chromaticity was higher
than that for a*/b*. This result suggests that maturity stage of
tomato fruit can be evaluated with chiromaticity by image
analysis.
1-15℃
1-20℃
13
135
115mm
Fig. 2. Tomato fruit color measurement system.
a*/b*
Fruit area extraction with
discriminant analysis method
Chromaticity
120
Visual maturity evaluation
Optics, Inc.) at top and side of tomato fruit and a*/b* was
calculated for the maturity stage evaluation.
For quality measurement, sugar content, firmness, and fresh
weight of tomato fruit were examined. The sugar content of
fruit was measured non-destructively with grading machine
(SSW-1APQ-6R, Iseki & Co., Ltd.) which was calibrated
with Refractometer (RF113, Tensho). The fruit firmness was
determined by a firmness meter (KM-5, Fujiwara Scientific
Company Co., Ltd.). The fresh weight of tomato fruit was
measured with scale (EK-300i, A&D Co. Ltd.) and fresh
weight decrease rate was determined with the weight from
before and after storage.
24
Time (h)
48
Fig. 4. Effects of storage duration and temperature on
chromaticity of tomato fruit with different maturity stages
(Symbol caption represents “maturity stage - storage
temperature”). Storage temperature was adjusted for 15 C
and 20 C.
Table 1. Effects of storage duration and temperature on sugar content, firmness, and fresh weight decrease rate (FWDR) of
tomato fruit with different maturity stages. Storage temperature was adjusted for 15 C and 20 C. Data represents means 
S.D. (n=4).
Storage
temperature
(C)
15
20
Maturity
stage
1-5
6-10
1-5
6-10
Before storage (0 h)
Sugar
Firmness
content
(kg)
(Brix%)
4.10  0.23
0.66  0.14
4.16  0.34
0.53  0.09
4.24  0.47
0.88  0.06
4.06  0.23
0.63  0.10
24 h after storage
Sugar
Firmness
content
(kg)
(Brix%)
0.59  0.03
4.78  0.38
0.42  0.09
4.89  0.25
0.70  0.04
4.57  0.44
0.44  0.09
4.51  0.44
The effects of storage duration and temperature on sugar
content, firmness, and fresh weight decrease weight of
tomato fruit with different maturity stages were examined
(Table 1). The sugar content of tomato fruit was increased
and fruit firmness was decreased with storage at both
temperatures for 15 C and 20 C regardless of maturity
stages.
The fresh weight decrease rate with storage at 20 C was
larger than that with storage at 15 C regardless of maturity
stage. These results suggest that there is no effect of maturity
stage on fruit sugar content, firmness, and fresh weight
change with storage. More various maturity stages of samples
and storage temperatures might be considered for further
study.
4. CONCLUDING REMARKS
Effects of storage duration and temperature on the tomato
fruit color change and quality with different maturity stages
tomato was investigated using image analysis. Our results
showed that tomato fruit color change with storage was
varied depending on the maturity stage of fruit. No difference
in fruit sugar content, firmness, and fresh weight change with
storage was observed among the maturity stage.
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FWDR
(%)
0.25
0.19
0.33
0.36
48 h after storage
Sugar
Firmness
content
(kg)
(Brix%)
4.72  0.24
0.49  0.10
4.91  0.28
0.33  0.04
4.45  0.42
0.65  0.00
4.61  0.64
0.42  0.04
FWDR
(%)
0.55
0.49
0.68
0.70
Takahashi, T. and Nakayama, M. (1962). Studies on the
coloration of tomato fruits. VIII. Effect of storage
temperature on pigment contents of fruits. Journal of
Japanese Society of Horticultural Science, 31, 33-36.