Internal Quality Analysis of Watermelons by an Acoustic ... - ACIAR

Internal Quality Analysis of Watermelons by an Acoustic
Technique and Its Application in Japan
Yoshihide Kouno*, Toshihiro Mizuno*, Hiromu Maeda*,
Takayoshi Akinagat, and Y oshihiro Kohdat
WATERMELON is now generally sold in cut sections in
supennarkets and retail stores in Japan. Therefore, it has
become necessary to detect and sort out hollow and
overripe fruit, and mcans of doing this have become a
major focus of attention in the production area in setting
new shipping standards. Usually, watcrmelons have
been tested for ripeness by skilled inspectors who slap
the surface of the watermelon and judge the ripeness by
relying on factors such as the pitch and tone of the sound
produced. With this method, however, many years of
experience are required before any degree of precision
can be expected in classification of watennelons. As the
number of skilled inspectors decreases due to ageing,
there has been a strong call for the development of
automatic quality measuring and sorting devices.
Various rcsearehers have investigated nondestructive
measurement of the internal quality of
watennelons (Chuma 1977; Yamamoto 1984; Sasao
1985; Kawamura 1(88). Howcver. there are no practically
applicable on-line mcasuring and sorting devices
which can assess ripeness and at the sallle time determine
whether or not a watermelon is hollow. We studied
a method of classifying ripeness and detecting hollow
watennelons using an acoustic techniquc, and this
research led to the development of the MW A-9002
system for sorting watermelons.
Components and Principles
Measurement of ripeness and detection of hollow
watermelons
The system, which measures ripeness and detects
hollow watermelons, consists of a mechanical supply
section. a height measurement section, an acoustic
sound measurement section. a display section, and a
wave analysing device (Fig. I). With the acoustic technique,
the watennclon is slapped with a small hammer,
and ripeness and presence of hollows arc detected based
* Fantec Institute Co. Ltu. (LV) Sasagasl'. Hamamatsu. Shizuoka,
435. Japan.
t Department of Bioproullction, College of Agriculture, University
of the Ryukyus, I Senbaru, Nishihara. Okinawa,
903-0 I. Japan.
382
on changes in the sound waves transmitted from the
interior of the waternlelon.
Measurements of ripeness and hollowness of the
melon are made by Fast Fourier Transform (FFf) analysis
of the waveshape of the sound. The results from a
nonnal and a hollow watermelon using this device are
shown in Figures 2 and 3, respectively, Comparing the
original wave and the auto correlation coefficient wave
from a norillal melon with those from a hollow melon
shows that a nonnal melon produces a clean damped
waveshape, while a hollow melon produces a disordered
waveshape, Thus, to determine whether a melon is
hollow. the sum of the peak waveshape for given cycle
is determined, and the result is compared with a judgment
value established in advance. If the watennelon is
normal, the peak frequency of the power spectrum is
clearly damped, but if the melon is hollow, there will bc
more than one peak, with the second peak tending to
have a lower frequency than the first.
The quality of the melon can be detennined by comparing
the difference between the peak frequencies with
the judgment value. Hollow spots and cracks, however,
appear not in one isolated spot, but in a variety of locations.
Consequently, there arc cases in which these tlaws
cannot be detected using a sensor. As a result of our
research, we realised that a minimum of three sensors is
necessary for accurate measurement. There is a strong
correlation between the ripeness of a watennelon and
the hardness of its fruit. It has been reported that the peak
frequencies gradually shift from higher frequencies to
lower according to the ripeness. The transition speed
varies considerably depending on the size of the melon.
Therefore. we have found that it is not possible to accurately
measure ripeness simply by determining the peak
frequency. The relationship between the peak frequencies
was studied in terms of fruit size and changes in
ripeness, We found. when measuring ripeness, that it
was necessary to correct for the diameter of the melon
when measuring the peak frequency of power spectrum
detennined through wave analysis (sec Fig. 4).
Capacity of the sorting system
This equipment is capable of processing 3600 watermelons
per hour. The tlow of the sorting process is as

quality. This system has been installed in nine locations
throughout Japan where watermelons are being sorted
and packed automatically.
References
Chuma. Y .. Shiga. T. and Hikida. Y. 1977. Vibrational and
impact response properties of agricultural products for nondestructive
evaluation of internal quality (Part I). Joumal of
the Japanese Society of Agricultural Machinery. 39(3).
335-341.(in Japanese)
384
Kawamura. T. and Nishimura. I. 1988. Studies on the physical
property of watermelon (Part I). Joumal of the Japanese
Society of Agricultural Machinery. 50(2). 85-92. (in Japanese)
Sasao, A. 1985. Impact response properties of watermelons in
growth process. Journal of the Japanese Society of Agricultural
Machinery, 47(3). 355-358. (in Japanese)
Yamamoto, H. and Haginuma. S. 1984. Dynamic viscoelastic
properties and acoustic properties of watermelons. Report of
National Food Research Institute, 44. 30 -35.

Feasibility Studies into NIR Technique for Measurement of
Internal Quality of Some Tropical Fruits
Yoshihide Kouno*, Toshihiro Mizuno*, Hiromu Maeda*, Takayoshi Akinagat,
Tetsuya Tanabet, and Y oshihiro Kohdat
UNTIL recently, most pineapples grown in Okinawa
Prefecture have been used for processing. Crops reached
a peak during the period 1965-1970, but since then the
size of the crop has declined. In 1988, the crop fell to less
than half of the 35 500 tons obtained during peak times.
Furthermore, the 1988 GAIT decision to liberalise
imports of canned pineapple, beginning in 1990, dealt a
severe blow to the Okinawa Prefecture pineapple industry
(Kohda 1990; ODA 1990; OPG 1990). Since Okinawa
Prefecture has a geographical advantage which
allows companies to transport pineapples faster and with
less deterioration than other suppliers, Okinawan famlers
have been expanding into the market for fresh pineapple.
However, when tropical fruit is hand-picked and
graded based on the producer's experience and intuition,
the quality is uncertain. To ensure sales of high quality
pineapples, it is necessary to employ nondestructive
quality detection and sorting based on the internal quality
of the fruit. The possibility of sorting pineapples
using Near Infrared Spectroscopy (NIR) to determine
sugar content and acidity, the main quality determinants,
was studied.
Materials
Materials and Methods
One-hundred-and-forty sound pineapples (Ananas
comosus L.: cv. N 67-10) harvested in Higashi-son,
Okinawa Prefecture during June-July 1992 and 40
sound mangoes (Mangifera indica L.: cv. Irwin) were
selected and transported by air at normal temperatures to
Hamamatsu, Shizuoka Prefecture and used for the
experiments. Tables I and 2 give the main physical
characteristics of the experimental fruit.
Measurement of the infrared spectrum
A Nireco model 6500 near infrared spectrophotometer
was used to measure the infrared spectrum. The
pineapple was placed so that thc light beam was at right
angles to the surface of the fruit, which was covered with
* FANTEC Institute. 630 Sasagasl'. lIamamatsu. Shizuoka.
435 Japan.
t University of the Ryukyus. 1 Senbaru. Nishihara. Okinawa.
903·01 Japan.
385
a black cloth to avoid the influence of external light. A
specific spectrum irradiated onto the sample and the
reflected light from the centre section of the sample was
sent to the detector and the absorbance measured. Four
places were chosen along the equator of the fruit as the
testing areas and the near infrared beam was irradiated
at 2 nm intervals from 4{X) to 2500 nm onto the sample
and the average absorbance measured. This was
repeated 50 times.
Table 1. Average values and standard deviations of the
shape and components of pineapples
----------------------------------_.------
Components Average S.D.
Mass (g) 1275.70 58.70
Width (mm) 114.20 3.50
Height (mm) 142.70 7.70
Sugar content (Brix) 14.08 U9
Acidity (mg!l00 mL) 3.02 0.12
Hardness of peel (kg) 3.18 0.32
Hardness of flesh (kg) 1.30 0.15
Table 2. A vcrage values and standard deviations of the
shapes and components of mangoes
Components Average S.D.
Mass (g) J I 1.90 31.60
Width (mm) 68.90 2.50
Height (mm) 105.10 3.50
Sugar content (Brix) 12.30 1.80
Acidity (mg/lOO mL) 0.65 0.08
Hardness of peel (kg) 1.11 0.1 I
Hardness of flesh (kg) 0.42 0.06
Measurement of the sample components
Hardness of peel and flesh, and the sugar content and
acidity were measured. A fruit hardness tester was used
to measure the hardness or the peel in the same area as
the near infrared spectrum was determined. The flesh in
the area used to measure the ncar infrared spectrum was
excised, and the juices squeezed out by hand. An Atago
model PR-I digital refractometer was used to measure,
as sugar content, the soluble solid content. A Touwadenpa
model AT-IOO fruit acid meter was used to
measure the acidity of juice, as citric acid.

the lower portion of the core contained the highest sugar
content and the lower portion of the peel was lowest,
\vhile the centre portion had an average sugar content.
The centre portion also showed average acidity,
Table 5. Distribution of sugar content and acidity according
to the portion of the pineapple
Portion Sugar content Acidity
(Brix) (mg/IOOmL)
Upper portion of the peel 11.633 1.979
Upper portion of the core 12.0()() 1.929
Middle portion of the peel 14.3CX) 2.097
Middle portion of the core 14.267 2.013
Lower portion of the peel 14.7CX) 1.9Rg
Lower portion of the core 15)mO 1.974
Total average 14.078 2.019
3S7
Conclusion
The results of this analysis suggest that it may be feasible
to use NIR for measuring internal quality of pineapple
and mango.
References
Kohda. Y. 1990. Brand planning of agricultural products. hrand
influence of Okinawa grown pineapple in response to liheralisation.
ed. National Association of Agricultural Reformation.
Tokyo. Gyosei Publishing, Inc" 145-161.
ODA (Okinawa Development Agency) 1990. Annual statistics
of Okinawa agriculture. forestry and fisheries. 18th cd.
Naha. Okinawa Development Agency. Okinawa General
Bureau, 74-77.
OPG (Okinawa Prefecture Govel1lment) 1990. Annual statistics
of Okinawa. Naha. Department of Okinawa Development
Planning. Sec. of Statistics. 154-156.

Distribution of Minerals in Alphonso Mango during
Ripening
K. Hari Babn and Shanthakrishnamnrthy*
MINERAL analysis has been used to predict the susceptibility
of fruits to physiological disorders (Perring
1986). The influence of fruit minerals on keeping quality
and postharvest physiological disorders is well
known in apples, pears, and other temperate fruits, but
little is known on their effects in mango. It is now recognised
that the mineral nutrient status of the fruit
during ripening is a major factor in postharvest storage.
Although the calcium content of Alphonso mangoes
with a postharvest ripening disorder known as 'spongy
tissue' has been shown to be lower than in healthy fruit,
there have been no studies of the the mineral composition
of fruit during ripening, the object of the study
reported here.
Materials and Methods
Healthy, ripening fruits were selected for mineral analysis
in two consecutive years (1991 and 1992). Calcium
(Ca), potassium (K), sodium (Na). and phosphorus (P)
were determined using the fruit at edible ripe stage (9
days after harvest). They were estimated in peel and six
different regions of pulp tissues as indicated in Table I.
The peel and pulp of the six regions were collected from
10 fruit in each replicate for three replications. Samples
were cut into small pieces, mixed well. and representative
samples weighed and then dried to a constant
weight in a hot-air oven at 70±2°C for 48 hours. The
dried samples were subjected to wet digestion and used
to estimate concentrations of the four minerals. Estimation
of Ca, K, and Na was by Elico Flame Photometer
(Model L-22A). P was measured using a Spectronic
Model 1201.
Results and Discussion
Measured concentrations ofCa, K. Na, and P in the peel
and six different pulp regions of Alphonso mango fruit
are give in Table I. In general it was observed that
mineral concentrations were higher in the peel than in
the pulp. Within the pulp, mineral composition varied
between the regions selected.
It was observed that the basal part of the pulp tissues
had the highest Ca concentration, followed by middle
* IIHR. Division of Post Harvest Technology, Hessaragatta
(Post). Bangalore. India, Pin 560 089.
388
and apical portions of the pulp. Further, the pulp closest
to the peel contained more Ca than pulp close to the
endocarp. A similar trend was observed by Gun jate et al.
(1979), who also reported that the occurrence of spongy
tissue in the apical part of the pulp nearest the endocarp
was maximal at low Ca concentrations.
The highest K concentrations were recorded in pulp
tissues in the middle of the fruit. This suggests that the
relative concentrations of K in different parts of the pulp
are the opposite to those of Ca. Both Rangwala (1975),
who studied spongy tissue of Alphonso mango, and
Burdon et al. (1991), who investigated softnose-alTected
tissue of Beverly mango, observed higher K and lower
Ca concentrations associated with these disorders. This
suggests that K may also have an important role in
development of spongy tissue.
It was observed that pulp tissues close to the peel had
a higher Na content than those close to the endocarp, but
there was no definite trend in concentrations observed
between the different portions of the pulp, namely basal,
middle, and apical parts of the fru it.
Higher P concentrations were found in pulp tissues in
the middle part of the fruit, followed by pulp tissues in
apical and basal regions. Further, lower P contents were
recorded in pulp ncar the peel than the pulp near the
endocarp. Overall, it was observed that the pulp tissues
close to the endocarp had higher amounts of K and P
with low Ca levels, which correlates with conditions
conducive to occurrence of spongy tissue reported by
Subramanyam et al. (1971), Rangwala (1975), and
Shanthakrishnamurthy (1981).
References
Burdon. J.N., Moore, K.G. and Wainwright. H.G. 1991. Mincral
distribution in mango fruit susceptible to the physiological
disorder softnose. Scientia Horticulturae, 48, 329-336.
Gunjate. R.T., Tare, S.J .. Rangwala. A.D. and Limaye,V.P.
1979. Calcium content in Alphonso mango fruits in relation
to occurrence of spongy tissue. Joumal of Maharastra Agricultural
University, 4{21.159-161.
Perring, M.A. 1986. Incidence of bitler pit in relation to the
calcium content of apples, calcium distribution in the fruit.
Journal of the Science of Food Agriculture. 37. 709-718.
Rangwala, A.[). 1975. Changes in chemical composition of
Alphonso mango fruits during ripening with particular reference
to spongy tissue. M.Sc.(Ag) Thesis. Konkon Krishi
Vidyapccth, Dapoli, India.

Shanthakrishnamurthy 1981. Chemical studies on mineral
breakdown in Alphonso mango (Mangifera)ndica L.) Journal
of Horticultural Science, 56, 247-50.
Subramanyam. H., Shanthakrishnamurthy, Subhadra. N. V ..
Table I. Distribution if minerals (Ca. K, Na, and P) in Alphonso mangoes during ripening
Tissue Calcium (mg/g DW) Potassium (mg/g DW) Sodium (mglg DW)
1991 1992 1991 1992 1991
Peel 109.0 liD 772.0 797.0 42.4
xI 75.0 78.1 604.0 614.0 35.8
x2 53.8 52.1 636.0 648.0 34.7
YI 65.7 62.7 680.0 652.0 41.1
Y2 53.2 41.4 691.0 684.0 38.1
zi 52.7 56.4 576.0 603.0 38.4
z2 38.8 39.3 620.0 631.0 39.7
Mean 64.0 63.9 654.0 616.0 38.6
SEM± 1.20 0.99 4.87 4.10 0.48
CDat5% 4.57 3.77 18.54 15.61 1.82
x I and x2 are outer (near pee\) and inner (near endocarp) pulp tissue from Ihe basal part of Ihe fruit.
Y I and Y2 are outer (near pee\) and inner (near endocarp) pulp tissue from the middle part of the fruit.
zi and z2 are outer (near peel) and inner (near endocarp) pulp tissue from the apical pari "fthe fruit.
389
Dalai, V.S., Randwa. G.S. and Chacko, E.K. 1971. Studies
on internal breakdown a physiological ripening disorder in
Alphonso mangoes (Mangifera indica L.). Tropical Science,
13,203-210.
1992
23.1
19.6
18.6
20.1
19.2
19.8
18.6
19.8
0.35
1.33
Phosphorus (mg/g DW)
1991 1992
156.8 147.9
94.6 87.4
127.2 122.2
130.8 128.3
150.9 141.2
116.1 108.2
140.8 116.4
131.0 121.7
US 1.05
5.18 3.99

Effect of Calcium on Physicochemical Changes in Alphonso
Mango during Ripening and Storage
K. Hari Babu and Shanthakrishnamurthy*
ALPHONSO is one of the most popular mango varieties
grown in India. The marketing potential for mangoes is
limited due to their high perishability. Under tropical
ambient conditions fruits ripen rapidly after harvest at
the green-mature stage, become soft in texture and are
predisposed to injury. Appropriate technology to extend
the shelf life and reduce postharvest losses of mangoes
is therefore required. The possibilities for low temperature
storage are limited by the high capital cost and susceptibility
of mangoes to chilling injury at temperatures
below 15°C (Shanthakrishnamurthy and Joshi 1989).
Modified atmosphere storage of mangoes is also limited
by high incidence of rot, fernlented odours, and internal
breakdown of fruit (Gautam and Lizada 1984). Calcium
(Ca) is known to be an essential plant nutrient involved
in a number of physiological processes concerning
membrane structure and function, and enzyme activitys
(Jones and Lunt 1967). Ca compounds have shown
promise in the quality retention of fruit and vegetables
through maintaining firmness, reducing respiratory rate
and ethylene evolution (Pooviah 1986), and decreasing
storage rots (Conway and Sams 1984). The present
study was undertaken to investigate the effect of preand
postharvest Ca treatments on various physicochemical
changes and shelf life of Alphonso mangoes during
ripening and storage.
Materials and Methods
Pre-harvest calcium chloride (CaCI 2 ) sprays were
applied to Alphonso mango trees in the orchard of
I.I.H.R., Hessaragatta, Bangalore during 1992. CaCl2
solutions containing 5000 and 10000 ppm calcium concentrations
were sprayed at 5 intervals on 5 trees per
treatment. The first spray was applied 15 days after fruit
set followed by second and third sprays of fortnightly
intervals. forty-five days after fruit set two more sprays
were applied at monthly intervals. Teepol at 0.1 % was
used as a surfactant. The trees were sprayed until dripping.
Fruit were harvested 110 days after fruit set. Lots
of 20 fruits in 3 replications were prepared and used for
postharvest dip treatments in CaCI 2• These were made
by infiltrating under vacuum (250 mm Hg) for 5 minutes.
Pre- and postharvest Ca-treated fruit were stored at
* I1HR, Division of Post Harvest Technology. Hessaragatla
(Post). Bangaiore. India, Pin 560089.
390
ambient temperature (28 ± 2°C) and relative humidity
(40-60%) and various physicochemical parameters
estimated during ripening and storage. An Instron 4201
meter was used to measure firmness; total soluble solids
(OBrix) were estimated with an Erma hand refractrometer;
and chemical constituents (acidity, reducing and
total sugars, starch, and carotenoids) were estimated
following the procedures suggested by Ranganna
(1986).
Results and Discussion
It was observed that untreated fruit had maximum physiological
loss of weight - PL W (18.13%) as compared
with both pre- and postharvest Ca-treated fruit, 19 days
after harvest (Table I). Among all the treatments, the
fruit infiltrated with 4% CaCI2 showed minimum PL W
(12.61%). Minimum PLW has been reported in fruit
sprayed with pre-harvest CaCl2 in Amrapali (Singh et al.
1987) and in Julie mangoes (Mootto 1991).
At harvest, the mean fruit firmness with (16.81 kg/
cm2) and without (10.34 kg/cm2) peel was much lower
in control fruit with (1.97 kg/cm2) and without (0.59
kg/cm2) peel at 15 days after harvest, whereas fruits
infiltrated with 4% CaCI2 showed maximum firmness
both in fruits with (3.98 kg/cm2) and without peel (1.81
kg/cm2 ) even at 19 days after harvest. This was probably
due to added calcium in the peel and pulp helping to
maintain the structure and function of cell walls. Similar
results on retention of firmness by calcium treatment
were also reported in apples by Poovaiah (1986). Formation
of calcium pectate by added Ca, a substance not
readily available to pectic acid degrading enzymes, was
reported by Bangerth (1979).
The initial mean titratable acidity of fruit pulp was
3.92%. This fell to a minimum of 0.17% 15 days after
harvest in control fruits. Among the treated fruit, maximum
acidity (1.81 %) was recorded in fruit infiltrated
with 4% CaCl2 while minimum acidity (0.76%) was
recorded at 15 days after harvest in fruit treated with
10000 ppm Ca as a preharvest spray. Higher acidity
following CaCl 2 treatment either as a preharvest spray
or postharvest dipping in Amrapali mangoes was
reported by Singh et al. (1987). Tirnlazi and Wills
(1981), however, observed no difference in acidity
levels of 'Kensington Pride' mangoes following postharvest
dipping with CaCI2.

Effect of Low Temperatures on Storage Life and Quality
of Car am bola (Averrhoa carambola L.) cv. B17
Rohani Md Yon and Mohd Yunus Jaafar*
THE carambola or starfruit (Averrhoa carambola L.) is
a popular dessert fruit in Malaysia. In recent years it has
gained popularity as an export commodity, with B 17 the
main commercial cultivar. B 17 fetches a higher price in
local markets. There is potential for this cultivar to be
developed as an export commodity since the tlavour and
taste of its fruit are highly acceptable to consumers.
Since carambola fruit are non-climacteric (Oslund
and Devenport 1981; Lam and Wan 1983) they have to
be harvested at a time that will maintain the sweetness
of the fruit. Studies by Siti Halijah and Md. Yunus
(1992) indicated that the fruit can be harvested at 11-13
weeks after fruit set.
There have been a number of studies on low temperature
storage of carambola (Oslund and Devenport
1981; Lam 1983; Lam and Wan 1983; Wan and Lam
1984; Kenny and Hull 1986; Campbell et al. 1987), but
none involving the B 17 cultivar. The main objective of
the study reported here was to determine the storage
potential of the B 17 cultivar. The effects of low temperatures
on the quality and storage life of the fruits were
also investigated.
Materials and Methods
The carambola were obtained from a commercial farm
in Raub, Pahang, 180 km north of Kuala Lumpur. Bagging
was carried out when the fruit were about 5-6 cm
long (about a month after fruit set) to prevent fruit tly
attack. Bagging also helped to give the fruit an attractive
glossy appearance.
The fruits were harvested at 10, II, 12, and 13 weeks
after fruit set and brought back to the Food Technology
Research Center where the storage studies were conducted.
At each harvesting date, fruit with predominant
colour grade were selected and randomly alloted to 4
replicates with 10 fruits per replicate. Each replicate of
fruit was then placed into a corrugated fibre-board box
lined with perforated polyethylene bag. The boxes were
stored at 5,10, 15, and 20°C and removals were carried
out every fortnight until the fruit were senescent or diseased.
At each removal, half the fruit were also placed
at ambient temperature (28°C) for a week to determine
* Malaysian Agricultural Research and Development Institute
(MARDI), GPO Box 12301. 50744 Kuala Lumpur. Malaysia.
396
quality of fruits after storage at low temperature. A randomised
complete block design with harvest and storage
temperature combinations forming the blocks
(Cochran and Cox 1957) was employed in data collection.
The changes in skin colour, fimmess, and develop ..
ment of disease were recorded. For skin colour, the
changes were recorded using a scoring system where I
= green, 2 = light green, 3 = yellowish green, 4 = more
yellow than green, 5 = more orange than yellow, and 6
= full orange.
Firmness of the fruit was determined by puncture test
using an Instron 1140 machine. The puncture test was
carried out using the 7 mm diameter Magness Taylor
probe which was driven into the horizontal surface of the
fruit until punctured. The machine was operated using a
cross-head speed of 50 mm/min and a chart speed of 500
mm/min.
Changes in disease development were also recorded,
using a scoring system where 0 = no disease, I = < 25%
of fruit affected, 2 = 25-50% of fruit affected, and 3 = >
50% of fruit affected.
The fruits were analysed for pH, percentage of total
soluble solids (TSS), total titratable acidity (TT A), and
total sugars (TS).
The pH was determined by blending whole fruit at
room temperature; readings were taken using an Orion
digital pH meter model SA520. TSS of the expressed
juice of the whole fruits was measured using an Atago
digital refractometer (0-32° Brix). TTA was determined
by titrating a known weight of blended fruit sample to
pH 8.1 with 0.1 N NaOH and the results expressed as
percentage of oxalic acid (Lam 1983). Total sugars were
analysed by the method of Lane and Eynon (AOAC
1975).
Analysis of variance and Duncan's Multiple Range
Test were performed on data (Gomez and Gomez 1984;
Steel and Torrie 1980). Correlation analyses were also
perfomled on the data to determine the relationship
between the varieties. The SAS procedures were utilised
for data analysis using a mainframe computer (SAS
Institute 1985).
Results
The results indicated that there were significant changes
in the physical attributes of B 17 carambola during stor-

(Table 4). The shorter storage life of the younger fruit
may be due to chilling injury, an environmental effect on
younger fruit conducive to the growth of microorganisms,
or that the fruit had lower resistance to diseases
than the mature fruit (Lam 1903 J. At higher storage
temperatures (I5 and 20°(,) the fruit could be stored for
only about a week before they decayed due to rapid
development of diseases.
Table 10. Dcvclopmcm of discases on BI7 carambola placed
at ambient temperature after 2 weeks storage at
SoC and 10°C
Maturity Days at Temperature (0C)
(weeks) ambient
S 10
10 0 O.OOa O.OOa
3 O.IOa O.OOa
S O,43b OAOb
7 0.66(' 0.70c
II 0 0.00 O.G3
3 0.00 1.30b
S 0.00 2.03c
7 0.43 2.63d
12 0 O.OOa 0.17a
3 O.OOa 0.37a
S 0.12al1 0.373
7 0.23b 0.9711
13 0 O.Of>a O.03a
3 O.07a O.04a
S 0.63b O.77b
7 0.73b O.96b
Mean separation within column. at each maturity by DMRT at 5%
level. Means with the same letter are not significantly differen!.
Table II. Development of diseases on B 17 carambola placed
at ambient tempt.'rature after 4 weeks storage a\ 5
and 10°C
Maturity Days at Temperature (OC)
(weeks) ambient
S 10
12 0 0.17a 0.17a
-' O.37ab 0.6-'b
S 0.5311(' 1.01('
7 0.73c I.SOd
13 0 O.OOa O.OOa
-' O.40b O.46b
S 0.8Sc 1.0Oe
7 I.IOd I.OOc
Mean separation within column, at each maturity by DMRT at 5(',(,
level. Means with the same leller are not significantly different.
Note: No data available for fruits harvested at JO and II week.s after
fruit set because all fruits already decayed or diseased.
Lower storage temperatures also help to preserve the
quality of the fruit. This is because carambola stored at
400
low temperatures have lower metabolic and respiration
rates than those stored at higher temperatures (Lam and
Wan 1987). The low metabolic rate helps to slow down
the ripening process. This was exhibited in the slow or
gradual change in colour and firmness of the fruit when
stored at 5°C as the ripening process was retarded. At
this temperature, the colour index at harvest could be
maintained, while it was impossible to stop the ripening
process at higher temperatures. The rate of ripening was
faster when the temperatures were increased, as indicated
by a decrease in the firmness of the fruits (Table
3). At higher temperatures, softening of the tissues may
also be accelerated due to senescence. This process was
particularly rapid when the fruit were held at ambient
tem perature.
Changes in the chemical quality were also affected by
fruit maturity and storage temperatures. All these
changes were also affected by the metabolic rate of the
fruit. At low temperatures, both the mctabolic and respiratory
rates were reduced. Thus. the change in pI!.
TSS, and TS was very gradual due to the low metabolic
rate of the fruit.
During storage, the pH in the younger fruit continued
to increase gradually, indicating that the ripening process
was still in progress especially during the first 2
weeks (Table 6). No significant increase in pH was
observed after that, indicating that the ripening process
was retarded due to reduction ill fruit metabolism.
However, during the first 2 weeks storage the pH rapidly
increased to values approaching those of ripe fruit.
In general, there was significant reduction in both the
percentage TSS (Table R) and TS (Table 9) which
clearly indicated that these components were being utilised
in the metabolic processes of the fruit. TIle rate of
reduction was more rapid when the temperature was
increased. correlating with higher rates of respiration.
Conclusion
Carambola cv. B17 can be stored at low temperatures.
Mature fruits can be stored longer since they are more
resistant to disease development. Fruits harvested at 12
and 13 weeks after fruit set can be stored for 4 weeks at
5 and iOoC. Since carambola arc non-climacteric fruit
(Oslund and Devenport 1981; Lam and Wan 1983) harvesting
at this maturity stage gives better quality fruits in
terms of flavour, colour development, and taste (Siti
Halijah and M. Yunus 1992).
Fruits harvested at 10 and II wecks after fruit set can
be stored for 2 weeks at low temperatures (5 and 10°C J.
At higher temperatures (15 and 20 0 e), the fruit can be
stored for about I week before they decay, mainly due to
diseases. However, it is not advisable to harvest the fruit
at these shorter times after fruit set, since they have a
shorter storage life and their colour and flavour do not
develop fully.

Diseases also developed rapidly on fruits that had
been stored at 5 and 10°C when held at ambient temperature.
At this temperature the fruits should be marketed
3-5 days after removal from cold storage.
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