1
CARD PROJECT 050/04 VIE

Improvement of export and domestic markets for
Vietnamese fruit through improved post-harvest and
supply chain management

MAINTAINING FRUIT QUALITY AND INCREASING SHELF LIFE
OF POMELO IN THE MEKONG DELTA OF SOUTHERN VIETNAM

By Robert Nissen
1
, Nguyen Duy Duc
2
, Ms San Tram Anh
2
, Ms Tran Thi Kim Oanh
2
, Mr Vu Cong
Khanh
2
& Mr Ngo Van Binh
2
,

1
Queensland Department of Primary Industries and Fisheries (DPI&F) , Maroochy Research

Khanh Du Street, District 1, Ho Chi Minh City, Vietnam.

INTRODUCTION
In Southern Vietnam, traditional wet market supply chains for agricultural fresh food are now giving way
to new supermarket-led supply chain systems. The rapid transformation in the fruit and vegetables
sector is due to the meteoric rise of supermarkets, hypermarkets, superstores, neighborhood stores,
convenience stores, discount stores in Southern Vietnam. This change is impacting on both the
upstream and downstream agricultural food supply chain participants through demands for safe, high
quality and sustainable-produced fresh products and the greatest impact is being felt by the small
farmers of southern Vietnam. Problems with traditional procurement supply chain practices include
low- or no product standards, supply inconsistencies, highly variable transaction costs and limited or
sequestered market information.

Supermarkets are now setting new procurement practices and supply systems which focus on reducing
costs and improving quality to enable them to sell at lower prices. This will allow them to win over
consumers and obtain a larger share of their target market. The ability of many small farmers,
collectors and wholesalers in the Mekong Delta of Vietnam to meet safe food levels and quality
demands of domestic and overseas supermarkets can only be obtained through investing in
improvements in their production and supply chain practices.

Implementation of new production and post–harvest practices and the modernisation of these supply
chains may prevent some small farmers from participating. Many small farmers will have to develop
risk minimisation strategies, such as forming groups, implementing new crop management and
production systems, improved packaging, more efficient transport methods and handling practices to
provide a safe, competitively priced quality product. Understanding how to develop new supply chains
and where to make changes is essential if farmers and all chain participants are to benefit.

Many farmers are now realising that pomelo is a perishable fruit and traditional chains may have to
change. Pomelo fruit suffer severely from moisture loss. Loading and unloading occurs at the local
markets in the hot sun, speeding up the desiccating of the fruit. This moisture loss changes the fruit

this experiment. Experimental design consisted of three treatments of 10 fruit per rep sampled every 7
days for 12 weeks. Treatments applied were:
1. Control
2. Citra Shine Special Wax applied to the fruit
• CITRASHINE is a shellac-based wax formulated with purified natural secretion and
water-soluble emulsifying agents. It does not contain any solvents but water and all
ingredients are approved for use on foodstuf by the Health regulations in most
countries. This product is USFDA approved.
• CITRASHINE is stable and anti-transparent and the long-lasting shine which it
provides improves citrus fruit appearance and skin resistance, increasing the fruit
market value. In addition CITRASHINE controls dehydratation and prevents fruit from
excessive weight loss. Fruits were cleaned by detergent deccosol before apply the
wax to remove dirt, dust and foreign material.
3. Vacuum sealed polyethylene plastic film applied to the fruit (wrapping)
• A Lavezzini Vacuum Packaging Systems, Model Boxer was used to wrap and seal the
pomelo fruit in a 0.014 mm Liner Low Density Polyethylene (LLDPE) plastic film.
FRUIT MEASUREMENTS
Assessments undertaken were:
• Average fruit weight in grams and percentage moisture loss over time
• Skin colour change over time using a Minolta Chromometer CR 200 and expressed as L a b
values
• Titrateable Acid measured using 10 grams of flesh in 100ml of double distilled water and
macerated. This solution was then filtered through cotton wool and 10 mls of juice was
collected and 2 drops of phenolphalayene indicator was added and titrated with Sodium
Hydroxide (NaOH) 0.1 normal solution, until colour change occurred.

4
• Total soluble solids or degree Brix, was measured using a temperature compensation hand
held Atago Refractometer Model N-1E.
• Vitamin C content was measured using Association of Analytical Chemists (AOAC)

 F: mg ascorbic acid equivalent 1ml standard 2,6 diclorophenol
indophenolat natri
( F=
Y
2
).
• Taste evaluations were carried out by an expert panel of 12 people established at SIAEP
laboratory using the hedonic scale (1-9):-
1 = dislike very much
3 = dislike
5 = neither dislike or like
7 = like
9 = like very much
RESULTS
LOSS IN FRUIT WEIGHT (MOISTURE)
Fruit weight loss was greater for the Control and Vacuum Wrapping treatments compared to the Citra
Shine Special Wax treatment (Figure 1). Moisture loss for the Vacuum Wrapping and Citra Shine
Special Wax treatments was reduced by 13% and 22% respectively compared to the control treatment.
The control treatment and Vacuum Wrapping treatment fruit shelf life was 63 days and the fruit treated
with Citra Shine Special Wax was 77 days.

Control treated fruit at 63 days were extremely shriveled. This was due to sever moisture loss and
disease had affected the internal eating quality of the fruit. The Vacuum Wrapped treated fruit were

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also shriveled, but the fruit had not desiccated to the same degree as the control treated fruit at day 63.
The Citra Shine Special Wax treated fruit did not reach the same level of desiccation as the Vacuum
Wrapped treated fruit until day 77. The Control treated fruit had the highest rate and the greatest
moisture loss of the three treatments (Figure 2).


Days
0 7 14 21 28 35 42 49 56 63 70 77
Moisture loss (%)
0
10
20
30
40
Control
(power) y=a+bx
c
r
2
0.9989934473
a=-3.15094878
b=3.139496644
c=0.602550012

Figure 2. Control treatment, fruit moisture loss over time Days
0 7 14 21 28 35 42 49 56 63 70 77
Moisture loss (%)
0
10
20
30
40
Citra Shine Special Wax

c=0.672818004

Figure 4. Vacuum wrapping treatment, fruit moisture loss over time End of shelf life is based on external appearance and the characteristics used are:
• fruit have a soft leathery feel
• fruit are highly shriveled due to moisture loss
• neck of the fruit is sunken and more pronounced
• skin colour changes from bright yellow colour to a dull deeper yellow
• disease area on infected fruit increase in size rapidly.

Internal appearance indicators for end of shelf life is:-
• internal browning of the segments and albedo
• juice sacks are soft and spongy
• juice sacks are not easily separated from the segment
• disease areas are visible in the flesh. 8

Lightness 25% Lightness 50% Lightness 75%
Figure 12. Colour diagrammatic representation of L* a* b* colour space values
Note: Colour show here may not be a true representation of colour observed by the naked eye as these colours patches are
dependent computer, screen and printer settings used to display or print this report. S
KIN COLOUR READINGS
Traders, collectors, packing agents, wholesalers, retailers and consumers look at the skin colour, and
use this as one of the determinates of fruit maturity and ripeness. Therefore, in this experiment we
have tried to establish the effects of the anti-transparent and vacuum wrapping on skin colour. 12
Survey work conducted by the CARD Project 05004/ VIE found:
• Wholesalers prefer to purchase Nam Roi pomelo fruit that are light green in colour, as this they
regard this as a sign of freshness and maturity. If fruit are too yellow they are regarded as
being overripe. IF fruit are too green, they are
• Wholesalers also prefer to purchase class 1 pomelo fruit with stalks (>10cm) and leaves
attached, this is a sign of freshness
• Under high temperature conditions in Vietnam pomelo fruit ripen quickly, lose moisture and
shrivel, then breakdown due to disease (fruit rots)

Table 2 provides a comparison of representative colour space over time taken of the Control, Citra
Shine Special Wax and Vacuum Wrapping treatment fruit.

Readings L* 62.35; a* -11.12; b* 43.65 L* 61.56; a* -14.04; b* 37.83 L* 62.63; a* -10.66; b* 28.26
49

Readings L* 63.79; a* -9.09; b* 47.27 L* 61.57; a* -13.06; b* 39.12 L* 58.87; a* -8.89; b* 27.18
56

Readings L*64.58; a* -6.80; b* 47.77 L* 62.55; a* -10.97; b* 40.98 L* 67.44; a*-7.65 ; b* 34.38
63

Readings L* 64.78; a* -4.32; b* 48.85 L* 66.09; a* -8.27; b* 45.40 L* 68.81; a* -5.67; b* 36.79
70 Readings L* 64.16; a* -6.13; b* 45.22
77 Readings L* 68.02; a* -3.18; b* 50.16

The Vacuum Wrapped treated fruit reach a similar skin colour 7 days (1 week) after the Control Treated
fruit (Table 2). Fruit treated with Citra Shine Special Wax reach a similar yellow skin colour 14 days (2
weeks) later than the Control treated fruit (Table 2). Therefore, based on skin colour, the Citra Shine
Special Wax increased the fruit shelf life by 2 weeks and the Vacuum Wrapping increased shelf life by 1
week.

All citrus are non-climacteric fruit, meaning that they ripen gradually over weeks or months. External
color changes during ripening, but is a function of climate more than ripeness, and a very poor indicator
of maturity. The best indices of maturity for citrus are internal Total Soluble Solids (
o
Brix or sugar),

58
60
62
64
66
68
70
Control
Citra Shine Special
Vacuum Wrapping

Figure 13. Comparison of the average L* colour space values for the Control, Citra Shine Special Wax
and Vacuum Wrapping Treatments for Nam Roi Pomelo.
15
Days
0 7 14 21 28 35 42 49 56 63 70 77
L* colour space
50

Figure 15. Citra Shine Special Wax treatment L* colour space change over time
16
Days
0 7 14 21 28 35 42 49 56 63 70 77
L* colour space
50
55
60
65
70
Vacuum Wrapping
y=a+bx
r
2
=0.8837896690
a=57.78614059
b=0.148571500

Figure 15. Vacuum Wrapping treatment L* colour space change over time
Vacuum Wrapping was the slowest and slowly increased until day 35 and then increased rapidly until
day 63 (Figure 19).

Days
0 7 14 21 28 35 42 49 56 63 70 77
a* colour space
-18
-16
-14
-12
-10
-8
-6
-4
-2
Control
Citra Shine Special Wax
Vacuum Wrapping

Figure 16. Comparison of the average a* colour space values for the Control, Citra Shine Special Wax
and Vacuum Wrapping Treatments for Nam Roi Pomelo.

0 7 14 21 28 35 42 49 56 63 70 77
a* colour space
-20
-15
-10
-5
0
(power)y=a+bx
c
r
2
=0.96121494
a=-15.867733
b=0.00011966
c=2.66249
Citra Shine Special Wax

Figure 18. Citra Shine Special Wax treatment a* colour space change over time 19

20
S
KIN B* COLOUR SPACE
For the b* colour space readings, all three treatments had a straight line linear relationship and
changed colour from blue to yellow colour (Figure 20). The skin b* colour space for the Control treated
fruit changed from green to full yellow in 49 days (Figure 21), the Vacuum Wrapping fruit changed from
green to full yellow in 56 days (Figure 22) and the Citra Shine Special Wax treated fruit changed from
green to full yellow in 63 days (Figure 23). Days
0 7 14 21 28 35 42 49 56 63 70 77
b* colour space
25
30
35
40
45
50
55
Control
Citra Shine Special Wax
Vacuum Wrapping

Figure 20. Comparison of the average b* colour space values for the Control, Citra Shine Special Wax
and Vacuum Wrapping Treatments for Nam Roi Pomelo.


=0.98358781
a=28.74766
b=0.330902975
Control

Figure 21. Control treatment b* colour space change over time
Days
0 7 14 21 28 35 42 49 56 63 70 77
b* colour space
25
30
35
40
45
50
55
y=a+bx
r
2
=0.95109987
a=28.564892
b=0.2463527
Citra Shine Special Wax

Figure 22. Citra Shine Special Wax treatment b* colour space change over time
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T
OTAL SOLUBLE SOLIDS (TSS) OR DEGREE BRIX (
O
BRIX)
For this experiment, no relationships could be established between time and change in Total Soluble
Solids (
o
Brix). Figure 24 shows the Control treatment reaching a peak of 13
o
Brix on day 49 then
dropping sharply to 9
o
Brix on days 56 and 63. This drop was due to the fruit being over ripe and
breaking down internally. The Citra Shine Special Wax and Vacuum Wrapping treatments
o
Brix levels
continued to rise from day 1 reaching 12
o
Brix, even when the fruit had reach the end of their shelf life
on day 63 and day 77 respectively (Figure 24). Days

by 20% on day 63 (Figure 25).

Fruit treated with Vacuum Wrapping also increased in acid by 16% on day 14, peaking at 0.86% acid.
Fruit then slowly decreased by 6% on day 21, stabilised for 3 weeks before dropping sharply by 25% to
reach a low on day 63.

The Citra Shine Special Wax treated fruit had a significantly lower acidity. The initial rate of increase
was only half that of the Control and Vacuum Wrapping treatments. The acidity level for this treatment

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peaked at 0.79%, about 9% lower that the Control and Vacuum Wrapping treatments. The acid level
decreased at a slower rate compared to the Control and Vacuum Wrapping treatments. Fruit acid then
decreased by 25% to be 0.60% on day 77. The amount of decrease is similar to the decrease in acidity
for the Control and Vacuum Wrapping treatments, 20% and 25% respectively. Days
0 7 14 21 28 35 42 49 56 63 70 77
Titrateable Acid (%)
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
Day vs Control
Day vs Citra Shine Special Wax
Day vs Vacuum Wrapping

Vaccum Wrapping

Figure 15. Comparison of the average Vitamin C content (mg/100g) between treatments for Nam Roi
Pomelo. For the Control treatment the Vitamin C content starting at 50.79mg/100g and by day 63, increased
11% to 56.61mg/100g. The Citra Shine Special Wax treatment dropped slightly, from 50.79 mg/100g
on day 1 to 49.43mg/100g on days 35 to 42, before increasing 12% to 57.15mg/100g on day 77. The
Vacuum Wrapping treatment remained at about 50.5 mg/100g for the firs 3 weeks (days 7, 14 and 21)
before rising to a peak on day 35 of 52.9mg/100g then falling 15% to a low of about 45mg/100g on
days 56 and 63.