Báo cáo nghiên cứu khoa học " MAINTAINING FRUIT QUALITY AND INCREASING SHELF LIFE OF POMELO IN THE MEKONG DELTA OF SOUTHERN VIETNAM " pot

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

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

Station, PO Box 5083 SCMC, Queensland, Australia, 4560

2 Southern Sub-Institute of Agricultural Engineering and Post-Harvest Technology (SIAEP), 54

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

MAINTAINING FRUIT QUALITY AND INCREASING SHELF LIFE

OF POMELO IN THE MEKONG DELTA OF SOUTHERN VIETNAM

Robert Nissen1, Nguyen Duy Duc2, Ms San Tram Anh2, Ms Tran Thi Kim Oanh2, Mr Vu Cong Khanh2 &

Mr Ngo Van Binh2,

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

PO Box 5083 SCMC, Queensland, Australia, 4560

2 Southern Sub-Institute of Agricultural Engineering and Post-Harvest Technology (SIAEP), 54 Tran

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

Therefore, this CARD Project set up experiments to evaluate the benefits of developing new harvest practices to improved fruit quality by reducing moisture loss for the pomelo supply chains operating in southern Vietnam

post-METHODOLOGY

Because pomelo fruit suffer from the loss of moisture, this CARD project set up an experiment to reduce this moisture loss and increase shelf life and retail value of pomelo fruit An anti-transparent and vacuumed wrapping of fruit in polyethylene bags were trialed to determine if this moisture loss could be significantly reduced

The pomelo variety “Nam Roi” was chosen as the variety on which to conduct the experiments Nam Roi is famous pomelo variety in Vietnam as the fruit are sought after by many Vietnamese consumers

It has special fruit qualities such as:-

• seedless

• yellow flesh colour

• the flesh is crisp and sweet

TREATMENTS

Fruit assessments were carried out at the SIAEP laboratory in Ho Chi Minh City Treatments were applied to the pomelo fruit and fruit stored on the bench in the laboratory at SIAEP at about 25oC Mature pomelo fruit purchased from the Thuy Duc Wholesale Markets in Ho Chi Minh City were used in 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

• 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) International method 967.21 Procedure used was:

o Take 10 g of fruit flesh and grind with 5 ml Metaphosphoric-acetic solution

o Remove all sample and place into a 100ml flask and add Metaphosphoric-acetic solution until it reaches 100mls and shake

o Filter through absorbent cotton or rapid paper

o Take 10ml of the above solution and place into a 100ml glass beaker

o Titrate this solution with 2,6 diclorophenol indophenolat natri until fast pink colour appears This takes about 2 minutes to occur

o Count amount of 2,6 DCPIP need to titrate 1mg acid ascorbic

ƒ + Take 2 ml standard acid ascorbic solution add 5 ml Metaphosphoric-acetic

ƒ +Titrate with 2,6 diclorophenol indophenolat natri until fast pink colour appears in about 2 minutes (note number ml : y)

o Titrate blank sample with 2,6 diclorophenol indophenolat natri until fast pink colour appears This takes about 2 minutes to occur (note number ml = B)

Calculation

Content of Vitamin C =

P v

V F B X

100 )

ƒ X: ml 2,6 diclorophenol indophenolat natri titrate sample

ƒ V: extracting solution volume ( V = 100ml)

ƒ v: extracting solution volume to titrate (v = 7ml)

ƒ P: amount of sample ( p = 10 gram)

ƒ F: mg ascorbic acid equivalent 1ml standard 2,6 diclorophenol indophenolat natri ( F=

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)

Moisture loss followed a power curve (y=a+bx c) pattern for all treatments See Figures 2, 3 and 4 below

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Control Citra Shine Special Vacuum Wrapping

Figure 1 Comparison of percentage moisture loss in Nam Roi Pomelo fruit between control, Citra

Shine Special Wax and Vacuum Wrap treatments

Figure 2 Control treatment, fruit moisture loss over time

Figure 3 Citra Shine Special Wax treatment, fruit moisture loss over time

Citra Shine Special Wax

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

Figure 5 Control treated fruit day1

Figure 8 Control treated fruit day 63

Figure 9 Citra Shine Special Wax treated fruit day 63

Figure 10 Vacuum wrapped treated fruit day 63

COLOUR READINGS

Minolta Chromameter CR 200 was used to determine skin colour changes of the sampled fruit The colour space measurements are:- L* (positive values indicate lightness and negative values indicate darkness), a* (positive values indicate red as opposed to negative values indicate green), and b* (positive values indicate yellow and negative values indicate blue)

Figure 11 L* a* b* colour space difference ∆E* ab

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 C OLOUR R EADINGS

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

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

Table 2 Skin colour readings from day 1 to day 77 for treatments applied for Nam Roi Pomelo

Table 2 (cont) Skin colour readings from day 1 to day 77 for treatments applied for Nam Roi Pomelo

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 (oBrix or sugar), Titrateable acid content (acid), and the oBrix/acid ratio

S KIN L* C OLOUR S PACE

We found the L* colour space readings for fruit that were Vacuum Wrapped in a liner of low-density polyethylene plastic film were very slightly altered were due to the reflective nature of the plastic if fruit were measured with the wrapping plastic on

Fruit from all treatments ripened and the skin colour changed from a darker colour (green) to lighter, brighter (Yellow) colour with no adverse affects Fruit of the Vacuum Wrapping treatment did not change to a lighter colour at the same rate as the Control and Citra Shine Special Wax treated fruit (Figure 13) The Control, Citra Shine Special Wax and Vacuum Wrapped treatments were straight line

linear relationships (y=a+bx) See Figures 14, 15 and 16 Initially, the change from a darker colour to a

lighter colour was constant for all treatments from day 1 to day 14 The Vacuum Wrapping treatment rate of change slowed until day 49, then increased rapidly to a lighter colour from day 49 to day 63 (Figure 13)

Days

0 7 14 21 28 35 42 49 56 63 70 77

50 52 54 56 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

Figure 14 Control treatment L* colour space change over time

Day vs Traditional method

Figure 15 Citra Shine Special Wax treatment L* colour space change over time

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

S KIN A * C OLOUR S PACE

For the a* colour space (red to green), the Control and Vacuum Wrapped treated fruit remained green until day 28 when the fruit lost the green colour and change to a light yellow colour (Figure 16) All three treatments had similar power curve relationships The Control treatment changed in colour was slow until day 28, and then increased rapidly until day 63 (Figure 17) The Citra Shine Special Wax treatment increased slowly until day 2, and then increased rapidly until day 77 (Figure 18) The Vacuum Wrapping was the slowest and slowly increased until day 35 and then increased rapidly until day 63 (Figure 19)

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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

Figure 17 Control treatment a* colour space change over time

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

-5 (power)y=a+bx c

r 2 =0.98863022 a=-12.452764 b=0 673678e-06 c=3.1207941 Vacuum Wrapping

Figure 19 Vacuum Wrapping treatment a* colour space change over time

S KIN B * C OLOUR S PACE

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)

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

Figure 21 Control treatment b* colour space change over time

Figure 22 Citra Shine Special Wax treatment b* colour space change over time