Subject: Situation of postharvest technology for Vapor Heat

Title of Country Report:
Subject: Situation of postharvest technology for Vapor Heat Treatment
of Mango in Vietnam
Name
: NHAN THI MINH UYEN
Organization: POST ENTRY PLANT QUARANTINE CENTER NO2 –
PLANT PROTECTION DEPARTMENT – MINISTRY OF AGRICULTURE
AND RURAL DEVELOPMENT OF VIETNAM
I. Introduction
In the trend of economic globalization, international agricultural trade is increasing
rapidly year by year. As a member nation of regional and international organizations such
as Asia and Pacific Plant Protection Commission (APPC), ASEAN and WTO, Vietnam is
actively promoting international tread of agricultural products. Particularly, there is strong
interest in exporting high quality tropical fruits to foreign countries.
On the other hand, the increase of international agricultural trade has greatly caused
high risk of human activities assisted dissemination of significant quarantine pests overseas;
many countries have imposed sever restrictions such as prohibition of constraints on the
import of Vietnamese produce to protect their own agricultural products from injurious
pests brought in by imports.
In case of import-banned plant products, access to the freer trade may be gained by
ban lifting through the development and implementation of effective quarantine treatment,
to meet import requirements set by importing countries.
Fruit flies are among important plant quarantine target pests raising barriers to
importation of fresh fruit from Vietnam. Vietnam has to study and find out proper fruit flies
eradication measures while maintaining export fruit quality.
Vietnam produces delicious fruits, to name mango and dragon fruit categorized as a
high export potential group, particularly grown in the Southern part. To date only dragon
fruit has gained export permits to demanding markets such as the US, Japan, Chile on
account of vapor heat treatment effective against all 3 flies species infesting the fruit (JICA
- IPQTF project 2008).
Until early 2012, Vietnam mango has not gained access to demanding markets for
reason of fruit flies infestation.
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Fruit flies control project (ICP/VIE/8823/1999-2000) in Vietnam inventoried and
identified 30 species, among them Bactrocera correcta Bezzi infesting guava and the
oriental Bactrocera dorsalis Hendel predominant in fruit crops nationwide, they particularly
infest mango which also suffers from Bactrocera carambolae Drew and Hancock.
According to assessment by Japanese experts from JICA-IPQTF project, studies
should be made to eradicate 4 fruit fly species B. dorsalis, B. correcta, B. carambolae and B.
cucurbitae to gain mango export market access. These fly species are quarantine target
pests or black listed in import produce by many countries beside Japan, such as the US,
New Zealand, South Korea (JICA-IPQTF project, 2006).
Therefore, to allow for fresh mango fruit exportation, Vietnam should sustain
experimentation on fruit flies eradication by vapor heat treatment without impairment to
fruit quality.
In contribution to solve scientific, practical problems mentioned above, we have
embarked on the subject “Experiments on procedures of vapor heat treatment to control
fruit flies infesting export mango”.
The study aims at: Establishment of vapor heat treatment procedures for control of
mango fruit flies and fruit quality improvement, value enhancement of Vietnam export
mango in support of Vietnam fruit exporters, boosting national foreign exchange earning
and mango growers income.
Mango (Mangifera indica), fruit of medium size, weighing approximately 350g,
having thick flesh (2.7 cm), small seed (11% of the fruit volume); hence significant edible
portion(79%). The top of the fruit, the point of attachment to the peduncle is raised to sharp
point, which perhaps, gives the variety the name of Cat Chu.
Beside the above mentioned desirable features, Cat Chu mango has a pleasant sweet
taste (14 – 20% brix sugar content), with smooth, chewable, flesh and stable high yield.
Cat Chu export destined fruits should be bagged for protection at the orchard when
they attain 2 – 3 cm in size. Those for quarantine experiments should not be sprayed with
pesticide a month before harvest.
The main harvest season starts from early March to late May, at physiologic maturity
stage (vernacularly known as green – ripe) meaning the skin is still green but the flesh close
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to seed has turned yellow in distinction from physiologically immature fruit whose flesh
around the seed still remains whitish. Fruit harvested at the physiological maturity stage
maintains quality at full ripening. Ethylene gas (C2H4) treatment for 1 – 2 days after harvest
only helps to induce uniform ripening and coloration.
According to Peterson et al’s recommendation, Cat Chu Mango picking should start
in the morning and end before14 hours to allow for transport to processing facilities in
daytime. It is best to keep mango at 280C and 70 -75 % RH the first night after harvest.
Bagged fruit that show injury or damage are culled out. Only the intact ones are kept
in original bags and placed in wooden crates or bamboo baskets to minimize injury.
They should be immediately transported to the warehouse or Plant quarantine
processing station. At post – harvest not prevention fungicides are needed furthermore,
treatment with a solution of 1 ml/l Cardazim 500 FL at 52oC in 5 minutes may be applied
within 24 hours after harvest.
Generally speaking, harvest procedures for Cat Chu mango are similar to those
applied to Kensington mango in Australia.
After cutting the fruit stalk, drain out the sap so as not to let it taint the fruit skin,
then sort the fruit by weight and proceed to ripening. Quarantine treatment is applied to
control fruit flies then mango fruits are packed, securely sealed in the solation chamber then
stored in cold room at 10 -13oC or kept in the area awaiting treatment at 28 – 30oC.
Table 1: Production amounts of Mango fruit in Viet Nam in 2010
Production
province
KhanhHoa
Dong Nai
Dong Thap
TienGiang
Total in country
Production area
(ha)
6,491
9,211
9,300
6,612
87,664
Yield
per ha
(tons)
7,9
9,4
7,5
14,7
8,1
Production
tonnage
(tons)
43,871
65,317
61,357
86,530
579,976
Source:SOFRI (2010)
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II. Procedures of vapor heat treatment to control fruit flies infesting export
mango:
LOCATION
Orchard
HARVESTING, PROCESSING AND PACKING
At the mango orchard:
Workers are picking
green fruit from early
morning.
Mangoes
covered by waterproof
paper bags are carried in
net bag to the collection
site.
The first in-situ sorted
out mangoes are put in
deep bottomed plastic
basket for carriage to the
supplier’s warehouse.
Supplier
Motorbike
conveyed
mangoes being still kept
in big net bag.
1
Mangoes brought to
Yasaka Fruit or Good
life factory the next
morning still keep their
paper bag covering and
remain undisturbed in
plastic baskets with
cushioning by their
initial net bagging.
Workers removing fruit
from the net bag for
sorting and cleaning
according to factory
input standard. At this
stage, dirts and insects
are eliminated.
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2
3
4
Post harvest fungicide
treatment together with
hot water dipping at
520C in 2 – 3 minutes.
Sorting of mangoes
before VHT treatment
by
standard
specification.
Putting Mangoes in the
Vapor Heat Treatment
System (VHT) for 20
minutes heat treatment at
fruit core temperature of
470C.
Afterwards
proceeds cooling by
fresh air for 10 minutes
and by fresh water for
20-30 minutes.
Before access to the
packing area, one must
go through the isolation
room fitted with 3 serial
doors, one of which
opens on operation of a
signal
lamps,
red
meaning closure. Each
door has a tightening
seal.
Door 1 and 3 have an air
current blow system to
ward against incidental
insect penetration.
Going through door 1,
workers must change
footwear, wash hands
with soap and dry them
at heat dryers before
accessing the packing
area. This chamber is
equipped with insect
killer lamps.
Going through door 2:
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here
the
external
inspector or customers
are required to change
footwear
before
accessing the packing
area. Here, there are also
insect killer lamps.
Going through door 3:
This is the transition site
between the isolation
room and the packing
area. It is fitted with
signal lamps: red means
closure.
The packing area is
completing isolated from
the outside for no
concommitant
insect
infestation,
periodical
yearly
chemicals
disinfestation sprays are
applied here. The floor is
water washed daily and
sanitation
kept
by
alcohol
swabbing
weekly.
5
An expert checks the
sensors
measuring
temperatures at the fruit
core after removal from
VHT
(treatment
completed).
After removal from
VHT, there is a time
lapse of 30 minutes
before mangoes are fed
to the sorting machine
and packed or put in
cold storage prior to
packing. The ambient
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temperature
190C.
is
about
Mangoes pass through
the sorting machine for
culling out underweight
fruit.
Mangoes laid on the
packing counter made of
stainless steel, which is
cleaned daily after each
packing, and sanitize
weekly with bactericide
alcohol.
This is a kind of
packaging for overseas
market.
The cartons that have
air-holes are plugged
with netting material to
prevent
insect
penetration.
Vietnamese
inspector,
with accreditation by NZ
MAFF, will inspect
mangoes before issuing
phytosanitary certificate
for export permit.
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Cold storage (range: 8 11 degree Celsius) to
ensure longer
fresh
keeping of fruit.
6
This is the fourth door
that provides isolation
between the packing
area and the loading
area. The outside space
is for placement of fruit
before loading.
Inside
7
Loading area is equipped
with 4 insect killer lamps
and 2 air blower sytem
to prevent penetration of
insect.
This area is enclosed by
two doors 4 and 5, only
one of the two is opened
at a time, do not open
both at the same time.
8
Outside the hall is the
front of yard, where
loading is operated.
outside
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Further: PROCESS OF TREATMENT MANGO FRUIT
1. Setting parameters to the treatment machine:
 Mango are treated by VHT machine as follows :
- Time of treatment from 3.50 hrs to 4.50 hrs at a capacity of around 4 -5 tons of fruit.
- 20 min duration at fruit core temperature of 470C and humidity about 90% or more.
- Cooling mango after heat treatment by fresh air in 10 mins, then by fresh water in 20-30 mins.
- Air pressure during heat treatment around 5 bar, hot steam water around 2 bar.
 Setting practices are made as follows:
- Setting temperature of chamber machine at 480C
- Setting humidity of chamber machine: about 90% or more.
- Plastic trays for placement of mango fruits are piled on pallets which will be fed into the
treatment chamber. The door of the chamber is then closed.
-
The sensor is inserted into mango fruit (10 repetitions). The tip of the sensor should reach the
core of the fruit:
+ After sensor insertion, the fruit is put back in the middle of the tray of the top pallet.
2. Heat treatment operation flow chart:
HEATING UP
MAINTENANCE OF
DESIRED HEAT LEVEL
FOR 30 MINUTES
TREATMENT
COMPLETION
COOLING
DRYING
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- Monitoring sensor reading at 430C
- Monitoring sensor reading at 470C, 90% approximate humidity
3. Checking of treament outcome and removal of fruit from the treating chamber:
- For assurance of 470C temperature at 90% humidity sensor reading for 20 minute-duration.
This specification requirement is crucial for Vietnamese expert to monitor and pronounce
effectiveness or non-effectiveness of the treatment.
- Removal of sensor from the control fruit and taking out of pallets from the treatment
chamber for cooling.
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