Controlling rice kernel cracking in the field and post-harvest processes in the Mekong delta
Collaboration for Agriculture and Rural Development (CARD) Program
CONTROLLING RICE KERNEL CRACKING IN THE FIELD AND
POST-HARVEST PROCESSES IN THE MEKONG DELTA
Project title: Investigation of rice kernel cracking and its control in the field and during post-harvest
processes in the Mekong Delta of Vietnam
Project code: CARD 026/05VIE
Authors:
Project implementing organizations:
1 Nong Lam University Ho Chi Minh City, Thu Duc District, HCMC, Viet Nam
2 The University of Queensland, St Lucia, Brisbane QLD 4072, Australia
Vinh Truong1, Tuyen T. Truong1, Bhesh Bhandari2 & Shu Fukai2
SUMMARY
The objectives of CARD project 026/VIE-05 were to improve the quality and value of rice, through an
integrated approach which encompasses farmers, millers, service providers and extension workers
and education institution. From April 2006 to November 2009, this project conducted experiments on
harvesting time and method, flat-bed drying, fluidised-bed drying, and milling performance. It was
found that any delay or longer harvesting time can cause more losses. An optimal harvesting time for
highest head rice yield of some main rice varieties has been proposed by this project. The
performance of flat bed drying was improved for bester rice quality. Fluidised bed drying followed by
tempering above glass transition temperature of rice then tower drying or ventilation was found to be
a potential drying technology for high moisture paddy. The milling is another important factor to
improve the head rice yield. Dehusking using rubber roll will improve HRY in comparison to stone
disc but only when the paddy is dried correctly up to moisture content of 14%.
The systematically data collection and experimental results were prepared for training. There were
total of 2392 farmers and 306 extension workers of Can Tho City and Kien Giang province
participated in the training program. These extension activities had a very satisfactory impact on the
farming practices of smallholder farmers and local extension workers. To build up staff competence,
three NLU staff members undertook the technical training at the University of Queensland. In
addition, a rice testing laboratory was established. An integrated rice management chain model from
harvesting to milling for a better rice quality and higher farmer income was proposed. Under the
circumstances if the advanced system is applied to MRD in rice production, i.e. correct harvesting
time, combined-harvesting cutting, mechanical drying, milling using modified dehusker, MRD may
reduce 13% total losses which are equivalent to USD 190 million per annum.
Two articles extracted from this project were available in Drying Technology and International
Journal of Food Properties. Two research works in association with optimisation of high temperature
fluidised bed drying performance were presented at 6th Asia-Pacific Drying Conference held in
October 2009 at Bangkok.
percentage of rice post- harvest losses in MRD
is approximately 15-20 %. There are many
factors accounting for the post-harvest losses
of rice and occurring as early as pre-harvesting
stage and subsequent periods from harvesting
to storage. Rice grains can be damaged or lost
quantitatively and qualitatively due to the
inappropriate practices during harvesting,
reaping, threshing, sun/mechanical drying,
1.
Introduction
Mekong River Delta (MRD), the largest rice
production region in Viet Nam, is producing
about 50 % of Viet Nam total rice output. This
region has accounted for more than 90 % of
Vietnamese rice export in the past decade with
16 million people or about less than 20 % of
the total population. It is estimated that the
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CARD 026/05 VIE – Control rice cracking kernel
loading/unloading,
transporting,
milling
system can serve as a compact drier. High
temperature drying such as fluidizied bed
drying is able to cope with the drying of large
volume of rice harvested within the short
period of time.
processing and storage conditions. Reduced
whole rice grain yield due to cracking is one of
the major issues that directly reduce income
and availability of staple food to the farmers in
the MRD.
Milling processing is an important stage as
it produces the final product (white rice) in the
chain of post-production of rice. In addition to
the rice grain cracking is potentially occurred
in previous postharvest stage, rice kernels can
be cracked as a result of unsuitable milling
technology applied, i.e., low efficiency of
milling system, low quality of paddy before
undergoing milling. Few research works
pointed out that inappropriate milling system
causes more grain cracking meanwhile there is
no information reported on the effect of paddy
quality on performance of milling system. Due
to the current post-harvest system in the MRD
the mechanical drying can cover only 30% of
the total wet paddy. Most of rice has been
processed by sun drying. In addition, the price
of paddy between 14% and 17-18% moisture is
not differentiated clearly by the traders. Thus,
the farmers prefer to sun-dry the paddy to final
moisture content of 17-18%. A large amount of
high moisture paddy (17-18%) is demanded for
milling. Thus, the milling operators have used
the stone-dehusker for husking of paddy to suit
this high moisture content paddy. This system
has reduced HRY and needed to be
investigated.
The cracking or partial fissuring of rice kernels
may occur right in the paddy field due to
incorrect harvesting time and improper
harvesting practices, and occur also because of
adverse post-harvest drying conditions and
inappropriate milling operations. Weather
conditions at around harvesting period are
different between the wet and dry seasons and
this can impact the rice fissuring and cracking
during milling. It has been shown that
timeliness of harvesting can influence milling
yield significantly. Harvesting rice at crop
maturity can give a maximum head rice yield
(Kester et al. 1963, Bal and Oiha 1975). Any
delay in harvesting time causes reduction of
head rice yield (Bal and Oiha 1975, Ntanos et
al. 1996, Berrio et al. 1989) and extended
delay in harvesting can lead to significant
losses in head rice yield. However, there is no
experimental data available on the impact of
harvesting time on rice cracking and head rice
recovery on the rice varieties grown at
different seasons in the Mekong River Delta.
The occurrence of rice cracking during
postharvest stages causes further reduction in
head rice yield. The quality of rice has become
a central issue for Vietnamese farmers,
particularly for wet-season rice production,
when the moisture content of paddy at harvest
can be as high as 35% wet basis. It is important
to dry rice as quickly as possible after
harvesting to prevent spoilage and maintain
grain quality. Currently, flat bed dryer for
drying paddy is common in MRD with the
installation of about 6500 units as of 2007
thanks to its simple drying technology, low
installation and drying costs, yet rice quality is
acceptable. Improvement of flat bed drying
performance, therefore, is necessary. However,
in milling plants, storage houses, where paddy
have been gathered, paddy drying technique
for large scale and mechanization of
production processes should be considered to
apply. The high temperature fluidized bed
drying technique has been established as an
effective method for drying high moisture rice
grain, which can easily deteriorate in the
tropical humid environment (Soponronnarit et
al. 1994, 1999; Sutherland et al. 1990). The
fluidized bed integrated with a tempering
This project aims to improve the quality
and value of the rice, through an integrated
approach which encompasses farmers, millers,
service providers and extension workers and
education institution as can be summarised in
Figure 1. A key objective of this project is to
improve the knowledge of smallholder farmers
by organizing workshops and demonstration
for farmer cooperatives in the region so that
appropriate harvesting and subsequent grain
handling techniques are observed to improve
rice grain quality. Similarly there will be
demonstration and workshops for small millers
to encourage them to install driers and/or
provide them technical knowledge to practice
optimum drying conditions. Improvement of the
capacity of the extension workers by providing
updated knowledge is another objective. The
theory of grain drying will be advanced that
would improve designs of future dryers. The
education institutions involved in the project
will work together for capacity building of their
staff members in the Nong Lam University.
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Collaboration for Agriculture and Rural Development (CARD) Program
Generate appropriate
harvesting methods to reduce
grain cracking
Increase the research
and teaching
+Provincial ext. centres
+Pilot farmers’ cooperatives
capability
Optimize drying methods
+Workshop/demonstrations/
/training/study tours
+Testing lab build-up
Experiments on fields/in lab
+Supporting instruments
+Learning by doing activities
+Communications
Harvesting/Drying/Milling
+Training staff
members in Australia
+Visiting leading rice
research institution
Correct harvesting time
App harvesting method
Opt flat bed & fluidized bed
drying
the farmers, service
providers, millers and
extension workers aware of
various factors responsible
for harvesting and milling
losses
Senior research projects
Rice testing lab
Training manual
Farmer
survey
Scientific publications
Changes in Knowledge,
Attitudes& Skills
+Integrated business model
+Benefit assessment
Figure 1: Various activities carried out through many pathways in CARD project 026/VIE05
The specific objectives of this project
during the period of 2006-2009 were:
concept, particularly in
temperature compact-drying system.
a
high
1. To identify and generate information for
intervention opportunities in pre-harvest
and during harvest stages of rice
production to reduce grain cracking and
losses. These intervention opportunities
include the correct harvesting time on
cracking portion of various popular rice
cultivars and seasons and the appropriate
rice harvesting method (manual or
mechanical).
3. To collect milling system data and carry
out milling experiments for medium and
large capacities of 1 ton/hour and 7
ton/hour, respectively.
4. To investigate changes in physico-
chemical properties, milling quality and
physical strength of rice due to high
temperature compact-drying system and
to validate molecular relaxation concept
during post-drying annealing and
subsequent storage of rice.
2. To improve the performance of current
driers applied in MRD to minimise the
level of rice cracking and optimise the
drying method on the basis of
5. To organise training workshops and
demonstrations for the farmers and
extension workers on the economic value
of correct harvesting time, appropriate
fundamental
structural
relaxation
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CARD 026/05 VIE – Control rice cracking kernel
harvesting method, and the benefit of
mechanical drying against sun drying.
actual harvesting losses due to current
harvesting practice by farmers were collected
in Can Tho and Kien Giang provinces.
6. To make the farmers, service providers,
millers and extension workers aware of
various factors responsible for harvesting
and milling losses and degradation of rice
quality.
2.2 To improve the performance of
current driers applied in MRD to
minimise the level of rice cracking
and optimise the drying method on
the basis of fundamental structural
relaxation concept, particularly in a
high temperature compact-drying
system
7. To increase the research and teaching
capabilities of institution and staff
members on rice quality and related
products.
8. To build a concept of integrated rice
management model.
2.2.1 Flat-bed drying
Experiments on performance evaluation of
current dryers used in MRD were conducted by
the NLU Center for Agricultural Energy and
Machinery (CAEM). To test the drying
performance of flat bed drier in the actual
production condition, two of 8-ton flat bed
driers were installed in Tan Thoi 1 cooperative
(Can Tho City) in September 2007 and Tan
Phat A (Kien Giang province). Experiments
were undertaken on both 8-ton flat bed driers
to characterise the driers in order to determine
the optimum drying conditions. In January
2007, one solar assisted 4-ton flat bed drier
was also installed in Go Gon cooperative
located in Long An Province. In addition to
above dryers installed in cooperatives, another
one-ton lab scale flat bed dryer was
constructed at NLU. These dryers were also
used for both experiments and training
purposes. The available data was incorporated
into the training manuals.
9. To evaluate the impact of the project.
10. To disseminate the results of this project
in international journals and conferences.
2.
Research contents and methods
2.1 To identify and generate information
for intervention opportunities in pre-
harvest and during harvest stages of
rice production to reduce grain
cracking and losses
Experiments were carried out at three
locations, namely Seed Centre (An Giang
Province), Tan Phat A Cooperative (Kien
Giang Province) and Tan Thoi 1 Cooperative
(Can Tho City) in four consecutive harvesting
seasons during two years (2006-2008). Before
conducting experiment, baseline information
of current farming practices was collected.
Field experiments on correct harvesting time
were then carried out on some most cultivated
rice varieties such as OM1490, IR50404,
OM2718 of Tan Thoi 1 (Can Tho) and
OM2517, OM4498, IR50404, AG24 of Tan
Phat A cooperative (Kien Giang) throughout
wet (June to August 2007) and dry (March
2008) seasons. Level of rice cracking for both
brown and milled rice samples and head rice
yield were measured. The effect of harvesting
time around maturity on grain cracking and
head rice yield was then evaluated.
2.2.2 Tower drying
Tower drying in Long An Province was
also used to evaluate its performances (drying
capacity, drying temperature, rice husk
consumption, and electric power consumption),
drying technique (final moisture differential,
grain crack and head rice recovery) and
economic
aspect
(labour
requirement,
investment and drying cost).
2.2.3 Optimization of the drying method
based on glass relaxation phenomenon
Harvesting method (manual and harvester)
comparison on the post-harvest losses during
spring/dry harvesting season was also
undertaken in Kien Giang, Can Tho and Long
An provinces. Cracking behaviour of the grain
due to threshing was also investigated in Can
Tho and Kien Giang provinces. Data of the
Figure 2a and 2b present the structural
relaxation concept during rice drying and
tempering applied in this project.
133
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
Moisture gradients
Moisture gradients
DRYING
TEMPERING
COOLING
MC
Temperature,
0C
High drying
temperature
Rubbery region
Moisture
readsorption
Low drying
temperature
Glassy region
Glassy state
Rubbery state
me
Time
Figure 2a: Pictorial representation of hypothetical state of the rice kernel undergoing drying, tempering
and cooling when glass-rubber transition concept applied to its state changes (more explanation is attached
in research report)
C
A
Enthalpy
H(Ta,0)
D
B
H'(Ta,ta)
C'
I'
M
H'(Ta)
H'e(Tf)
Y
X
slope1
I''
He(Tf0)
I
slope2
Temperature
Tf0
Ta
Tf
Figure 2b. Hypothetical diagram to describe the enthalpy change in material glasses for unaged sample (path
AIXIA) and aged samples at temperature above Tg (path BC’I”XI”D for the enthalpy monitored by DSC, path
BCMYI’A for the actual enthalpy). The gain of enthalpy (path BC) increases the fictive temperature of system
from Tfo to Tf after aging time ta (more explanation is attached in research report)
which was purchased through this CARD
A high temperature batch fluidised bed lab-
project.
scale dryer (HPFD150) with a tempering
system was developed at the Chemical
Engineering Department of Nong Lam
University. This drier was used to determine
the effect of high temperature tempering on the
head rice yield, rice cracking level and
mechanical strength of rice. The mechanical
strength of individual kernel of rice was
measured using a Texture Analyser TA-XT2
2.3 To collect milling system data and to
carry out milling experiments for
medium and large capacities of 1
ton/hour and 7 ton/hour, respectively.
Data collection of current milling systems
were undertaken in two provinces from many
milling plants in each province (Kien Giang
and Tien Giang) in 2007-2008. This work
assumed that the head rice recovery will not
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CARD 026/05 VIE – Control rice cracking kernel
only depend on the initial rice quality (existing
cracks or weaker grain), but also on the
efficiency of the milling operation. Therefore,
in this work, actual milling loss data were
collected in these two provinces. After
the level of rice kernel fissuring, mechanical
strength and head rice yield of three Australian
grown rice varieties, namely Kyeema (long-
grain), Amaroo and Reiziq (medium-grain).
Paddy samples were dried at 40, 60, and 80oC
and then tempered for 0, 40, 80 and 120 min.
The dried rice samples were then stored up to
four months at 4, 20 and 38 oC. The
investigation of post-drying annealing effect at
above and below glass transition temperature
of rice on mechanical strength and its
association with the level of kernel fissuring
and milling quality was expected to provide
additional valuable insight to understand the
rice cracking behaviour.
conducting
data
collection,
milling
experiments were designed to investigate
milling efficiency and effects of rice moisture
content on milling performance of different
milling systems.
2.3.1 1-ton milling system
The first milling experiment was carried out
with 1-ton milling system (RS10P – SINCO)
at Can Tho province. The purpose of this
experiment was to determine the effect of
paddy moisture content on the HRY while
using rubber-roll dehusker. The paddy variety
was OM1490 and paddy samples with three
moisture levels (14, 15 and 16%) were
compared.
2.5 To organise training workshops and
demonstrations for the farmers and
extension workers on the economic
value of correct harvesting time,
appropriate harvesting method, and the
benefit of mechanical drying against
sun drying
2.3.2 7-ton milling system
The second experiment was carried out
with 7-ton milling system for two varieties
(OM6561 and IR50404) at two moisture levels
(14% and 17-18%) using two milling
techniques, i.e., stone and rubber roll
dehusking. Currently, in MRD, 60% and 40%
of paddy are processed by stone and rubber
roll dehusking, respectively. The modified
milling technique processes 0-30% and 70-
100% of paddy by stone and rubber roll
dehusking, respectively. In this experiment, the
modified milling system with 30% husking by
stone dehusker and 70% husking by rubber-roll
dehusker is called modified 70% rubber-roll
dehusker and denoted by M70RD. Similarly,
the modified system with 100% rubber-roll
husking is denoted by M100RD. The traditional
system is therefore denoted by M30RD (only
30% of paddy processed by rubber-roll
dehusker). The Hung Loi milling plant at Tan
Hiep district, Kien Giang province was used
for this experiment.
As a key objective of this CARD project, the
demonstrations and training activities for the
extension workers and the farmers were
undertaken from February 2007 to June 2009
in six districts of Kien Giang Province (Giong
Rieng, Chau Thanh, Tan Hiep, Hon Dat, An
Bien, Go Quao) and five districts of Can Tho
City (Vinh Thanh, Thot Not, Phong Dien, Co
Do, O Mon). The content of training session
comprised of three lessons on harvesting time,
harvesting method and drying technique and
demonstrations of the dryer and the combined
harvester. Participants visited the dryer in local
sites and discussions were held afterwards.
Every training session was finished up by
related discussions.
2.6 To make the farmers, service providers,
millers and extension workers aware of
various
factors
responsible
for
harvesting and milling losses and
degradation of rice quality
A workshop ‘Current situation of milling
system in the Mekong River Delta and methods
to improve the milling quality of rice’ was
organized on 6th Dec 2008 at Tan Hiep
District, Kien Giang Province. This workshop
emphasized on current situation of the milling
system in Kien Giang Province based on
results of survey conducted during two years
(2006-2008), introducing various milling lines
and equipments, and evaluating the investment
efficiency, industrialization planning of milling
system in MRD. Participants including milling
2.4 To investigate changes in physico-
chemical properties, milling quality and
physical strength of rice due to high
temperature compact-drying system and
to validate molecular relaxation concept
during post-drying annealing and
subsequent storage of rice
This research work was undertaken in The
University of Queensland. This experiment
investigated the effect of drying temperatures,
tempering regimes and storage conditions on
135
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
plant owners, service providers, extension staff
and Nong Lam University presented and
discussed current situation of the milling
system in MRD, particularly at Tan Hiep
district which possesses a large number of
milling units in Kien Giang Province.
Farmers do not have resource to purchase the
rice harvesting, drying or milling equipments.
Only the service providers can invest
harvesters, dryers and milling equipments. As
these techniques improve, benefit goes to the
service providers rather than the farmers. This
is because of the fact that the service providers
control the price of wet and dried rice in
addition to the service fee. For the farmers to
gain the benefits from reduction of losses due
to advanced harvest and post-harvest
technologies, the farmers should possess the
white rice. A model so-called “integrated rice
management chain model” from harvesting to
milling for a better rice quality and higher
farmer income may help the farmers to possess
the white rice, .i.e., gain the benefits from
reduction of losses. The purpose of
management model of rice is to bring the
benefit to the farmers from the advantages of
post-harvest technologies.
2.7 To increase the research and teaching
capability of institution and staff
members on rice quality and related
products
2.7.1 Rice testing lab build-up
A laboratory is equipped with analytic
instruments purchased from CARD fund and
refurbishment cost from NLU. All the pieces
of equipment include various rice dryers, pilot
milling system, incubator, texture analyser etc.
purchased from CARD fund are located in this
laboratory. This rice analysis laboratory was
not only used for testing of thousands of rice
samples from CARD-based research but also
served as research site of many studies in
relation to rice quality and food texture by a
number of NLU staff members and senior
students.
2.9 To evaluate the impact of the project
Farmer survey was carried out in Tan Phat A
cooperative, Tan Hiep district, Kien Giang
province in early March 2009. The objective of
this survey is to determine the likely impact of
CARD 026/VIE-05 since the project started in
September 2006. Thirty-one specific questions
containing knowledge, attitude and practice
questions were designed to address at various
aspects of the project activities. The project
team believed that survey research could help
clarifying the benefits, effectiveness and
weakness of this project during the last three
years. A total number of respondents for this
survey in dry season 2009 were 162.
2.7.2 Training staff members in Australia
During the implementation of this CARD
project, three staff members of NLU were
trained for three-month period in the
University of Queensland, Australia. These
NLU staff members learned advanced
analytical techniques for rice quality
determination through undertaking of research
projects. In addition, there also was a NLU-
based staff AusAID-supported student doing
Master by research program working in this
project.
2.10 To disseminate the results of this project
2.7.3 Visits of project leader/coordinators
in
international
journals
and
At the early stage of this CARD project,
Vietnamese project leader and Australian
project coordinators visited some rice research
institutes in Southeast Asian countries. This
observation tour took place in King Mongkut’s
conferences
Thanks to the abundant activities of this
project from the field to the laboratory. The
results obtained are not only useful for
stakeholders but also give
a
better
University
of
Technology
(KMUTT),
understanding on rice post-harvest processing
from scientific point of view. Some selected
results were structured in the format of
scientific papers and submitted to international
journal such as Drying Technology,
International Journal of Food Properties and
Conferences, namely 'Post Harvest 2009 –
Rice Exhibition and Conference’ to be held in
July 2009 in Bangkok and the 6th Asia-Pacific
Drying Conference to be held also in Bangkok
in October 2009.
Thonburi, Bangkok and IRRI, Philippines in
October 2006. Information was gathered from
those institutes with regard to rice drying, post-
harvest handling, farmers’ training and milling
assisting project planning, experimental design
and up to date rice analysis methods in leading
rice research institutions.
2.8 To build a concept of integrated rice
management model
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CARD 026/05 VIE – Control rice cracking kernel
difference in head rice yield (P<0.05) between
treatments, assuming all samples were milled
in the same condition. For example, optimum
harvesting timeliness in order to reduce grain
losses due to rice cracking is recorded as 86,
88, and 86 days for OM 2517, IR50404, and
AG24, respectively. Table 1 and 2 are a
summary of optimum harvesting time for 7
varieties undertaken by this project in rainy
and dry seasons starting from June 2006 to
March 2008. In general, the optimum
harvesting time of the rainy season is longer
than that of the dry season. The results further
confirmed that harvesting time has an
influence on rice cracking. Early harvesting
results in lower percentage of rice cracking and
higher head rice yield. Though variations in
rice cracking and head rice yield were
observed between rice varieties and crop
seasons, the similar trend in all the cases
demonstrated that correct harvesting time is a
key intervention opportunity to reduce grain
losses.
3.
Research results and discussions
3.1 Influence of harvesting time around
grain maturity and harvesting methods
on rice cracking and head rice yield in
the Mekong River Delta of Vietnam
3.1.1 Harvesting time
Timely harvesting plays an important role in
controlling rice cracking. Reduced whole rice
grain yield due to cracking causes the value
loss and reduces the farmers’ income. The
results showed that the rice cracking was
strongly influenced by both the variety and
time of harvesting around maturity. Actual
data collected in Tan Phat A cooperative, Kien
Giang in dry season 2008 indicated that
delayed harvesting increases the level of grain
cracking substantially in all three rice varieties
OM2517, IR50404, AG24. Percentage of rice
cracking went up when rice was harvested later
than expected harvesting day of farmers,
particularly at +6 days treatment. For each
investigated rice variety, there is significant
Table 1. Optimal harvesting time for highest HRY (coloured numbers are the optimal growing time for
harvesting)
Variety
Season
Rainy
Time
Growing time (day)
June 06
90
90
90
90
88
84
84
88
89
96
88
88
90
90
92
92
92
92
90
86
86
90
91
98
90
90
92
92
94
94
94
94
92
88
88
92
93
100
92
92
94
94
96
98
96
96
94
90
90
94
95
102
94
94
96
96
98
104
98
98
96
92
92
96
97
104
96
96
98
98
88
88
88
88
86
82
82
86
87
94
86
86
88
88
OM1490
Feb 07
June 06
Feb 07
July 07
Feb 07
Mar 08
July 07
Feb 07
July 06
July 06
Mar 08
June 07
Mar 08
Dry
Rainy
Dry
OM2718
OM2517
Rainy
Dry
Dry
Rainy
Dry
OM4498
Jasmine
AG 24
Rainy
Rainy
Dry
Rainy
Dry
IR50404
137
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
Table 2. Seasonal trend of effect of harvesting time before and after maturity (4-6 days prior and 4-6 days
later than the expected day of maturity) on the proportion of cracked grains (prior to milling) and head rice
recovery†
Crop
season
Rice
variety
Proportion of cracked grain
%
Relative head rice yield %
Opt.
harvestin
g date
Before maturity
After
Before maturity
After
maturity
maturity
OM1490
OM2718
OM2517
OM4498
AG24
0.8-9.6
0.4-1.2
3.5-15.7
2.5-3.9
0.3-1.5
1.1-1.5
4.0-4.5
0.5-2.3
0.7-6.3
0.7-3.6
1.1-3.7
6.5-16.4
0.8-2.8
1.1-23.6
4.0-10.8
12.1-20.3
8.1-10.4
1.1-4.1
101-109
103-117
90-114
91-93
72-88
84-93
94
92
94
94
94
90
98
92
92
86
91
88
88
Wet
105-117
96-108
83-108
99-106
87-99
93-97
IR50404
Jasmine
OM1490
OM2718
OM2517
OM4498
AG24
0.4-1.3
103-105
75-99
6.0-7.7
5.6-22.4
3.2-8.5
93-99
83-95
Dry
98-101
77-106
75-93
92-98
9.3-60.5
1.1-9.3
51-97
90-98
21.5-53.1
133-145
86-102
86-95
IR50404
1.7-12.3
105-107
†Head rice yield is expressed as relative to the yield on maturity day.
harvesting time, and hence greater harvest
losses. Thus, shattering loss due to harvesting
method and also due to time of harvesting
(particularly late harvesting) is an important
factor to consider for reduction in the grain
losses during harvesting. In addition, manual
harvesting results in higher scattering losses in
comparison to machine harvesting. Machine
harvesting is beneficial in terms of quick
harvesting of the crop and hence in terms of
minimizing harvesting losses.
3.1.2 Harvesting methods
Harvesting losses consist of shattering and
threshing losses. Table
3
shows each
component and total harvesting losses. The
total harvesting losses can be as high as 4.4%.
A threshing loss of 1.0% for combine harvester
was estimated by the manufacturer. On an
average, mechanical harvesting reduces
harvesting losses. Due to longer time required
for harvesting, it is likely that manual
harvesting will result in greater delay in
Table 3. Effect of harvesting methods on the harvesting losses
Shattering Threshing Harvesting
Harvesting method
losses (%) losses (%)
losses (%)
2.6-4.4
2.4-4.2
1.8
Hand and heaped immediately
1.4
Hand
1.2-3.0
1.2
Hand and dried in the sun (one day)
Reaper and heaped immediately
Reaper and dried in the sun (one day)
1.1
Reaper
0.7
0.8
1.5
Combined
harvester
1.3-1.5
1.0
2.3-2.5
138
Collaboration for Agriculture and Rural Development (CARD) Program
indicate that the grain cracking is not
The threshing method applied can cause the
cracking in the rice kernels and eventually
reduce the head rice recovery. The data
collected in two provinces in Mekong Delta at
the same time when experiments were
conducted are presented in Table 4. The results
significantly affected by the method of
threshing. However, some reduction of head
rice recovery was observed in the case of rice
threshed by machine.
Table 4: Effect of threshing method on rice cracking and head rice recovery
Rice varieties
Grain cracking (%)
Brown rice White rice
Head rice
recovery
(%)
Hand
Machine
3.9
Hand
Machine
1.8
Hand Machine
OM2718/ OM
1490
4.1
3.0
49.9
46.7
An Giang 24
0.9
2.4
1.5
0.7
45.6
44.0
economic potential. Major findings from the
survey on the current status on the use of flat-
bed dryers in 7 Provinces were: the trend for
increased drying capacity, the role of local
manufacturers and local extension workers,
government support with interest reduction for
dryer loans, the drying during the dry-season
harvest, and especially the unbalance between
drying costs and drying benefits.
3.2 Rice drying on the basis of
fundamental structural relaxation
concept
3.2.1 Flat bed drying
Mechanical drying not only reduces grain
losses caused by germination and spoilage but
also be an utmost intervention opportunity to
minimize rice grain cracking after drying or
during milling stage. The study, including
experiments and survey on the flat-bed dryer,
focused on the cracking of paddy grains, and
on comparing the air reversal mode. Results
showed that, in both the 8-ton production-scale
dryer and the 20-kg laboratory dryer, the effect
of air reversal was very apparent in reducing
the final moisture differential; however, its
effect on the drying time or the drying rate was
not statistically significant. Mechanical drying,
whether with or without air reversal, was
superior to sun drying in terms of reducing rice
crack. However, compared to shade control
drying, drying (with or without air reversal)
did decrease the head rice recovery and
increase the crack; the causing factor was not
apparent, most suspected reason was the
3.2.2 Tower drying
Testing the performance of one tower dryer
which had been installed in Long An Province.
The grain crack was satisfactory in batches
o
with a drying temperature lower than 55 C
and a drying rate of about 0.5 % /hr. On the
economic side, however, the drying cost three
times higher than that of the flat-bed dryer is
not inducing to its adoption in the context of
current labor and paddy prices.
3.2.3 Fluidized bed drying
The effects of high temperature fluidised bed
drying and tempering on level of rice cracking,
mechanical strength, head rice yield and color
on two rice varieties (OM2717, A10) were
investigated. Rice samples were fluidized bed
o
o
drying rate.
The decrease in head rice
dried at 80 C and 90 C for 2.5 and 3.0 min,
then tempered at 75 oC and 86 oC for up to 1 h,
followed by final drying to below 14%
recovery was inconsistent, slightly lower or
higher in each specific pair of experiments
with and without air reversal; this was not
expected in line with data on the final moisture
differential. Testing of a 4-ton dryer at Long-
An equipped with the solar collector as
supplementary heat source resulted with good
grain quality and confirmed the good
o
moisture (wet basis) at 35 C by thin layer
drying method. For both rice varieties, the
tempering step significantly reduced the level
of kernel fissuring and improved the head rice
yield. The color of milled rice was
significantly (P<0.05) affected by high
139
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
temperature fluidized bed drying, but the
absolute change in the value was very small.
The actual drying time involved with the use
of flat bed driers ranges from 8-10 hrs for wet
paddy, if farmers want to reduce the grain
moisture content to a safe level (14% wet
basis). If the paddy needs to be dried to 15-16
% moisture, the fluidized bed drying system
can be used as a compact drier. The fluidized
bed drying technique evaluated in this study is
strongly recommended for drying paddy in
Vietnam during the wet season to maintain rice
quality as the use of this drying technique was
shown to have an especially beneficial effect
on head rice yield.
influencing the sensory perception of fluidized
bed dried rice, particularly the whiteness.
3.3 Milling experiments for medium and
large capacities of 1 ton/hour and 7
ton/hour
3.3.1 Milling systems
The data collection of milling losses in two
provinces from more than three milling plants
in each province (Kien Giang and Tien Giang)
was undertaken in 2007-2008. The results are
presented in Table 5. The real data and data
collected by survey were quite coherent. Both
data suggested that the head rice recovery in
small scale mills was the lowest and was as
low as 33%. Large rice mills had the highest of
55% head rice recovery. In the actual ideal
condition the head rice recovery and total rice
recovery should be around 59% and 69%,
respectively (as rice is comprised of around
10% bran and 20% husk). In literatures, the
head rice recovery and total rice recovery have
been achieved as high as 60% and 70%.
Therefore, there is still a scope of improving
the head rice recovery even in large scale
mills, let alone a poor performer small scale
rice mills. The importance of improving the
quality of rice can be substantial. As for
example, in Kien Giang province, out of 715
rice mills, 67.6% are small, 28.1% medium
scale and 4.3% large scale mills. Similarly in
Tien Giang province there are more than 900
small household mills.
3.2.4 Optimisation of the multi pass mode
fluidized bed drying method
High temperature fluidized bed drying (FBD)
performance on Vietnamese rice varieties was
optimized by using Response Surface Method
(RSM) with responses were milling quality,
mechanical strength and level of gelatinization.
Optimum drying conditions that maximized
the head rice yield were selected. This
included pass 1 FBD at 83oC for 2.5 min
subsequently tempering at grain temperature
for 40 minutes, pass 2 FBD at 57oC for 4.9
min, and then pass 3 tray drying at 35oC for 4.4
h for IR50404 rice variety, denoted by OP1.
Similarly, Jasmine rice variety should be pass
1 at 87oC for 2.5min, pass 2 at 57oC for 4.9
min and then pass 3 at 35oC for 3.2 h, denoted
by OP2. The gelatinization index (GI %) was
in range of 0.4 – 1.7 %, the hardness of rice
kernels dried in multi-pass fluidized bed
drying was of values 16 – 40 N. The optimum
drying conditions were compared with two-
stage drying including FBD at 80oC for 2.5min
subsequently tray drying at 35oC for 8 h (C1)
or tray drying at 40oC for 5.5 h (C2). The
controlled sample was tray drying at 35oC for
16h denoted by Ref. The results showed that
the HRYs were not significantly different
(P>0.05) between OP1, OP2, C1, C2 and Ref.
The sensory evaluation of cooked rice revealed
that higher fluidized bed drying temperatures,
lower sensory evaluation scores were. This can
be explained by the occurrence of partial
gelatinization during fluidized bed drying
Simple facilities, product mainly supplied for
local demand, not for
a
commercial
production, are the main causes leading to low
rice recovery in a small scale factory. By
proper awareness, training of operators and
maintance of mills the head rice recovery can
be substantially improved. In Tien Giang
province, the surveying data also found that in
the area where the paddy was milled at high
moisture content, 16-18%, had a lower head
rice yield than the area where the moisture of
the paddy is at 14-15% moisture. In Kien
Giang province, the survey results also
suggested that the rice mills using rubber roll
huller had a better head rice recovery than
those using stone disc huller or coffee grain
huller (Table 6).
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CARD 026/05 VIE – Control rice cracking kernel
Table 5: Head rice yield data surveyed in Kien Giang and Tien Giang Provinces
Grain moisture
(%)
Broken rice
(%)
Scale of milling
plant
Average head rice
recovery (%)
Small
Medium
Large
16
16
16
47-48
50-52
52-55
18-22
17-18
16-17
Table 6: Head rice yield (%) as a function of dehulling systems in Kien Giang Province
Stone Disc
huller
Rubber
roll huller
Combined
(Stone+rubber)
49
Coffee grain
huller
Scale of milling
plant
Small
Medium
Large
47
50
-
51
54
-
43
-
53
55
-
denoted by M30RD (only 30% of paddy
processed by rubber-roll dehusker).
3.3.2 1-ton milling system
The purpose of this experiment was to
determine the effect of paddy moisture content
on the HRY while using rubber-roll dehusker.
The paddy variety was OM1490 and paddy
samples with three moisture levels (14, 15 and
16%) were compared. It was found that HRY
was not significantly different between 14%
and 15% paddy moisture contents. However,
when the moisture content of paddy increased
to 16%, the HRY reduced significantly from
46.7% to 37%. This reduction is quite high and
implies the importance of moisture content
level regarding milling performance.
The first experiment carried out in March 2009
showed that regarding moisture content of
paddy of 17-18%, the recovery of rice
containing 15% broken rice (it is called “rice
grade 15”) for M70RD system was 2.44%
higher than that from M30RD system. For the
same M70RD system, the recovery of (rice
grade 15) was 3.25% higher at 14.5% moisture
than at 17-18% moisture. The above results
indicated that M70RD system for rice moisture
of 14% improved the HRY of the rice.
The second experiment was undertaken in
August 2009. As can be seen in Table 7, for
sun drying rice (moisture 17%), HRY of 70%
stone dehusker (M30RD) was higher than that
of 30% stone dehusker (40,71% - 35,89%). For
mechanical drying rice (moisture 14-15%),
HRY of 70% stone dehusker (M30RD) was
lower than that of 30% stone dehusker
(49,28% - 53,36%). HRY of mechanical
drying rice was higher than that of sun drying
rice about 13-14%. Therefore, dehusking using
rubber roll will improve HRY only when the
paddy is dried correctly up to moisture content
of 14-15%.
3.3.3 7-ton milling system
The second experiment was carried out with 7-
ton milling system for two varieties (OM6561
and IR50404) at two moisture levels (14% and
17-18%) using two milling techniques, i.e.,
stone and rubber roll dehusking. In this
experiment, M70RD stands for the modified
milling system with 30% husking by stone
dehusker and 70% husking by rubber-roll
dehusker. Similarly, the modified system with
100% rubber-roll husking is denoted by
M100RD. The traditional system is therefore
141
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
Table 7. Total recovery and head rice yield (HRY)
Brown
rice
White
rice
No
1
2
3
4
70 % SD† + 30% RD†† (sun drying) (M30RD)
30 % SD + 70% RD (sun drying) (M70RD)
30 % SD + 70% RD (Dryer) (M70RD)
70 % SD + 30% RD (Dryer) (M30RD)
82,66% 40,71%
84,53% 35,89%
86,43% 53,36%
85,00% 49,28%
†SD: stone dehusker; ††RD: rubber-roll dehusker
be softer due to the alteration in the pasting
properties. The microstructure and cracking of
cross-sectional areas of rice kernels thin layer
dried at 35oC for 16 h and the fissures existed
between and inside endosperm cells can be
seen in Figure 3a. Figure 3b depicts the
microstructure of rice kernels subjected to the
most severe heating conditions used in this
study (drying/tempering regime: 90oC for 3
min/86oC for 60 min) at different
magnifications. It is hypothesized that the gel
network created during gelatinization can heal
the fissures within the rice kernel by filling the
void between adjacent fissure traces.
Consequently, kernel integrity may be
improved through a partial gelatinization
process resulting in higher head rice yield.
3.4 Changes in physico-chemical
properties of rice due to high
temperature fluidised bed drying and
tempering
The analysis conducted in The University of
Queensland on A10 rice samples showed that
the occurrence of partial gelatinization mainly
on the grain surface during high temperature
drying and tempering altered some of the
physicochemical properties and microstructure
of high temperature fluidized bed dried rice.
As the rice becomes harder and stiffer due to
partial surface gelatinisation, it may require a
longer cooking time when compared with
conventionally dried rice. However, the texture
of the rice tempered for a prolonged time, can
(a)
(b)
Figure 3: (a) Cracks between endosperm cells observed in thin-layer A10 rice kernels;
(b) The microstructure of cross-sections of fluidized bed dried rice kernels.
duration 80-120 min. During the storage period
of up to four months at 4, 20 and 38 C, all
3.5 Changes in cracking behavior and
milling quality due to post-drying
annealing and subsequent storage
o
measured parameters, such as percentage of
fissured kernels, hardness, stiffness, head rice
yield, pasting properties showed the similar
increasing trends. A rapid change in these
physical properties of all rice samples were
observed during the storage at 38oC. A
significant increase in the stiffness values of
rice during storage suggested an existence of
physical ageing during storage of rice below its
glass transition temperature.
This study investigated the effect of drying
temperatures, tempering regimes and storage
conditions on the level of rice kernel fissuring,
mechanical strength and head rice yield of
three Australian grown rice varieties, namely
Kyeema (long-grain), Amaroo and Reiziq
(medium-grain). It was found that tempering
(at a constant moisture level) did not improve
the head rice yield even though the rice kernel
stiffness increased and amount of fissured
kernels reduced with prolonged tempering
The results in this study demonstrated another
important role of annealing process which also
142
CARD 026/05 VIE – Control rice cracking kernel
has an effect on cracking behaviour,
mechanical strength and milling quality of rice
kernels. The relaxation of the molecular
structure within rice starch results in the
densification of the internal structure of rice
kernels that making the kernels then being
strong enough to withstand breakage during
subsequent milling. This study also enhanced
the understanding of rice ageing during storage
in relation to changes in rice fissuring,
mechanical properties and pasting properties.
Rice kernels continued to fissure during
storage for 2 to 3 months, surprisingly without
adversely affecting head rice yield. The
increase in head rice yield during storage,
regardless of an increasing amount of fissured
kernels, implies that the physical integrity of
the rice kernels was strong enough to resist
cracking during milling.
3.6 Extension service
As a key objective of this CARD project, the
demonstrations and training activities for the
extension workers and the farmers were
undertaken during consecutive crop seasons
2007-2009 in Kien Giang Province and Can
Tho City. These training workshops and
demonstrations aimed at disseminating the
farmers and extension workers the economic
value of correct harvesting time, appropriate
harvesting method, and the benefit of
mechanical drying against sun drying. Table 8
summarises the number of training sessions
and number of trained farmers and extension
workers conducted by this CARD project.
Table 8. Number of farmers and extension workers trained in different seasons
from Feb 2007 to July 2008
Province
District
Date
Number of farmers
trained
Number of
officers/extension
workers
One day
Total
313
One day
Total
1. Kien Giang
(Dry season)
1. Kien Giang
Tan Hiep
Giong Rieng
Chau Thanh
Hon Dat
25/02/2007
26/02/2007
28/7/2007
29/7/2007
22/9/2007
23/9/2007
29/9/2007
30/9/2007
08/3/2008
09/3/2008
10/3/2008
11/3/2008
12/07/2008
13/07/2008
23/07/2008
24/07/2008
25/07/2008
19/6/2009
124
189
181
178
195
139
165
167
183
159
135
183
82
10
15
10
12
12
12
15
18
10
11
10
10
13
07
15
20
100
6
25
2. Can Tho
Phong Dien
Co Do
(Wet season)
Thot Not
Vinh Thanh
An Bien
1025
79
1. Kien Giang
(Dry season)
2. Can Tho
Go Quao
O Mon
Co Do
660
158
41
20
1. Kien Giang
(Wet season)
2. Can Tho
Giong Rieng
Chau Thanh
Vinh Thanh
Thot Not
76
81
(Wet season)
75
Can Tho City
Vinh Thanh
0
156
80
135
6
Can Tho (wet
season)
80
Total:
2392
306
143
Collaboration for Agriculture and Rural Development (CARD) Program
Committee Tan Hiep District, Kien Giang
Province.
There were 16 one-day training sessions for
smallholder farmers and a workshop was
arranged in Can Tho City for only extension
workers (25 July 2008). Up to date, a total
number of 2392 farmers and 306 extension
officers have been trained on cracking issues
for controlling of rice quality during harvest
and post-harvest operations. It is clear that the
target of training 1800 farmers and extension
workers in this project (520 farmers/year and
39 extension officers/year) has been quite
achieved. The study tours were also organised
as a part of the training program. About 70
milling plant owners and milling service
3.7 Integrated data on harvest and post-
harvest losses of rice and information
on the use of harvesters and dryers
From the experiments and surveys undertaken
under the project CARD026/VIE05, the data
presented in Table 9 show the average grain
and value losses at each step of the whole
process from harvesting to milling. By the
application of new technologies such as
combine-harvester, mechanical dryer and
modified milling system, the total losses of
rice can be reduced dramatically as analysed.
As can be seen in Table 9, there are 28
possibly matching lines of which conventional
methods are maintained or innovative methods
are applied in one step or the whole process
from harvesting to milling stages.
provider,
machinery
companies’
representatives took part in a milling workshop
‘Current situation of milling system in the
Mekong River Delta and methods to improve
the milling quality of rice’ to be held on 6th
Dec 2008 at the Meeting Hall of People’s
Table 9. Overall evaluation of total harvest and post – harvest losses (converted into grain losses – kg/100
kg dried paddy)
Harvesting
time
Harvesting
method
Total
losses (%)
Threshing
Sun drying
Drying
Milling
Line
Panicle(VL=8.7%)
Yard(VL=4%)
13.1
8.4
1
2
Manual/
Reaper
(GL=2.9%)
Yes
(VL=1.5%)
Correct(0%)
4.4
3
Improved
system
(0%)
Correct
(VL=0%)
Incorrect
(VL=5%)
9.4
4
Yard(VL=4%)
6.7
5
Combine-
Harvester
No
Correct(0%)
2.7
6
(GL=1.2%
VL = 1.5%)
(0%)
Incorrect
(VL=5%)
7.9
7
Panicle(V=8.7%)
Yard(VL=4%)
20.6
15.9
11.9
16.9
14.2
10.2
15.2
8
9
Manual/
Reaper
(GL=2.9%)
Yes
(VL=1.5%)
Correct(0%)
10
11
12
13
14
Normal
system
(4%)
Late
(VL=3.5%)
Incorrect
(VL=5%)
Yard(VL=4%)
Combine-
Harvester
(GL=1.2%
VL = 1.5%)
No
(0%)
Correct(0%)
Incorrect
(VL=5%)
Note: VL= Value losses, GL= Grain losses.
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CARD 026/05 VIE – Control rice cracking kernel
Harvesting Harvesting
Total Line
(%)
Threshing
Sun drying
Drying
Milling
time
method
Panicle(VL=8.7%)
Yard(VL=4%)
17.1
12.4
8.4
13.4
10.7
6.7
15
16
17
18
19
20
21
Manual/
Reaper
(GL=2.9%)
Yes
(V=1.5%)
Correct(0%)
Incorrect (V=5%)
Normal
system
(4%)
Correct
(VL=0%)
Combined-
Harvester
(GL=1.2%
VL =
Yard(VL=4%)
Correct(0%)
Incorrect (V=5%)
No
(0%)
11.9
1.5%)
Panicle(VL=8.7%)
Yard(VL=4%)
16.6
11.9
7.9
22
23
24
25
Manual/
Reaper
(G=2.9%)
Yes
(VL=1.5%)
Correct(0%)
Incorrect
(VL=5%)
Improved
system
(0%)
12.9
Late
(VL=3.5%)
Combined-
Harvester
(GL=1.2%
VL =
Yard(VL=4%)
10.2
6.2
11.2
26
27
28
Correct(0%)
Incorrect
(VL=5%)
No
(0%)
1.5%)
to invest the dryers and harvesters and run
these equipments. Thus, benefit from advanced
technology will be brought to the farmers via
cooperative. The estimation of physical and
financial benefits in our project showed that in
the components of benefits from drying,
benefits from drying losses was highest. But
the farmers didn’t gain this benefit because
they didn’t possess white rice as analysed
previously. This explains why at this stage the
number of dryers increased slowly. For
example, in 2006, the number of dryers in
MRD was 6200 units. Most of these dryers
were installed in the farmers place. In 2009,
this number was only 6600 units, i.e., there
was only 400 units installed in three years. For
further rapid improvement, either the dryer
should be installed in the milling plants or our
proposed model (Figure 4) should be
considered. In this project we have
experimented integration of harvesting and
drying. However, one additional step is
required to complete the post-harvest process,
e.g., the milling step. This step is very
important as it produces the final product
(white rice) in the chain of post-production of
rice. The benefit will be higher if farmers can
manage also the milling operation to produce
white rice. This model will work if a group of
cooperatives unitedly invest and run a milling
plant.
The total losses is the accumulation of losses
of every step, namely harvesting time,
harvesting method, threshing, drying (sun
drying or mechanical drying), and milling. For
example, the highest losses goes to line 8, at
20.6% total losses, which practices late
harvesting (3.5%), manual cutting (2.9%),
threshing (1.5%), field drying (8.7%), and
normal milling system (4%). In contrast, in
case the new technologies are applied to the
whole process, total losses can be reduced to
2.7% as demonstrated by line 6 (using correct
harvesting, combine-harvester, no threshing,
correct drying technique and advanced milling
system). The total losses can be reduced
significantly if any intervention opportunity is
introduced to any step. For instance, sun
drying in line 8 is replaced by correct
mechanical drying can reduce the total losses
to 11.9% (line 10). When smallholder farmers
and cooperatives want to upgrade rice
production technology, Table 9 can be used as
a reference tool to estimate the percentage of
losses that can be prevented.
3.8 Rice management model
Figure
4
describes the integrated rice
management model developed by this project.
We propose a cooperative model where the
farmers share the money via cooperatives to
run their rice post-harvest chain. In this
system, the cooperative will be strong enough
145
Collaboration for Agriculture and Rural Development (CARD) Program
Capital
FARMERS
RICE
Harvesters
-Dryers
COOP
COOP
COOP
…… ……
Market
COOP - UNION
Milling plant
Storage
Benefit
(Low)
Market
Rice line
Management
Capital line
Benefit
(high)
Figure 4. Proposed flow chart for integrated rice management model based on the group of cooperatives
that will handle the rice from harvesting to milling
rice
post-harvest
processing
by
the
3.9 Capacity building
publications of scientific papers.
Within three years of project implementation
period (2006-2009), the project work and
research, extension, training activities have
mobilized a large number of NLU staff
members. It was shown that the engagement of
stakeholders including NLU staff members,
extension workers and pilot cooperatives in the
project helped to contribute to the capacity
building of those stakeholders. NLU staff
members have been engaged in collecting
baseline information, undertaking research
experiments from field to the laboratory,
implementing data analysis and writing both
project reports and scientific papers and
training of the farmers and service providers.
Thanks to the establishment of a laboratory for
CARD project, the capacity of NLU in rice
research and rice testing ability has been
strengthened. Thus, the rice processing and
analysis have been someway part of the
teaching activities in NLU. Consequently, the
outcome was not only useful for stakeholders
The extension activities of this project also
mobilized many local extension workers from
various districts. In addition to training
workshop, extension workers also took part in
other project activities on-site such as
collecting baseline information, conducting
experiments. These project activities were very
good opportunities for extension workers
gaining further knowledge and expertise in rice
post-harvest technology. This training enabled
extension workers to apply gained knowledge
on rice for the consulting or rice technology
transfer to smallholder farmers and organise
their own training activities for untrained
extension workers and farmers. Milling
workshop and experiments were also organised
to provide information on advanced milling
technology to service providers. This project
also provided smallholder farmers better
knowledge on pre- and post harvest technology
of
rice
through
training
sessions,
demonstrations and supported equipments for
pilot cooperatives to apply improved
harvesting, drying and milling techniques. The
but
also
contributed
an
improved
understanding to the scientific communities on
146
CARD 026/05 VIE – Control rice cracking kernel
changes in KAS (Knowledge, Attitudes, Skills)
of cooperatives and smallholder farmers were
observed, i.e. less sun drying, more mechanical
harvesting, correct harvesting time, and more
mechanical drying with correct drying
technique.
respondents not being able to apply
mechanical drying. About 63.3% respondents
stated that CARD project and local extension
centres were the providers of these drying
knowledge and information. In addition, the
harvesters
and
dryers
supported
to
cooperatives by CARD project are being
utilised by the members of farmer’s
cooperative whom are small and medium
holder farmers. Number of harvesters and
dryers installed by the farmers are also
increased as a result of training programs in
this project that will benefit all the farmers
including small holders.
3.10 The impact of the project to
smallholder farmers
Awareness of using appropriate farming
practices
of
smallholder
farmers
increased.
Project activities carried out during last two
years have certainly provided benefits to small
holders directly. Extension services through
training sessions, demonstrations, and study
tours influenced the awareness of using
appropriate harvesting and drying practices by
smallholder farmers along with other
participants. This can be confirmed by the
result of farmer survey. For instance, among
162 respondents, 95.1% were aware of the
negative impact of delayed harvesting
compared to the awareness of recommended
harvesting time for each rice variety. Training
activities jointly organised by CARD project
and extension centre provided this knowledge
for 49.35% respondents in addition to the
initiation of smallholder farmers through their
self-learning. There also were 80% of
respondents who knew paddy threshing should
be done immediately after harvesting. There
The benefits gained by Tan Phat A
cooperative from the project.
The benefits gained by Tan Phat A cooperative
from the improvement of harvesting and
drying practices is summarized in Table 10.
The time from 2006 to 2008 is considered as
the developing time where the cooperative
received the knowledge and experiences from
CARD project to improve their own practices
on harvest and drying methods to increase the
grain quantity and quality. From this time
onward, i.e., commencing from 2009, the
cooperative will gain a benefit every year as
shown in Table 10 without further installation
of the equipments. The current investment can
cover 75% cutting by combine-harvesters (18
harvesters) and 23% mechanical drying (6
dryers) of their rice fields using their own
equipments within only 5 days harvesting time
per crop. For the operation time of 22-23 days
per crop, 18 harvesters can harvest triple of
cooperative rice field (3*478ha/crop) and 6
dryers can dry all of cooperative rice field of
478ha/crop.
was
a
decrease in the percentage of
respondents who used sun drying (from 79.5%
in 2006 to 39.75% in 2009) and the number of
respondents using dryers increased by 40%
(8.70% to 47.83% during three years 2006-
2009). The unavailability of dryers and the
high cost of mechanical drying as compared to
sun drying were two reasons that caused 12%
Table 10. Estimated benefits per year from improvement of harvesting and drying technologies of Tan Phat
A cooperative since 2009
Item
Benefits
VND (x million)
USD
Equivalent
machine†
Harvesting
RHLMT
RHCMT
RHSMT
669.5
702.7
1260
2630.2
200
37194
39036
70000
146230
11114
1870
3.7 harvesters
4 harvesters
7 harvesters
14.7 harvesters
3 Dryers
Total
Drying
RDLMT
RDCMT
RDSMT
28.6
0.5 Dryers
1.5 Dryers
5 Dryers
99.7
5500
Total
328.3
18484
147
Collaboration for Agriculture and Rural Development (CARD) Program
period of this project have sufficiently
†The values in column “Equivalent machine”
were the number of harvesters or dryers can be
purchased using the saving money.
informed the community leaders and members
across Mekong River Delta directly or
indirectly.
In these calculated benefits, the cooperative
got 100% of benefits from the reduction of
processing cost (RHCMT, RDCMT) and service
components (RHSMT, RDSMT). However, the
cooperative didn’t get 100% benefits of the
loss component (RHLMT) because most of
reduction of losses was value losses (quality)
rather than grain losses (quantity). For the
current trading system in the MRD, whoever
possesses the white rice will gain benefits from
reduction of value losses. In fact, the traders
and millers possess the white rice and farmers
possess the dried paddy. Thus, although the
improvements on harvesting and drying
processes are done by farmers, the reduction of
value losses (more head rice recovery) is
benefited by the traders and millers. This
happens because at present there is no clear
difference between good and bad dried paddy
in terms of price. In 2008, the price for a good
dried paddy (correct drying, moisture content
14%wb) was 50 VND/kg higher than the bad
dried paddy (incorrect drying or sun drying,
moisture content of 17%) only. This 50
VND/kg is equivalent to the expense for
drying to get 14% moisture. This is because of
the fact that the service providers control the
price of wet and dried rice in addition to the
service fee.
The quality of this CARD project research
outputs is demonstrated by scientific papers
that were published in international journals
and conferences. To date, two scientific papers
derived from outputs of this project were
published in Drying Technology (volume 27,
issue 3, 486-494pp) and International Journal
of Food Properties (volume 12, issue 1, 176-
183 pp). The abstract 'Influence of harvesting
time around grain maturity on rice cracking
and head rice yield in the Mekong River Delta
of Vietnam' was introduced in the event 'Post
Harvest 2009
–
Rice Exhibition and
Conference’ held in July 2009 in Bangkok,
Thailand. The research project entitled
‘Optimisation of high temperature fluidised
bed drying performance of rice by Response
Surface Method’ and ‘Influence of high
temperature fluidized bed drying on the kernel
cracking of Vietnamese rice varieties’ were
presented in 6th Asia-Pacific Drying
Conference held in October 2009 in Bangkok.
4.
Conclusions and recommendations
This paper summarises the major activities,
achievements, and benefits of the CARD 026-
VIE/05 project during the implementation
period from April 2006 to November 2009.
Basically, main experiments related to
harvesting time, harvesting method, flat-bed
drying, and glass transition approach are
completed and final results and conclusions
were drawn. A few days early harvesting
(before maturity) is better than late harvesting
by 4 to 6 days because late harvesting will
make the grain more sensitive to cracking.
Therefore, any delay or longer harvesting time
can cause more losses, as is often the case of
harvesting by hand. The degree of harvesting
time effect is also dependent on the variety. An
optimal harvesting time for highest HRY of
some main rice varieties has been proposed by
this project (Table 1).
In other words, farmers got no benefits by
improving the grain quality via advanced
technologies. For the farmers to gain the
benefits from reduction of losses due to
advanced
harvest
and
post-harvest
technologies, the farmers should possess the
white rice. A model so-called “integrated rice
management chain model” from harvesting to
milling for a better rice quality and higher
farmer income (Figure 3) may help the farmers
to possess the white rice, .i.e., gain the benefits
from reduction of losses.
3.11 Publicity
Some baseline information and activities of
this CARD project have been broadcasted in
newspapers (Khoa hoc Pho thong 08/05/2008;
The fluidised bed drying experiment was
validated the optimisation method of multi-
Vietnam
News-The
National
English
Language Daily on 29/04/2008; Rural
Economic Times May 2008) and local
broadcasting (Can Tho televition in June 2007;
Kien Giang television in December 2008 and
2009). In addition, the numerous training
sessions organised during the implementation
pass
drying
mode.
Changes
of
physicochemical characteristics and sensory
properties of fluidized bed dried rice were also
investigated. It was likely that fluidized bed
drying is a promising rapid drying technique
which can be combined with tempering and
148
CARD 026/05 VIE – Control rice cracking kernel
tower drying or ventilation for multi-pass
drying to increase drying capacity and secure
long term storage of paddy during wet season,
especially, high moisture paddy.
service providers, millers, extension workers
and farmers’ representatives aware of using
appropriate milling technology. These
extension activities had a very satisfactory
impact on the knowledge and farming
practices of smallholder farmers belonging to
the cooperatives involved in this project as
shown in the result of farmer survey.
Two milling experiments using medium (1 ton/
hour) and large (7 ton/hour) milling capacities
were undertaken in Can Tho and Kien Giang,
respectively. The current milling performance
was assessed and a new approach for better
milling performance was discussed. Size of
mill is an important factor that determines the
losses. The small mills which are used by
small farmers showed a low head rice
recovery. Medium and large scale plants had a
high recovery, but still it was far from ideal.
The maximum head rice recovery in large
plants is still around 55%, a well below the
ideal level (60%). This means that the milling
is another important factor to improve the head
rice yield. Dehusking using rubber roll will
improve HRY only when the paddy is dried
correctly up to moisture content of 14-15%.
To build up staff competence in rice
processing technology and quality evaluation,
three NLU staff members undertook the
technical training at the University of
Queensland.
One
Vietnamese
student
completed MPhil degree at UQ (scholarships
supported by AusAID). Vietnamese project
leader and UQ-based project coordinators
visited leading rice research institutes in
Thailand and Philippines. The extension
activities of this project also mobilized many
local extension workers from various districts.
This greatly assisted in the capacity building of
the people involved in the project. In addition,
a rice testing laboratory equipped with analytic
instruments purchased from CARD fund and
refurbishment cost from NLU was established.
This rice analysis laboratory was not only used
for testing of thousands of rice samples from
CARD-based research but also served as
research site of many studies in relation to rice
quality and food texture by a number of NLU
staff members and senior students.
An integrated data on harvest and post-harvest
losses of rice was generated from this project
is helpful to estimate the percentage of losses
that can be prevented if the intervention
opportunity is introduced to the chain of rice
production. We also propose an integrated rice
management chain model from harvesting to
milling for a better rice quality and higher
farmer income. This model can also be
developed through a cooperative-union where
a group of cooperatives invest and run a
milling plant and have control over entire rice
post-harvest chain.
Some selective results of main experiments
were published in recognized international
journals and international conferences. Two
articles were available in Drying Technology
and International Journal of Food Properties.
The abstract 'Influence of harvesting time
around grain maturity on rice cracking and
head rice yield in the Mekong River Delta of
Vietnam' was introduced in the booklet of 'Post
Second main task undertaken in this project
was training activities to disseminate the
information on harvesting and drying practices
to stakeholders. The systematically data
collection and experimental results were
prepared in the forms of training manuals and
leaflets and distributed to stakeholders,
particularly smallholder farmers via training
workshops and study tours. During last two
years, there were total of 2392 farmers and 306
extension workers participated in the training
program. Extension activities including 17
one-day training sessions, demonstrations and
study tours for farmers and local extension
workers were held in 11 districts within Can
Tho City and Kien Giang province in order to
disseminate the knowledge to stakeholders
about the rice cracking, drying and harvesting
practices. A rice milling workshop was also
successfully organised in Tan Hiep district,
Kien Giang province to make local authorities,
Harvest 2009
–
Rice Exhibition and
Conference’ event held in July 2009 in
Bangkok, Thailand. Two research projects in
association with optimisation of high
temperature fluidised bed drying performance
were presented at 6th Asia-Pacific Drying
Conference held in October 2009 at Bangkok.
The estimation of physical and financial
benefits of this project showed that Tan Phat A
cooperative will gain USD 50,326 every year
from the improvement of cost and losses of
harvesting and drying practices without further
installation of the equipments. If the benefits
from service of harvesting and drying are
included, the cooperative will gain USD
125,826 every year. Under the circumstances if
149
Vinh Truong, Tuyen T. Truong, Bhesh Bhandari & Shu Fukai
the advanced system is applied to MRD in rice
production, i.e. correct harvesting, combined-
harvesting cutting, mechanical drying, milling
using modified dehusker, MRD may reduce
13% total losses which are equivalent to USD
190 million per annum.
western rice. Cereal Chemistry, 40, 323-
326.
7
Ntanos, D., Philippou, N., & Hadjisavva-
Zinoviadi, S., 1996. Effect of rice harvest
on milling yield and grain breakage.
CIHEAM-Options
15(1), 23-28.
Mediterraneennes,
8
9
Soponronnarit, S. and Prachayawarakorn,
S. Optimum strategy for fluidized-bed
paddy drying. Drying Technology 1994,
12, 1667-1686.
References
4
Bal, S.,
&
Oiha, T. P., 1975.
Determination of biological maturity and
effect of harvesting and drying conditions
on milling quality of paddy. Journal
Agricultural Engineering Resource, 20,
353-361.
Soponronnarit, S., Wetchacama, S.,
Swasdisevi, T. and Poomsa-ad, N.
Managing moist paddy by drying,
tempering and ambient air ventilation.
Drying Technology, 1999, 17, 335-344.
5
6
Berrio, L. E., & Cuevas-Perez, F. E., 1989.
Cultivar differences in milling yields under
delayed harvesting of rice. Crop Science,
24, 1510-1512.
10 Sutherland, J.W. and Ghaly, T.F. Rapid
fluidised bed drying of paddy rice in the
humid tropics. In Proceedings of the 13rd
ASEAN Seminar on Grain Post-harvest
Technology, 1990.
Kester, E. B., Lukens, H. C., Ferrel, R. E.
M., A., & FIinfrock, D. C., 1963.
Influences of maturity on properties of
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