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Green-seeds.com:
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POSTHARVEST RESEARCH ON TROPICAL AND SUBTROPICAL FRUITS IN SOUTH
CHINA
Donglin Zhang, Peter C. Quantick
Food Research Centre
University of Lincolnshire and Humberside, 61 Bargate, Grimsby, DN34
5AA UK
Yuebiao Li, Chunyan Guo
Department of Plant Physiology and Biochemistry
South China Institute of Botany, Academia Sinica, Guangzhou 510650
P.R.China
Key words: Postharvest research, Tropical and subtropical fruits,
South China. |
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ABSTRACT
 South
China is located in tropical and subtropical region in the North Hemisphere.
Its ecological conditions make possible the production of tropical
and subtropical fruit crops. Fruit industry is one of main industries
in South China. During the past 20 years, there has been a great development
in cultivation and production encouraged and organised by government.
Gradually, South China has become an area of potential growth for
the production of tropical and subtropical fruits to satisfy not only
the large home population but also export markets. However, postharvest
research and applications are behind production growth in this region
and many tropical and subtropical fruits have not been studied and
handled adequately. Reduction of harvest losses is very desirable.
Post-harvest
research on tropical and subtropical fruits in South China has been
active in meeting production growth and demand of export and domestic
marketing since 1970s. It covers a wide range of tropical and subtropical
fruits such as litchi, longan, bananas, mangoes, citrus, pineapple,
coconut, and betelnut, etc. and the areas of biochemistry, physiology,
and pathology. However, little is known about the post-harvest research
activities in this region outside China since most of research results
and papers were published in journals in Chinese (in China). This
paper reviews: (1) past and current post-harvest research in this
regions; (2) applications of some technology for export and domestic
markets and collaborating research with international affiliations;
(3) the strengths, weaknesses, opportunities, and threats in post-harvest
research in this region.
1. INTRODUCTION
South China is
located in tropical and subtropical region - 105-120E longitude, 18-28N
latitude, and from 20 to 1800 m elevation - in the North Hemisphere.
It is composed of four provinces - Guangdong, Guangxi, Fujian, and
Hainan. The temperature ranges from 38C to -1C with high humidity
and rich rainfall (from 1,500 to 2,000 mm). Its ecological conditions
make possible production of tropical and subtropical fruit crops.
The origin of many fruits such as Litchi (Lychee), Longan, and some
cultivars of citrus (Ponkan and Tankan) is believed to be in South
China, where they have been grown for as long as 30 centuries. Also
many other tropical and subtropical fruits such as sweet orange, coconut,
banana, mango, betelnut, and rambutan are grown in this regions. 
Production
statistics for tropical and subtropical fruits in South China have
not been very good, assessments being approximate. The production
of major tropical and subtropical fruits and their changes in South
China are shown in Table 1. South China is the
largest producer of Litchi and Longan with various cultivars and very
good quality. Therefore, the fruit industry is one of main industries
in South China. Since 1970s, the fruit industry has been paid more
and more attention to by the government, industries, and local people.
During the past 20 years, there has been a great development in cultivation
and production encouraged and organised by local governments (Table
1 and 2). Gradually, South China has become
an area of potential growth for the production of tropical and subtropical
fruits to satisfy not only the large home populations that generally
still consume much less fruit than populations in Europe and North
America but also export markets. However, as tropical and subtropical
fruits are very perishable due to their characteristic shapes, structure,
high water content, appearance, physiological characteristics, and
growing conditions, the harvested losses have been estimated to be
up to 40%. Research and application of technology for storage, transport,
and packaging of fruits after harvest are behind production growth
in this region and many tropical and subtropical fruits have not been
studied and handled adequately. Reduction of these losses is very
desirable.
Post-harvest
research on tropical and subtropical fruits in South China has been
active to meet the production growth and demand of export and domestic
marketing since 1970s. It covers a wide range of tropical and subtropical
fruits such as litchi, longan, bananas, mangoes, citrus, pineapple,
coconut, and betelnut, etc. and the areas of biochemistry, physiology,
and pathology. However, little is known about the post-harvest research
activities in this region outside China since most of the research
results and papers were published in journals in Chinese (in China).
This paper reviews: (1) past and current post-harvest research in
this region - physiology, biochemistry, pathology, technology development,
source of funding; (2) applications of some technology for export
and domestic markets and collaborating research with international
affiliations; (3) the strengths, weaknesses, opportunities, and threats
in post-harvest research in this regions.
2. PAST AND CURRENT POSTHARVEST RESEARCH IN SOUTH CHINA
Postharvest
physiology came of age in 1950s when it was chosen as a topic for
review in the first volume of the Annual Reviews of Plant Physiology(Biale,
1950), and featured on a cover-page article in Scientific American(Biale,
1954).
1960s.
Although postharvest research in South China with particular purposes
appeared in 1970s, a pioneering work in 1963, by Li and Yen, attributed
polyphenol oxidase in Litchi peel and suggested that it might be well
related to browning of Litchi fruit (Li and Yen, 1963).
1970s.
Two research projects in the early 1970s became key factors inspiring
postharvest research in South China. The first was a study on prevention
of browning in Litchi peel during deep-frozen storage. Litchi (Litchi
chinensis Sonn.) fruit is a tropical fruit with high commercial
value in the international fruit market. However, within 2 or 3 days
after harvest its pericarp becomes desiccated and turns brown; it
decays and its flavour is lost. This project was organised, sponsored,
and carried out by South China Institute of Botany, South China Agricultural
University, and Guangdong Cereals and Oils Import & Export Trading
Company to seek a proper technology to prevent browning in frozen
Litchi exported to Japan. A successful technology had been produced
to prevent browning of frozen Litchi fruit using sulphur compounds
and food additives. The modified technology is still used by the industry
for export. With this successful work, one pioneering paper entitled
"Study on Prevention of Browning in peel of Litchi during deep-frozen
storage" (Guangdong Postharvest Research Group, 1975) was produced.
The
second was a study on prevention of postharvest granulation and decay
of citrus. As we know, posthavest granulation is a kind of common
physiological disorders, occurring late in storage of citrus and causing
serious loss. In 1970s, a considerable amount of Tankan and Ponkan
was exported to Southeast Asia as they were popular for quality and
flavours. However, granulation of Tankan and Ponkan caused considerable
economic losses to export industries. This project was organised and
sponsored by the related exporting industries in Shantou and Guangzhou
Branch of the Chinese Academy of Science and Technology . It was carried
out by the postharvest group of South China Institute of Botany. The
project produced a simple and practical technology for storage of
citrus with very low cost which was to use gibberellic acid or other
plant regulators in combination with using fungicides, picking up
fruits at the appropriate maturity stage, and using proper packaging.
The application significantly reduced granulation and maintained the
quality of the fruits.
During the 1960s
and 1970s, two main groups for postharvest research - the postharvest
group in South China Institute of Botany and horticulture department
in South China Agricultural University - had been established gradually.
There were about 15 - 20 researchers involved in postharvest research
activities (Table 3).
1980s.
Due to the great decision by Deng Xiaoping to open China to the world,
China started its economic reform program by adopting a household-based
farming system in rural areas. The move has led to impressive growth
in agricultural production. Since then, growing areas and production
of fruits in South China have shown a great development under the
encouragement and organisation by local governments (Table
1 and 2). Related to this, postharvest technology
became more and more important to harvested fruits. However, the available
postharvest technologies was very limited and research to produce
useful technologies was significantly behind the development of production.
Early
in this decade, a few main national projects launched and sponsored
by the Chinese Academy of Science and Technology, the Chinese Science
and Technology Committee, and the Commercial and Trading Department
started a new and the most active era of postharvest research in South
China. These projects were involved in storage and transport technology
of Litchi, Citrus, Mango, Pineapple, and Bananas and their postharvest
physiology. Postharvest research in this region became active and
organised research activities with specific purposes. Since then,
the following achievements were obtained.
For
Litchi fruit, research mostly covered storage and transport
technology and physiology and biochemistry. Litchi fruit can be stored
at deep frozen temperatures for a year, non-frozen temperatures for
30 days, and ambient temperatures for 7 - 10 days; a series of comprehensive
technologies including harvest maturity stage, packaging, temperature,
humidity, and preservative treatments were obtained from these research.
South China Institute of Botany and South China Agricultural University
played key roles in these activities. More than 20 papers on postharvest
physiology and technology of Litchi fruit had been published. Among
them, a few influential papers need mentioning here. The first, by
Tan and Li (1984), was about partial purification and properties of
polyphenol oxidase from pericarp of Litchi. It was believed to be
the first paper giving a better understanding about the properties
of polyphenol oxidase in Litchi peel and creating some methods for
research on browning of Litchi which are still adopted today. Subsequent
studies (Tan and Zhou, 1987; Lin et.al.,1988a and 1988b) enriched
the knowledge about polyphenol oxidase in Litchi and its relation
to browning. The second, by Chen et. al.(1986), demonstrated that
the production of ethylene in Litchi fruit changed during storage.
In addition, Li et.al. (1986) made a good exploration on respiration
of various Litchi fruits. Chen et.al. (1988) and Li et.al. (1983)
explored the suitable temperatures for storage of Litchi.
For
Citrus fruit, research has mainly covered storage of Ponkan
and Tankan that are main cultivars in South China. Ponkan can be stored
at ambient temperature for 90 - 100 days and Tankan for 150 days without
serious granulation, flavour loss, and decay. A few papers were published
about this subject (Liu et.al 1988; Chen et.al. 1985; Chen et.al 1983;
Chen et.al 1982; Tan et.al. 1985). These studies intensively explored
and made considerable progress on the granulation of citrus and its
control. Some practical technologies for control of granulation and
decay were produced and spread to industries and farms.
Decay
of citrus during storage and transport became a serious problem with
the growth of production. Fungicides became a main tool to control
decay. However, overuse can cause resistance of moulds to fungicides.
Work of Yang et.al.(1986) warned that resistance of Penicillium
digitatum sacc to benzimidazole appeared due to overuse and gave
some suggestions to deal with this problem.
Replacing
chemical fungicides (causing risk to human health) with natural antifungal
materials and essential oils has become a popular topic in the world.
Chen et.al.(1986) and Chen et.al.(1990) demonstrated that there were
positive effects of natural antifungal essential oils - 821A and 821C
on citrus storage. In those research and applications, harvest citrus
fruit was individually wrapped with packaging materials added with
natural antifungal essential oils - 821A and 821C. Inside packaging,
the essential oils were released continuously to control growth of
Penicillium. This technology has been spread to producing areas
of citrus in South China, even Southeast Asia and Taiwan.
For
Mango, Anthracnose (Colletotrichum) is a main disease
causing decay and commercial devaluation of harvested mangoes. Liu
(1984) suggested that pathogenic fungi such as anthracnose on mango
fruit are latent and a main cause of serious decay. Huang and Yang
(1988) demonstrated that a 53C hot treatment in combination with fungicide
can reduce the decay. Mango fruit can be stored at ambient temperatures
up to 15 days and at low temperature for about 30 days.
Pineapple
Blackheart (a physiological disorder) and decay are main problems
in the storage of pineapple with losses was up to 40%. Work of Tan
et.al (1989) demonstrated that exogenous gibberellic acid treatment
could induce blackheart of pineapple fruit. Subsequent studies on
storage of pineapple were made.
Bananas
During this decade, a considerable amount of banana was transported
from South China to North China. However, improper handling, decay,
and poor conditions for transport caused losses up to 40%. Research
was mainly focused on improving storage and transport technology.
Banana fruit can be stored at low temperature for 40-50 days and can
be transported to most areas in China. Some results on physiology
and technology of harvest banana were published (Li et.al 1988; Huang
et.al 1988; Zhang et.al. 1990).
Longan
In this decade, research on the storage of Longan was very weak although
the growing areas increased dramatically. Some papers need mentioning.
The first, by Ye and Wei (1981), demonstrated effects of controlled
atmosphere on storage of Longan. The others, by Chen and Hong (1982)
and by Cai (1988), showed some preliminary work on the decay control
during storage of Longan.
During
this decade, there were about 90 - 100 scientists and graduates involved
in postharvest research activities in South China and distributed
in South China Institute of Botany, South China Agricultural University,
Guangxi Agricultural University, Fujian Subtropical Botany Institute,
and Hainan Tropical Crop Institute.(Table 3).
Due to the opening policy, some scientists had opportunities visiting
developed countries for advanced technology and management, which
promoted mutual or multilateral academic exchange and collaboration.
1990s.
Early in this decade, in spite of reduction of financial support from
the central government, research activities are still active because
of support from local government and industries.
Jiang
and Chen (1993) indicated that changes in polyamine in peel of Litchi
is related to browning and exogenous polyamine treatment could alleviate
browning. Liu et.al. (1991) made a further study on the relationship
between the browning and polyphenol oxidase, peroxidase, and their
compartmentation in Litchi pericarp. Lin et.al. (1994) demonstrated
that organic radicals and colour of Litchi pericarp could be affected
by growth regulators, antioxidants, and oxidants and browning is at
least partially related to the increase of organic free radicals.
Zhou
et.al. (1993) and Tang et.al. (1995) reported the effect of exogenous
gibberellic acid and chilling temperature on the cause and development
of blackheart in pineapple and demonstrated that blackheart was mainly
due to the catalysed oxidation of phenolic compounds by PPO and that
low temperature or gibberellic acid markedly increased PPO activity
and catechol, chlorogenic acid, and caffeic acid to accelerate the
blackheart.
Jiang
et.al. (1995) demonstrated that the activation of latent pathogenic
fungi in mango was related to the development of fruit ripening and
chitinase and -1,3-glucanase increased gradually during fruit ripening
and pathogenesis. Ji et.al. (1994) also made some studies on storage
of mango at low temperature and its chilling injury.
In
this decade, biological control become a popular topic (Zhang, 1992).
Jiang et.al. (1993) conducted a preliminary study on control of decay
in citrus by green mould with Bacillus subtilis.
A
further study on mechanism of granulation in citrus was done, indicating
that changes in ABA and ethylene is related to granulation of citrus
(Jiang et.al., 1992a).
Pan
(1994) demonstrated that harvested Longan fruit has active physiological
characteristics and particular structure on skin surface when fully
mature.
Browning
in coconut and betelnut was also studied. A work of Jiang et.al. (1992b)
demonstrated that the principal browning substrates of betelnut were
chlorogenic acid and dopamine and browning was related to poloyphenol
oxidase. Research on coconut indicated that browning is related to
polyphenol oxidase and changes in specific substrates (Jiang et.al.
1992c and Jiang, et.al.,1992d).
Reduction
of support from the central government has led to seeking mutual or
multilateral collaboration work with industries and extension of available
technologies to industries. The number of researchers declined to
60 - 70 during this period.
3. APPLICATIONS FOR DOMESTIC AND EXPORT MARKETS AND INTERNATIONAL
COLLABORATIONS
As
we know, the ultimate purpose of research is that the produced technologies
are extended for industries to use. Therefore, local government and
institutions not only support and encourage extension of technologies
but also make effort to organise collaborations between institutions
and industries.
The
successful technology for deep-frozen Litchi has been used by the
industry for export of up to 100 tons of Litchi to Japan since 1970s.
The
technology for control of granulation and decay of citrus has been
spread to industries and farms. It became a common technology for
storage of citrus in South China. A considerable amount of citrus
is transported from South China to Northeast China and Northwest China.
With
improvements in storage and facilities for transport, transporting
Litchi fruits to distant markets become possible. In 1985-1986, South
China Institute of Botany, Guangdong Fruits & Vegetables Co.,
and Guangzhou Suburban Fruits & Vegetables Co. made a semi-commercial
trial to successfully transport up to 80 tons of Litchi fruit to Beijing,
Shanghai, and Nanjing.
In
1985, South China Institute of Botany collaborated with CSIRO in Australia
and made a successful trial to transport a small amount of treated
Litchi fruit from Guangzhou to Sydney. This project produced a paper
by Huang and Scott (1985) published in Tropical Agriculture. It was
probably the first paper published in international journals by postharvest
scientists in South China.
By
the end of 1980s, South China Agricultural University and Dongguan
Fruits Co. successfully transported about 20 tons of Litchi to Canada.
In
1991, South China Institute of Botany and Guangzhou Fruits & Vegetables
Co. made a successful commercial business to transport up to 200 tons
of Litchi to Beijing, Tanjing, Northeast China, Inner Mongolia by
train and up to 20 tons to Singapore by sea.
In
1994, a small amount of Litchi was sent by South China Institute of
Botany and University of Lincolnshire & Humberside to UK to explore
the possibility of Chinese source of Litchi for UK market. Subsequent
research on applications of coatings on control of browning and decay
during storage of Litchi have been made (Zhang et.al. 1997; Zhang
and Quantick, 1997).
At
the end of 1980s, South China Institute of Botany successfully transported
about 20 tons of mangoes to Beijing.
Early
in 1990s, South China Institute of Botany and a private company successfully
developed a technology to control browning and decay of sculptured
young coconuts and increased its commercial value as 10 times as unprocessed
ones.
In
1994, a project on postharvest physiology of Litchi and other subtropical
fruits between South China Institute of Botany and Agricultural Research
Organisation of Israel was launched. Since 1994, a collaborating project
on developing natural edible coatings for fresh fruit vegetables has
been sponsored by Australian Centre of International Agriculture Research
(ACIAR). In addition, there is another progressing project on blackheart
of pineapple between South China Institute of Botany and CSIRO.
4. FUTURE
South
China is rich in tropical and subtropical fruits and becomes a very
good source of tropical and subtropical fruits for huge domestic market
and could be an important source of tropical and subtropical fruits
for international market (Far East, Middle East, and Central Asia).
However, postharvest industry in this region is still to be planned,
organised, and developed on modern scientific lines.
Several
constraints on effective loss reduction of food are as follows: (1)
lack of effective co-ordination of activities between institutions
and industries involved in loss prevention (research, training, extension,
and marketing); (2) lack of trained personnel at all levels in postharvest
technology (research, farm management, warehouse management, quality
control, and extension); (3) lack of information on postharvest technology
that has been found effective elsewhere and on other fruits; (4) lack
of an effective transport and distribution system; (5) lack of quality
standards and differential pricing policies of national governments;
and (6) lack of financial supports for institutions to further and
intensively study particular and valuable fruits and develop new technology.
In
addition, a little is known about the post-harvest research activities
in this region outside China since most of the research results and
papers were published in journals in Chinese (Table
4). Recently, this situation is being changed gradually.
Although
some postharvest physiology aspects related to molecular biology have
recently become important, the extension of available technologies
and research on unsolved and urgent problems are more desirable in
this region. Obviously, to deal with the existing problems and to
improve current situation to meet the growth of production and demand
of marketing are challenging tasks to both institutions and industries.
5. ACKNOWLEDGEMENT
Thanks
to Professor X.J.Tan, F.Chen, S.X.Liu, and Y.M.Jiang from South China
Institute of Botany, Academia Sinica, Guangzhou, P.R.China for providing
some valuable data.
6. REFERENCES
Biale,
J.B. 1950. Postharvest physiology and biochemistry of fruits. Annu.
Rev. Plant Physiol. 1:183-206.
Biale,
J.B. 1954. The ripening of fruit. Scientific Amer. 190:40-44.
Cai,
M.Z. 1988. Study on decay and browning control of stored Longan with
SO2. Acta Fujian Agri. Acad. Sin. 5:85-89.
Chen,
F. 1986. The production of ethylene of Litchi fruit during storage
and its control. Acta Hort. Sin. 13(3):151-156.
Chen,
F. et.al., 1988. Study on suitable temperature of storage of Litchi
fruit. Acta Refrig. Sin. 4:5-11.
Chen,
M.D., et.al., 1982. A preliminary study on physiological changes during
postharvest granulation of citrus fruit. China Fruit Research. 4.
Chen,
M.D., et.al., 1983. Postharvest granulation of citrus fruit and its
control. China Fruit Res. 4.
Chen,
M.D., et.al., 1985. Study on postharvest technology to prevent granulation
of Citrus (Citrus reticulata blanco var. Hongju) fruit. China
Fruit Res. 3:11-13.
Chen,
M.D., et.al., 1986. Brief Communication of effects of natural antifungal
materials-821A and 821C on citrus fruit storage. China Fruits. 3:24-25.
Chen,
M.D., et.al., 1990. Study on effects of citrus antifungal preservative
papers and films on citrus storage. Proc. Inter. Citrus Symp., Guangzhou,
China, November 5-8, p814-815.
Chen,
W.J. and Hong, C.Z. 1982. Study on decay control of Longan during
storage. Fujian Agri. Sci. 3:44-45.
Guangdong
Postharvest Research Group. 1975. Study on prevention of peel browning
of frozen Litchi fruit. Acta Bot.Sin. 17:303-308.
Huang,
B.Y. and Scott, K.J. 1985. Control of rotting and browning of Litchi
fruit after harvest at ambient temperature in China. Trop. Agr. 62(1):2-4.
Huang,
B.Y., et.al., 1988. Study on application of ethylene absorbents to
prolong storage life of banana. J. Trop. Crops. 9(2):69-74.
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