Improving postharvest quality of temperate fruits in Vietnam and Australia

ACIAR project PHT/2002/086 'Improving postharvest quality of temperate fruits in Vietnam and Australia', will assist fruit industries by establishing and extending regionally feasible techniques for growing, maintaining and selling high quality temperate fruits such as peaches, plums and nectarines..

The signing presentation for this project took place on the 31 August 2004 and project activities commenced soon after.
Broadly, this project will
establish and extend local best practice fruit production techniques as an adjunct to the earlier introduction of high quality stone fruit varieties &
define and improve fruit handling throughout the Vietnamese supply chain

A planning meeting held at Lao Cai Vietnam (February 2005) involved almost all project staff and developed the strategies which were needed to fulfil the project's objectives.

This project is exploring various means of producing high quality fruit, maintaining quality and reducing postharvest losses and significant progress was made during 2004/05.

Understanding the market. Before innovations introduced through this project can be implemented, the current fruit production system must be understood. Surveys conducted this year highlighted key regional differences in distribution chains, handling and target markets. Economic data was also gathered so that the impact of innovations can be better understood as the project progresses.

Making orchards work better. The production of high quality fruit begins in the orchard. Vietnamese fruit compares poorly with its imported market-place competition. It is small, immature and often damaged or diseased. Many of these problems have their origins in relatively poor orchard management. During the 2005 Vietnamese fruit season (April - July 2005), seven orchards were selected across three fruit-growing districts; Sa Pa and Bac Ha (Lao Cai Province) and Moc Chau (Son La Province). These orchards contained French peach and Tam Hoa plum trees. Experiments have been set up to examine how improved management can produce improved fruit. These orchards will serve as demonstration plots later in the project.

Harvest indices. In the past fruitin northern Vietnam, has been harvested green-hard to avoid fruit fly infestation and better withstand the rigours of harvest, handling and transport. Fruit fly control through bait-sprays is now available and this project will improve handling management. Research has begun to determine a harvest maturity which will deliver fruit to consumers when it is most appealing. A trial was conducted during the 2005 fruit season and examined fruit attributes such as blush, taste and aroma of fruit harvested at various maturities. This will lead to a harvest timing recommendation.

Disease management. Diseases such as brown rot and Botrytis rot cause significant losses to the Vietnamese fruit industries. During the first year of this project a system to control diseases using cultural techniques and locally available fungicides was developed and will be tested over coming seasons. Dipping fruit in the fungicides carbendazim and iprodione after harvest was shown to decrease postharvest disease occurrence by 25 to 50%. Other experiments being conducted in Vietnam and Australia are beginning to investigate the use of non-fungicide options such as biological control and aromatic oils for controlling diseases.

Improving packaging. In order to get sufficient chill to produce fruit the Vietnamese temperate fruit industry is based in the mountainous north-west provinces. The distance between the production regions in this project and their markets varies between 3 (Moc Chau to Hanoi) and 72 hours (Bac ha to Ho Chi Minh City). We have shown that during transport of Tam Hoa plums from Bac ha to Hanoi fruit core temperatures can approach 32C. Fruit is also subject to compression and bruising because of inadequate packaging. Losses of fruit are high.
Impact during transport is damaging fruit. Plans are being developed to trial a number of packaging materials during the 2006 fruit season. These materials will need to be locally available and relatively inexpensive.

Ethylene inhibition, quality maintenance and improved storage life. Aminoethoxyvinylglycine (AVG) is a naturally occurring fermentation product that inhibits ethylene production. Preharvest application of AVG has been shown to have a number of benefits including delaying harvest, improving firmness, increasing soluble solids and extending storage life. The level of benefit derived from AVG application depends on variety, fruit maturity and storage conditions. A trial was conducted in 2005 to determine if application of AVG before harvest could lead to quality benefits postharvest. Specifically, AVG has been shown to improve fruit firmness which would be of benefit in Vietnam given current transport systems. Rain during this trial resulted in fruit being harvested earlier then desired. AVG provided no benefit under these conditions. However, the trial will be repeated next year.

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Fruit quality has improved in experimental orchards across three north Vietnamese peach and plum production regions. This improvement is the result of simple management techniques taught to Vietnamese project staff and passed on to Vietnamese farmers. These techniques cost very little to implement. The addition of fertilisers, mulches, canopy management , fruit thinning and pest management has led to larger, better quality fruit and farmers are now receiving better prices for their produce. Our initial strategy has been to conduct our experiments on commercial orchards, prove our management techniques under Vietnamese conditions and use the results as extension tools. Despite initial scepticism the advocacy of our orchardist collaborators has now become a powerful extension tool which we intend using during the remainder of the project.
Improved prices for farmers will only continue if the rest of the supply chain can consistently supply the Vietnamese domestic market with high quality fruit. Our work has highlighted shortcomings within the Vietnamese fruit supply chain and is now seeking regionally feasible solutions to these problems. In the past fruit has been harvested 'hard green' largely to endure the rigours of transport and withstand fruit fly infestation and disease infection. Maturity indices have been developed which help farmers to decide when to harvest fruit to maximise quality. We now recommend that fruit be harvested when it is much more mature than previously. Consequently fruit is softer and sweeter at harvest. Pest management and packaging are now more important and our work is aiming to facilitate harvest and transport of high quality fruit. A simple technique for dipping fruit in the fungicides carbendazim and iprodione has consistently reduced losses caused by postharvest disease. Additionally the project team is aiming to reduce postharvest disease by using essential oil fumigants and biological control agents.
Because fruit production regions are between 4 and 10 hours from markets transport is a problem. Low commercial returns have not justified expenditure on transport systems. Improved fruit quality will have flow-on effects as wholesalers, retailers and consumers demand delivery of produce in good order. Again, our strategy has been to quantify the problems and then test possible solutions experimentally. Three strategies (fruit conditioning, improved packaging and refrigeration) are being experimentally tested. Fruit conditioning has proven successful in Australia both experimentally and following iits recent commercial introduction. ReTain, a commercial formulation of aminoethoxyvinylglycine (AVG), may be a useful tool enabling growers to harvest their fruit later when it is larger, more highly coloured and sweeter. AVG treated fruit are likely to be firmer enabling them to handle the supply chain better. We are still awaiting results from our second season of experimental work in Vietnam but this approach should be of use. Various types of packaging have been tested to reduce damage caused during transport because of impact and temperature. The most common packaging system in use currently is cardboard boxes which are packed with 30kg of fruit. A number of improvements were trialled during 2006 but unfortunately resulted in no improvement to fruit quality after transport. We will be trying more packaging systems during 2007. The value of refrigeration (at 12C) has been demonstrated experimentally. In the future refrigerated overnight rail transport from Lao Cai City would greatly improve the quality of fruit arriving at Hanoi markets. Despite our experimental proof of feasibility this form of transport remains conditional upon improvements in the quality of Vietnamese peaches and plums justifying expenditure.
Training remains a strong focus of this project. In addition to in-country training, five Vietnamese project scientists have visited Australia for training during 2005-06. Training has included orchard management, integrated pest and disease management, postharvest handling techniques and curation of plant disease collections.
Formal extension of project results will commence during 2007. In preparation for this a number of extension orchards have been established across the Sa Pa, Bac Ha and Moc Chau regions. Individual orchards are small (<1ha) and provide comparisons between traditionally managed trees and those managed using techniques tested experimentally during this project. Improved varieties introduced by an earlier ACIAR project are not widely available to growers at present. The Vietnamese government has recently approved commercial release of a number of these varieties. The coincident release of improved germplasm and training will improve fruit quality. This quality improvement will facilitate improvement along the supply chain as better financial returns justify infrastructure investment.

Production of stone fruit is regarded as an important component of poverty alleviation in Vietnam's mountainous northwest. Despite relatively extensive plantings of plum and peach and historical success, the benefits associated with production have not yet been fully realised and are, in fact, declining. The likely causes of this decline are inappropriate varieties, poor pre harvest management, complex supply chains and inadequate postharvest handling and marketing.
A survey of growers, collectors, wholesalers and retailers was undertaken to gain a better understanding of current supply chain practices and how they impact on fruit quality. These studies reinforced our belief that the supply chain is very complex but notable results included an indication that quality discrimination is carried out at all stages of the supply chain with 69% of collectors indicating that they liked to purchase large fruit. The majority of collectors also store fruit for 1-2 days to obtain a sufficiently large consignment for shipping. These findings justify our emphasis on improving fruit quality and shelf life.
Postharvest disease also limits supply. The diseases brown rot and grey rot (caused by the fungal pathogens Monilinia fructicola and Botrytis cinerea respectively) are the most serious diseases and affected up to 13% of fruit this season in Vietnam. A simple postharvest fungicide dipping protocol has been developed which reduces these diseases. Further improvement can be achieved by applying a preharvest fungicide schedule. The use of essential oils derived from cinnamon and lemon myrtle has proven inhibitory toward these pathogens in in-vitro and simple in-vivo tests. Work is under way to examine the possible use of bacteria and yeasts isolated from peach fruit surfaces as biological control agents.
Fruit maturity indices have now been developed for Tam Hoa plum and Tropic Beauty Peach. It is hoped that this will assist in the timing of fruit harvest to optimise fruit quality and storage. Consumer preference trials undertaken during this year have indicated that our perception of 'correct' maturity may not align with the preferences of Vietnamese consumers who prefer their fruit crunchy, non-juicy and green. The situation may be further complicated because a significant proportion of fruit is bought for religious reasons rather than for eating. A more detailed analysis of consumer preferences was completed during the current Vietnamese fruit season and awaits analysis.
Because fruit production is remote from markets effective transport is critical. Fruit transport in the current industry packaging standard - a 30kg, unpadded cardboard box - results in unacceptable losses. Our trials have shown that a reduction in the size of the package to 10 kg and the inclusion of shredded paper packaging reduces impacts but this does not translate to greater quantities of saleable fruit. This season a number of new packaging options including rice straw, pine boxes and cardboard liners have been trialled. It should also be noted that earlier studies highlighted the fact that losses prior to harvest can be as high as 28% and improvements in pre-packaging handling will become the subject of future work. Refrigeration also offers significant quality and storage improvements. For example, 99% of Tam Hoa plums remain saleable after 21 days storage at 10C and they are firmer than fruit stored at ambient temperatures. This season's trials have examined the feasibility of including refrigerated rail transport as a means of shifting fruit from Bac Ha to the Hanoi markets.
ReTain is a commercial formulation containing the active ingredient aminoethoxyvinylglycine (AVG). During the last two seasons our project has has examined the ability of this product to improve harvest management in Tam Hoa plums and Earligrande peaches. Application of ReTain significantly increased fruit size and extended the harvest period. Manipulation of the harvest period allows farmers to target 'market windows in which they are likely to receive higher prices. In parallel studies in Australia we have been able to demonstrate that ReTain treated fruit can be harvested later, is larger and firmer, and can be stored for longer without storage disorders (e.g. soft tip and flesh bleeding)
A number of key personnel travelled to Australia during this reporting period. Mr Tran Duy Long (FAVRI) visited the Gosford Horticultural Institute to study postharvest management of stone fruit while Mr Vu Duy Hien (PPRI) and Mr Cao Dang Kien (DARD Lao Cai) visited Alstonville Centre for Tropical Horticulture and the Maroochy Research Station to study IPM and crop management.
A large, irrigated planting of low chill peach, plum and nectarine trees was established at Bac ha Research station to aid future extension and research activities.