The
              Report

No. 81: Preservation of export 
native flowers

The full report

This is a summary of a RIRDC Full report: Uptake Preservation of Cut Flowers & Foliage (Pub. No. 00/66) by Margaret Johnston, Alison Fuss, Helen Murphy, Nely Moncada, Daryl Joyce and Bhesh Ghandari. Copies of the full report ($15) can be purchased from RIRDC on 02 6272 4819 or from our our eshop (www.rirdc.gov.au/eshop). The Final Report report can also be downloaded from our website: www.rirdc.gov.au/reports/index.htm

More reliable and cost-effective methods of preserving native flowers and foliage for export have resulted from a project undertaken for the Rural Industries Research and Development Corporation (RIRDC).

A team led by Dr Margaret Johnston, senior lecturer at the University of Queensland Gatton, reports that while most cut flower/foliage exports from Australia are fresh, there is an expanding multi-million dollar drying and preserving industry.

But little research has been done to optimise plant preservation methods and to select the appropriate chemicals to use. Previously processes have been developed by individuals, usually in an unsystematic trial-and-error manner.

The new report is part of RIRDC’s Wildflowers and Native Plants R&D program, which aims to improve the profitability, productivity and sustainability of the Australian wildflower and native plant industry.

The Study

Three informal workshops were held with industry groups in Perth and Albany in WA and at the University of Queensland Gatton campus.

The workshops established a need to look at key problems facing the native flower preserving industry -- leading researchers to try to scientifically identify appropriate chemicals for preserving native cut flowers and foliages.

Current products and processes used by the industry in Queensland and Western Australia were investigated and problems and difficulties producers faced in those states were identified.

Background information was established on how the anatomy and morphology of plants influenced the uptake of preservative solutions and the way post harvest environmental factors may impac t in specific situations was studied.

This included uptake of specific chemicals by specific plants and how various preservatives, dyes, environmental conditions and packaging during storage impacted in the preserving process.

The workshops showed the Western Australia and Queensland groups were experiencing similar problems and difficulties in preserving flowers and foliages, despite the fact that they were working with quite different plant material.

Sourcing the material differed in each state. In Western Australia, it was mostly obtained from natural bushland, while in Queensland it was predominantly harvested from cultivated stands.

Final product variability was the main concern. While natural variability was identified, the time taken to get harvested material into the preserving solution and the lack of environmental controls during processing were also considered key factors contributing to this variability.

The timing issue was exacerbated in WA due to the large distances between harvest locations and processing facilities often causing delays of up to three days.

Poor postharvest handling during that time compounded the problem.

In both states, glycerol was the key preservative. It was used in solution either alone or in combination with other humectants, such as PEG. A range of anti-microbial chemicals and dyes were also added to the uptake solutions.

Western Australia reported problems of leaf drop and mould growth on the preserved plants. It is likely that the long time between harvesting and preserving may have contributed to the leaf drop problem. It is probable that the ‘bleeding’ of glycerol from the leaves of the preserved material encourages the mould growth.

Processors in Queensland were trying to overcome mould development by dipping their product in a fungicide solution. The industry groups in both states were interested in the development of techniques that would control or stop the ‘bleeding’ particularly at high relative humidities experienced in specific markets.

The Results

Overall, there is a general consensus of a lack of specialisation within the preserving industry in Australia. This is compounded by a lack of public research support in the area of optimising protocols and identifying appropriate chemicals for preserving native cut flowers and foliages.

Growers commented that it is difficult to source information on drying, preserving and background information on the principles behind uptake preservation.

The work shows the importance of fresh and healthy plant tissues in the preservation process. It says stems to be preserved should be handled similarly to those sold as fresh flowers. The time between harvest and preservation needs to be minimised to less than 12 hours and stems should be recut before being placed into preserving solutions. Details on how the preservation process can be enhanced by modifying environmental conditions during transportation, handling and processing are given.

The report says there are simple procedures and equipment which can be adopted and used to improve the quality of the preserved stems. The Diagram below shows a relative humidity control system used for storage of stems of glycerined Stenanthemum.

The report recommends special lighting, control of air circulation, humidity and temperature in the processing areas. Glycerol is recommended as the best preservative in most cases and advice is provided on its best use. The report also suggests using red food dyes, added to the preservative solution, for colouring some foliages and makes recommendations on additional research needed to improve the dried flower/foliage products.
 

Figure 1.  The stems in four boxes were used as replicates for determining the initial weight and monthly weight over a 6 month storage period from 9 October 1997 to 9 April 1998. Stems in the fifth box were the source of samples for an equilibrium relative humidity (ERH) test. The change in mass (% initial weight) was calculated each month. Observations were made on colour change, flexibility, sweating or mould development and leaf or flower drop.

 

Summary

The research provides useable methods that the dried and dye sectors of the Floricultural Industry can incorporate simply into their own processing operations to improve their products.

Minor modifications to current practices can add to the efficiencies of the process, to significantly improve the quality of these flowers and foliages.

This should ultimately result in better economic returns for the industry.

The importance of using high quality products that are handled appropriately after harvest is emphasised.

As well, improving the environmental conditions during processing and understanding the different requirement for different species is of great importance.

 Figure 2: Equilibrium relative humidity control System


 

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