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by Graeme Thomson, Wendy Morgan, Sonja Winkler, Mandy Chew, Christine Frisina and Janine Jaeger

February 2001

RIRDC Publication No 01/01
RIRDC Project No. DAV-128A

Executive Summary

This project aimed to diversify markets for Asian vegetables through a combination of new and improved field practices and postharvest procedures. There is a real opportunity to increase exports and add value on both domestic and export markets if the correct postharvest handling, processing and packaging protocols are developed for targeted crops and products.

The project investigated production costs for Chinese cabbage, baby Shanghai buk choy, Chinese chives, choy sum, daikon radish, Chinese spinach, garland chrysanthemum, water convolvulus and Japanese pumpkin. A review was undertaken of Sydney and Melbourne market prices. Quality descriptor language manuals were prepared for Chinese cabbage, choy sum, gai lum, buk choy and Shanghai buk choy. Postharvest research focussed on the development of modified atmosphere packaging for whole produce, including Shanghai buk choy, choy sum, gai lum, hot mint and Chinese chives. Protocols were developed for preparing salted Chinese cabbage (varieties Harusakari and Matilda) for the Japanese market. Minimally processed stir-fry mixes, and associated modified atmosphere packaging, were developed using fresh and canned Asian vegetables.

Challenges

The project management committee (Wendy Morgan, IHD; Sam Yiu, Oriental Merchants Pty Ltd; Graeme Thomson, IHD) met on a monthly basis to discuss project objectives and progress. Research components of the project, especially those of a postharvest nature, were undertaken to address field issues and commercial problems encountered by Oriental Merchants in the process of supplying quality vegetables to major supermarket chains.

The fragmented nature of the 'fledgling' Asian vegetable industry presented specific problems to Oriental Merchant. Primary growing areas are diversely located through the Eastern seaboard and while this presents opportunities for vegetable diversity, the logistics of sourcing and transport are made more complex. Asian vegetables are alive, many are leafy and fragile, and therefore require careful handling and transport to ensure that consumers have access to a product in top condition.

Asian vegetable growers often have a non-English speaking background and consequently transfer of technology needs special attention. The infrastructure for optimum postharvest handling of crops is often not currently available for use in communities growing Asian vegetables. The future should see improved vegetable quality as a consequence of correct handling awareness, and investment in equipment (e.g. cooling).

Oriental Merchant now supply 25 Safeway & Franklins stores with around 20 different types of Asian vegetables: Chinese buk choy, baby Chinese buk choy, Shanghai buk choy, Chinese cabbage, Chinese mustard green, choy sum, green choy sum, Chinese celery, Chinese chives, Chinese flowering chives, Chinese lettuce, Chinese spinach, hot mint, kan kong, taro shoot, perilla leaves, penny wort, snowpea shoot, spearmint and watercress. These vegetables are considered ‘leafy’ and are particularly prone to wilting, yellowing etc. after harvest.

Postharvest requirements

Good postharvest management delivers horticultural produce to the end consumer in a condition which is virtually unchanged from harvest time. Handling should avoid mechanical injuries, preserve the product's food reserves and storage life, restrict water loss and avoid proliferation of microorganisms.

To develop new modified atmosphere packaging applications for Asian vegetable crops their rates of respiration needed determination. Storage trials have been completed for Shanghai buk choy, gai lum, choy sum, Chinese chives and hot mint. These vegetables generally stored better at 1^oC than at higher temperatures. However, domestic distribution chains cannot currently guarantee optimal temperatures and with this constraint in mind, 4^oC was used for package development in some instances.

Modified atmosphere packaging was tested for each of the 5 vegetables and trial results have been comprehensively documented. For buk choy, choy sum and gai lum, initial trials focussed on liners for 10kg cartons but later work shifted to 5kg (approx.) to meet new Oriental Merchant supply requirements. Compared to air storage, product held in MA generally had superior appearance at out-turn, was greener and less affected by storage rots. MA carton liners made from polyethylene film were developed in conjunction with a commercial packaging company.

If stored at 0^o to 1^oC in MAP, Shanghai buk choy would have sufficient storage life to survive sea export to SE Asia if initial quality was of a very high standard.

For the herbs, Chinese chives and hot mint, consumers are believed to prefer to purchase small amounts. It is recommended that samples of 50g be stored in MA bags made from 50m m thick ICI BOPP propafilm. At 4^oC, storage life in these bags is expected to be 16 days for the hot-mint and 14 days for Chinese chives.

Fresh-cut stir-fry mixes

Minimal processing is an innovative way of adding value to fruit and vegetables. The perception by consumers of fresh, nutritious, convenient, ready to use products is making these commodities increasingly popular.

There are many different types of fruit and vegetable preparations available in the market place. These include freshly squeezed fruit juices, frozen products, lettuce and mixed vegetable salads, fruit slices and salads, peeled products and ready to cook vegetable mixes. This last group includes stir-fry mixes which generally contain cabbage, carrot, broccoli and cauliflower florets and snow peas. To date none have contained any traditional Asian vegetables.

There is very little information available on the response of Asian vegetables to minimal processing and how they should be packaged and handled. Experiments in this project tested post-processing behaviour and determined packaging requirements for a range of novel Asian stir-fry mixes. One mix was developed which included buk choy, broccoli, carrot, bamboo shoots, baby corn, snow peas, water chestnuts and red cabbage.

Salting of Chinese cabbage

A consistent aim throughout the work undertaken for Project DAV-128A was improvement of postharvest practices to deliver fresh Asian vegetables in optimum condition to consumers. For export markets this can be difficult to achieve because long journeys by sea often necessitate the use of complex packaging and storage requirements for live, fresh product. The value of whole, fresh vegetables often does not justify the use of quicker, but far more expensive, air transit.

The project developed processing procedures for salted Chinese cabbage, a product which is physiologically dead and therefore simpler than fresh produce to store and handle for export. Salted cabbage is produced by 'value-adding' activities and this brings additional benefits to the Australian economy. RIRDC's Research Paper No 95/14 determined that Australia was in a good position to supply the Japanese market with salted vegetables, and salted Chinese cabbage is Japan's second most popular pickled vegetable.

Australia currently produces Chinese cabbage of high quality but the procedures required for processing into salted product were not previously fully elucidated. Salting trials undertaken in this project were in conjunction with a consultant from the Australian pickling industry (GeeVee Pickles Pty Ltd) and have been fully documented. Through GeeVee, an approximate protocol for salting was initially obtained from a Hiroshima food company. However, trials were needed to determine use of appropriate temperature and physical pressure. Quality assessment (including comment on product sent to Japan) considered appearance, taste and texture.

Temperature and pressure treatments during preparation were found to have important effects on both appearance and taste. The cultivar 'Matilda' was preferred because of its yellow coloured heart.

The salting protocol developed in this project puts the Australian food processing industry in a position to capitalise on recognised export opportunities to Asia for minimally-processed, salted product. The salted Chinese cabbage produced by this protocol conforms to Japanese market requirements and trial export shipments were well received. The salted cabbage produced in our trials was assessed at the stage where it could be used immediately, or further processed and fermented to produce a product such as kimchi. Future work could examine the cost effectiveness of various shipping methods, and the procedures required to prepare other products such as salted daikon. Air freight is probably not an economic option.

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Last updated: 16 March 2001
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