Development of simple, edible coatings for postharvest life extension and quality maintenance of fruit and vegetables

• Chiang Mai University, Thailand
• University of Newcastle, Australia

Produce coatings based on simple food ingredients include agar (from seaweed), polysaccharides and gums (from plants), gelatin (from animals) and xanthan (from microbes), as well as internationally approved food additives (stabilisers, emulsifiers, thickeners and gelling agents). Produce dipped in the coatings, which are water soluble and easy to apply, is coated with a natural microfilm, which is odourless, tasteless and invisible. The coatings, which can be applied at any stage and later washed off with water, are compatible with the commonly used fungicides.

Further research and development on mechanical (e.g. thickness and strength) and barrier (e.g. permeability to water vapour, oxygen and carbon dioxide) properties of the films, and testing under a range of climates and handling conditions, are essential to optimise the effectiveness and commercial suitability of different coatings on different produce.

Postharvest losses of fresh fruit and vegetables are a major concern, both in developed, and in developing countries. Tropical produce is particularly vulnerable. Even where advanced technologies are available they are not satisfactory, being expensive, complex to operate, and not always effective in preventing chilling injury.

This project aims to develop edible coatings that will extend the postharvest life and maintain the quality of fresh fruit and vegetables handled under ambient or low-temperature conditions in Thailand and Australia. The coatings - which serve to modify atmospheres within the produce - must be simple to apply, non-toxic, accessible and affordable.

Scientists from the commissioned organisation, the Food Industry Development Centre (FIDC) of the University of New South Wales, will collaborate with colleagues at Chiang Mai University (CMU), Thailand, to develop, refine and evaluate a range of coatings for suitability for use on selected fruit and fruit-type vegetables of commercial importance to each country. Thailand will focus research effort on tropical produce, while Australia will concentrate on produce of temperate origin. The development of coating application techniques, especially those suitable for use by small landholders, will be undertaken mainly in Thailand.

The collaborators will undertake limited field evaluation and transport and marketing trials in Thailand and Australia to assess commercial viability using a range of produce treated with newly developed coatings. They will also investigate disease control - a major constraint in the commercial application of coating and film technologies, particularly in the tropics - with the assistance of Dr C Kuek, of the University of Western Australia. The team will interact with other ACIAR project scientists involved in the investigation of tropical fruit disease control; and with the Horticultural Working Group, ASEAN Food Handling Bureau, to enhance technology transfer throughout the region.