Assessment and improvement of quality management during postharvest processing and storage of coffee in Papua New Guinea

• PNG Coffee Industry Corporation, Papua New Guinea
• AT Projects, Papua New Guinea

The PNG coffee industry supports 350-400,000 families and earns K300 million pa, but the consistency and reliability of coffee quality has declined with the move to the low-input management of the smallholder industry (>85%, the remaining plantation and 'block' production has received higher prices). Despite this general decline, premium PNG coffee retains a good reputation amongst customers and there is good scope to build demand for PNG coffee by improving marketing and quality.
PNG highlands coffee is of the arabica species, and the genotype x environment (G x E) potential is ideal for good quality coffee. However, critical postharvest steps from harvest, through wet processing, drying, grading, storage and transport, affect coffee quality and grade/sales potential, while further steps (roasting, grinding etc.) affect end-market opportunities for the coffee quality/grade received by the roaster.
Farmers can sell ripe coffee cherries, semi-processed (parchment stage) or dehulled (green) beans to processors or exporters, with higher price/return potential for growers who process to the parchment or green bean stages. Key elements of the quality deterioration that can result from grower processing are: mouldiness and the development of off-flavours due to inadequate drying and storage, and poor grading (product variability, mixed ripe and green cherries, inclusion of small or defective beans or foreign matter). Income to smallholders is 10-25 per cent lower than it could be if product attributes and quality were consistently acceptable.
In the 1990s, the PNG Coffee Industry Corporation (CIC) undertook research and began to implement quality management strategies which began to reverse the quality deterioration experienced in the 1980s. There is continuing interest amongst farmers to address the technical and economic factors that underpin the quality problems in processing (particularly wet processing and drying), storage and marketing, and to improve produce uniformity.
The project complements ASEM/2004/042 on improvement of coffee marketing, because it will provide options for processing, drying and storage that allow growers to reliably supply higher quality coffee where a marketing system is in place to facilitate payment for higher quality characteristics. The strong links with ASEM/2004/042 will lead to joint surveys and information sharing.

Project objectives are to:
assess postharvest system constraints to smallholder management of coffee quality and product consistency;
develop and test solutions to system deficiencies, with particular attention to improvement of drying and storage;
devise and implement strategies for the adoption of system improvements.

The project emphasises farmer-acceptable strategies to optimise coffee quality and consistency through improved wet processing (while minimising water use and waste water pollution), drying (while improving efficiency/optimising fuel demands) and storage (while reducing moisture build-up and mouldiness).
Project methodology requires a mix of socio-economic and technical skills, to undertake a systems assessment and establish baseline information on the social and technical dimensions of quality management from harvest through processing and storage to marketing. Focus will be on representative sites/communities (in Aiyura, Goroka and Marawaka) that are committed to improvement of quality and marketing.
The technical parameters of PNG coffee quality are being assessed, and the findings of the survey data utilised to devise feasible postharvest system improvements that optimise quality management. Finally, potential technical innovations are being developed and tested in partnership with farmers, with successful innovations scaled up and promoted more widely.

The project members undertook a major assessment of postharvest system constraints to smallholder management of coffee quality and product consistency. The implementation of the final socio-economic survey component also provided an avenue for the dissemination of information on postharvest best practice. As a result of the survey, the project teams developed and tested solutions to system deficiencies, with particular attention to improvement of drying and storage.
The team tested an ecoprocessor, which reduced water usage in coffee processing and combined three unit operations into one. Results of controlled trials at the Coffee Research Institute (CRI) have been positive. The testing of the eco-processor is still progressing. A second unit (with a petrol engine) has been imported and is currently being used in demonstration trials at village level. Training is their use is required to ensure selection of the correct unit for the coffee type, and adjustment of the equipment can then give a similar product to conventional processing.
Sun-drying experiments were carried out using the traditional sun-drying system on various surfaces mounted on drying tables. Studies on major factors affecting sun-drying have given surprising results. The major factors considered were drying surface, elevation, shading and stirring. The current method (using blue plastic tarps) gives a result comparable with the optimum method.
Computer simulation studies of solar drying revealed that this was not a suitable design for the culture and climatic conditions. Firstly, the growing climate is cold and wet, secondly a high collection area is required, and thirdly a high degree of maintenance would be required to keep them operational. For these reasons it was decided not to continue with studies on solar dryers.
Drying studies continued throughout the project, and the third possibility for improving drying was a relatively new development, the greenhouse dryer. The dryer differs from solar dryers in its use of heat recycling. Smallholders in coffee growing areas of Colombia have adopted them, and early results indicate that this option can work with a fraction of the space required for a solar dryer. A new design of this type of dryer is currently being tested and will be compared to the traditional sun-drying system.
Work also measured chemical quality, including studies on best drying temperature, chemical changes during storage and chemical ratios during roasting. Coffee storage trials using dried green coffee beans (Coffea Arabica cv. K7, origin northern NSW) and two storage temperatures (15C and 30C) with a reference sample kept in the freezer at -20C were conducted in environmental chambers for 24 months at the University of NSW in Sydney. The results show a positive effect of higher storage temperature on the aroma precursors in the beans.
A major aspect of the project was the construction and provision of a new laboratory at CRI, designed for measuring both physical (such as density) and heat (such as thermal conductivity) properties of coffee beans. This lab was used for the first time in the analysis of the sun-drying trials, then later used for measuring coffee properties.