One of the most common materials used for packaging is low density polyethylene film. To improve the water vapour transfer of the film, zeolite¡polymer composite films and perforated films are produced. The solid-low density polyethylene composite films were prepared by extrusion of polyethylene beads coated with hot zeolite particles of a definite size range in an industrial extruder (-420/+212, -212/+106, -106/+53 microparticles/g of polyethylene beads). A needle (0.2, 0.5 and 1.75 mm in diameter) attached to the tip of a soldering gun was used for the production of the perforated polyethylene films (1, 3, 6, 12, 18 and 24 holes per 38.5 cm2). The overall evaluation indicates that the water vapour transfer rates can be modified by the composite and the perforated films, which provides packaging material variety for foods of different moisture content. The solid- polyethylene composite films showed less permeability to water vapour than the polyethylene film. This may be attributed to two reasons: the available polyethylene area is reduced by the presence of solid particles and these solid particles have an important sorption property. The water vapour transfer rates increased by the perforated films.

C. Okonkwo et al., 'Assessing food quality in farmer participatory varietal selection of Water Yam (Dioscorea alata L.)', 2004

This publication is a product of an ongoing collaborative research project between the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and the International Food Policy Research Institute (IFPRI). The project aims to introduce dryland crops into the updated IMPACT model and undertake strategic analysis of future opportunities and challenges for SAT agriculture. We would like to extend our sincere thanks to Mark Rosegrant, for providing the necessary background material for the training workshop from which this technical manual has been developed. Special thanks are to Siet Meijer for sharing her experience and offering the training at ICRISAT Patancheru (India), which was very useful in introducing the different variants of the IMPACT model to ICRISAT staff. We also appreciate the coordination and cooperation rendered by our staff to make the training program a success. We thank the Learning System Unit for providing us the necessary logistical support for the training.