PH-Postharvest Technology: Optimization of Coir Dust Compaction using the Response Surface Methodology Approach

The response surface methodology approach was used to establish the optimum compaction conditions for coir dust. The independent variables studied were moisture content (12-28% w.b.), compaction load (8·000-12·000 kg) and binding material (0-6%), in a fractional factorial design following a three-level three-parameter design. Product quality attributes such as vertical expansion in mm, failure load in kg, water-holding capacity as a % and final product density in gcm-3were considered as responses. An analysis of variance (ANOVA) showed that moisture content and binding material significantly affected vertical expansion and water-holding capacity but did not significantly affect compression strength and final product density. Compaction load was found to be an insignificant factor to any of the responses within the load range tested. Second-order polynomial models, generated for vertical expansion and water-holding capacity were found to be adequate, while statistically insignificant models were generated for compression strength and final product density. Through superimposition of the contour plot responses, optimum conditions for compaction of coir dust were established with no supplementary binding material. Assessment of the predicted values obtained and their practical implications suggests an optimum compaction moisture content of 17·5% where predicted values approximated the experimental values.