Development of a single stage roselle calyx extractor

An 8-litre capacity roselle calyx extractor was developed with Arduino based temperature controls ranging from 30 to 100⁰C. Performance evaluation conducted on the extractor showed that efficiency of the extractor increased as the weight of the calyces decreased at constant mass of water which ranged from 55% to 89%. The effect of extraction time (5, 10 and 15 minutes), process temperature (30, 50, 75 and 100⁰C) and calyx-water mass ratio (1:50, 1:20 and 1:10) on the pH, density and colour of the extract was determined. The pH ranged from 2.4 to 2.9 and density was from 1.02 to 1.05gcm-3. Statistical analysis conducted showed that temperature and calyx-water mass ratio has a linear significant effect (p<0.001) on all the responses while time had a linear significant effect (p<0.001) on all responses except density. Time and temperature had interaction significant effect (p<0.01) on pH, while temperature and calyx-water ratio had interaction significant effect (p<0.01) on the density of the extract. Calyx-water ratio had a quadratic significant effect (p<0.001) on the pH and colour of the extract. The contour plots presented the interactions between the factors and their responses. This study demonstrated that roselle calyces extract can be produced more efficiently than practices currently available and also that processing conditions are very important in the quality of extracts produced.