Some engineering properties of coffee cherry required for color sorting equipment design

Coffee harvesting is one of the factors that can affect the quality and taste of coffee. Harvesting is usually done when the coffee cherries are physiologically ripe, which is marked by a change in the color of the coffee fruit skin to dark red. Changes in the fruit’s skin color will affect the aroma and taste of the coffee produced. Currently, coffee farmers are still making the selection of coffee cherries manually. The coffee fruit sorter is essential in increasing the sorting capacity and improving good coffee quality. The main objective of this activity was to measure and evaluate coffee cherries’ physical, mechanical, and color properties to support efforts in designing and manufacturing a coffee fruit color sorter. The results of measurement on the main physical properties of coffee cherries obtained that water content 70.78±0.63 %, weight 1.83±0.38 g, volume 1.61±0.33 ml, length 17.56±1.33 mm, width 13.86 ±1.17 mm, thickness 12.53±1.00 mm, Particle density 1.00±0.21 g/ml, bulk density 0.59± 0.04 g/ml and porosity 38.42±13.52 %. Measurements of mechanical properties on the surface of stainless steel, aluminum, and plywood for the static angle of repose were 28.78±0.53°, 31.62±1.07°, and 37.62±0.44°, respectively; for the dynamic angle of repose of 14.47±2.78°, 16.00±1.82° and 17.14±1.91° respectively and static friction of 0.63±0.07, 0.75±0.12 and 0.89±0.09, respectively. The result of color measurement using CIE L*a*b* analysis showed that the geometrical coordinates of the coffee fruit were L*=70.314±3.644, a*=7.955±4.4935, and b*=3.526.