Some physical and mechanical properties of fermented Keluwak (Pangium edule Reinw) seed

Fermented seed of the tropical tree Pangium edule Reinw., locally known as Keluwak, have been used as spices in Asian and especially Indonesia cuisine. For further processing and postharvest handling, physical and mechanical properties of the seed are needed. Some physical properties, i.e. length, width, thickness, geometric mean diameter, sphericity, surface area, unit mass and 100-mass of seeds, fraction by weight, true volume, true density, bulk density, porosity, and coefficient of static friction at five different surface (cardboard, stainless steel, iron plate, glass, and plywood) of Keluwak seeds were evaluated at the market moisture content. Also, some mechanical properties, i.e. rupture force, strain, stress and Young modulus at three dimensions axis have been measured. The average length, width, thickness, geometric mean diameter, unit mass and per 100 seeds were 44.94±5.6 mm, 43.35±5.2 mm, 27.40±3.4 mm, 37.36±3.2 mm, 11.47±3.7 g and 1693.39±483.85 g. In the market moisture content, the results indicated 0.87±0.07, 4413.99±733.22 mm², 1.01±0.01 g/cm³, 0.42±0.03 g/cm³, 58.21±3.37% and 69.10±13.84% for average sphericity, surface area, true density, bulk density, porosity and peel ratio of the seed, respectively. Angle of friction for respective cardboard, stainless steel, iron plate, glass, and plywood were 25.52±6.9 deg, 17.40±3.92 deg, 21.40±5.2 deg, 12.27±42 deg, and 24.8±7.45 deg. The average compressive force needed to break the seed at length, width, and thick axis were 295.34±87.95 N, 283.87±83.90 N, and 215.71±65.53 N. The strain, stress, and Young modulus were 0.095±0.03, 2.10±0.71 N/mm², and 23.16±7.20 N/mm² at length axis; 0.069±0.03, 2.66±0.88 N/mm², and 45.44±20.95 N/mm² at width axis; 0.05±0.02, 2.05±0.63 N/mm², and 48.12±22.61 N/mm² at thick axis, respectively.