Determination of the Physical and Mechanical Properties of Turmeric (Curcuma longa L.)

Abstract

Turmeric is a medicinal crop widely popular due to its curcumin content. While other countries have established the physical properties of this crop, literatures specific for turmeric found in the Philippines have yet been documented. Freshly harvested turmeric rhizomes were randomly selected and their physical and mechanical properties were measured. Test results showed that the rhizomes have an average moisture content of 84.7 %. The samples have mean dimensions of 77.2 mm (length), 23.0 mm (width) and 19.7 mm (thickness). Computations showed that the rhizomes have a geometric mean diameter, sphericity, aspect ratio, surface area, and volume of 32.4 mm, 0.436, 31.6, 3371.2 mm2 , and 19044.8 mm3 , respectively. The gravimetric properties were also determined, and measurements showed that the fresh rhizomes have true density, bulk density, and porosity of 1.002 g/mL, 0.51 g/mL, and 48.8 %, respectively. Frictional properties against plywood (across the grain), plywood (along the grain) and stainless steel revealed that the rhizomes have a coefficient of friction of 0.41, 0.30 and 0.20 against these materials, respectively. The average angle of repose on a flat level surface is 18.6°. The maximum puncture and shear force that mother rhizomes can withstand were determined to be 0.1761 and 0.1708 kN, respectively. For the finger rhizomes, a maximum puncture force of 0.1029 kN and shear force of 0.0899 kN were recorded. Fresh rhizomes were sliced and dried until the final moisture content reached 8 to 9%, in which they were then pulverized. Optical properties were characterized using the CIE L*a*b* color scale and were converted to H-S-B. Preliminary findings showed that hue values for the three classifications were almost the same and were identified to fall between the orange and yellow hue. The dried rhizomes recorded the lowest saturation and brightness values, however, these values increased after pulverization indicating that only the surface color was affected and the interior of the rhizomes retained its vividness.