Karakteristik rheologi gel cincau hitam (Mesona palustris BL)

Abstract

Black grass jelly or often called as black jelly (“cincau” in Indonesian) was produced by boiling parts of black grass jelly plant to get the extract of black jelly. These parts include roots, stems, and leaves. Prior to boiling tapioca is added to the extract in order to set a gel after heating. Every part of black grass jelly plant produces different extract from other parts. The concentration of tapioca is important to get a self – standing black grass jelly. The aim of this research is to investigate the rheological characteristics of black grass jelly produced from every part of black grass jelly plant. The rheological characteristics are measured by viscosity test, uniaxial compression test, puncture test, and relaxation test. Black grass jelly from leaves extract has a higher viscosity than black grass jelly from roots and stems extracts. The engineering stresses obtained from uniaxial compression tests of black grass jelly produced from roots, stems, and leaves extracts were 43.02 (±27.94) kPa, 12.95 (±5.71) kPa, and 389.98 (±168.77) kPa, respectively. Those values were equal to true stresses of 5.43 (±3.51) kPa, 1.33 (±0.59) kPa, and 50.85 (±21.15) kPa, respectively. The stress values from puncture test of black grass jelly (4% b/v tapioca/liter extract) were 0.28 (±0.0084) kPa, 0.29 (±0.0362) kPa, and 4.90 (±0.1393) kPa, respectively. The values for black grass jelly with 10% b/v tapioca/liter extract were 0.73 (±0.0279) kPa, 0.85 (±0.0279) kPa, and 8.86 (±0.2785) kPa, respectively. The results of viscosity test, uniaxial compression test, and puncture test showed that leaves extract produces the firmest black grass jelly. Stems extract are produced the weakest jelly. Both stems and roots extracts produced sticky jelly. Firmer black grass jelly has a good ability to relax after the jelly is compressed instantaneously until certain strain value. This was shown by the relaxation test. The research concludes that black grass jelly from leaves extract has the best rheological characteristics compared to the jelly from other extracts. The rheological characteristics indicate that composites of other extracts (roots and stems) with leaves extract might be potential ingredients for black grass jelly.