Sifat Kimia dan Warna Kayu Keruing, Mersawa dan Kapur

Abstract

ABSTRAK Penelitian ini bertujuan untuk mengetahui sifat kimia dan warna kayu keruing (Dipterocarpus humeratus), mersawa (Anisoptera laevis) dan kapur (Dryobalanops keithii) yang sampai saat ini relatif belum banyak diketahui. Sampel pohon diperoleh dari hutan Muara Wahau, Kalimantan Timur. Bagian gubal dan teras diperoleh dari bagian pangkal pohon. Pengujian komponen kimia mengacu pada standar ASTM. Pengukuran warna dilakukan melalui sistem koordinat CIELAB. Hasil pengukuran kadar ekstraktif di 3 spesies pada nilai kadar ekstraktif etanol-toluena (KEET) menunjukkan kisaran pada kayu bagian gubal (KG) 2,37-4,60 % dan teras (KT) 2,58-4,81 %, kelarutan dalam air panas (KAP) sebesar 2,14-6,49 % (KG) dan 1,14-5,77 % (KT), kadar kelarutan dalam air dingin (KAD) adalah 1,61-6,39 % (KG) dan 1,06-3,26 % (KT). Kecenderungan dari gubal ke teras menunjukkan adanya kenaikan nilai KEET, dan penurunan nilai KAP dan KAD. Pengukuran komponen dinding sel pada kadar lignin berkisar 27,39-33,29 % (KG) dan 25,77-34,19 % (KT), kadar holoselulosa berkisar 70,50-73,73 % (KG) dan 65,94-74,84% (KT), sedangkan kadar α-selulosa berkisar 45,83-49,62 % (KG) dan 44,23-52,32 % (KT). Dari gubal ke teras, perbedaan nilai kadar lignin dan selulosa relatif kecil. Kelarutan dalam NaOH 1 % berkisar 12,06-17,07 (KG) dan 11,85-20,79 % (KT), kadar abu sekitar 0,72-3,64 % (KG) dan 0,74-4,73 % (KT), sedangkan nilai pH berkisar 5,56-8,02 (KG) dan 7,09-7,96 (KT). Untuk sifat warna, kisaran nilai indeks kecerahan (L*), kemerahan (a*), dan kekuningan (b*) pada bagian gubal adalah 48-53, 6-11, dan 9-20, secara berturutan,, sedangkan pada bagian teras ABSTRACT This study was aimed at finding out the chemical and colour properties of keruing (Dipterocarpus humeratus), mersawa (Anisoptera laevis) and kapur (Dryobalanops keithii) timbers as their limited information up to now. Tree samples were obtained from Muara Wahau forest, East Borneo. Sapwood and heartwood then were cut from the base parts of the trees. Chemical examinations refered to ASTM standard. Colour measurements were performed through CIELAB coordinate system. The results of extractive measurements of 3 species showed that the amounts of ethanol-toluene extractive (ETE) ranged from 2.37-4.60 % in the sapwood (SW) and 2.58-4.81 % in the heartwood (HW), hot-water solubles (HWS) ranged from 2.14-6.49 % (SW) and 1.14-5.77 % (HW), then cold-water solubles (CWS) were 1.61-6.39 % (SW) and 1.06-3.26 % (HW). The tendency from sapwood to heartwood showed an increasing levels in ETE and decreasing in HWS and CWS. The measurement in the cell wall components showed that the contents of lignin ranged from 27.39-33.29 % (SW) and 25,77-34,19 % (HW), holocellulose ranged from 70.50-73.73 % (SW) and 65.94-74.84% (HW), as α-cellulose were 45.83-49.62 % (SW) and 44.23-52.32 % (HW). From sapwood to heartwood, a slight difference in lignin and cellulose levels were found. The solubility in NaOH 1 % levels were 12.06-17.07% (SW) and 11.85-20.79 % (HW), ash contents were 0.72-3.64 % (SW) and 0.74-4.73 % (HW), whereas the pH values ranged from 5.56-8.02 (SW) and 7.09-7.96 (HW). With regard to colour properties, the brightness (L*), redness (a*), and yellowness (b*) indexes in the sapwood were 48-53, 6-11, and 9-20, respectively. In the heartwood, the values were 40-49, 9-16, dan 14-18, respectively.