STUDI PENGARUH RASIO REAKTAN, pH, DAN WAKTU REAKSI TERHADAP SIFAT FISIKOKIMIA TEPUNG GADUNG (Dioscorea hispida Dennst.) TERASETILASI

Abstract

Abstrak

Tujuan dari penelitian ini adalah untuk mengetahui pengaruh rasio reaktan, pH  dan waktu reaksi terhadap nilai swelling power, solubility, dan derajat substitusi tepung gadung terasetilasi. Asetilasi dilakukan dengan mendispersikan 20 gram tepung gadung ke dalam 100 mL akuades. pH diatur hingga nilai tertentu (8, 9, dan 10) dengan penambahan NaOH 1 M. Slurry diaduk selama 30 menit. Setelah itu, asam asetat dengan rasio tertentu 1:3, 1:4, dan 1:5 (berat asam asetat:berat tepung) ditambahkan secara perlahan ke dalam campuran reaksi. pH campuran dijaga ke kondisi awal dengan penambahan NaOH 1 M. Reaksi asetilasi dibiarkan berlangsung selama waktu tertentu (10, 20, 30, 40, 50, dan 60 menit,) kemudian dihentikan dengan penambahan HCl 1 M sampai pH 5,5. Tepung terasetilasi disaring dan dicuci dengan air suling sebanyak tiga kali pencucian dengan rasio berat pencucian 1:3 (b/v). Tepung terasetilasi dikeringkan pada suhu 50^oC sebelum dianalisa nilai daya kembang, kealarutan, dan derajat substitusinya. Hasil penelitian menunjukkan bahwa, kondisi optimal diperoleh pada tepung yang dimodifikasi dengan rasio reaktan 1:3, pH 8, dan waktu reaksi 30 menit, dengan nilai swelling power,solubility, dan derajat substitusi sebesar 7,3 g/g; 18,6 %; dan 0,033.

kata kunci :gadung, asetilasi, swelling power, solubility, derajat substitusi

Abstract

The objective of this research are to investigate the effect of glacial acetic acid:flour mass ratio, pH, and reaction time on the swelling power, solubility,and degree of substitution acetylated gadung tuber flour. The acetylation was carried out by dispersing 20 grams of gadung flour in 100 mL distilled water. The pH of the dispersed system was adjusted to a certain value (8, 9 or 10) by adding of 1 M NaOH.  Then, the predetermined mass of glacial acetic acid (1:3, 1:4, and 1:5)  was added to the reaction mixture. The pH was brought back to the initial condition by adding of 100 mL 1 M NaOH. The acetylation reaction was let to occur for 10 to 60 minutes before it had been terminated by adding 1 M HCl until pH 5,5. The acetylated flour were obtained by filtration of reaction mixture. It is followed by threefold washing that used distilled water with 1: 3 (w/v). The acetylated flour then were dried in an electric oven at 50^oC before analyzed to swelling power, solubility, and degree of substitution. Based on the value of swelling power and water solubility of acetylated gadung tuber flour were obtained, the best reaction condition were the ratio of glacial acetic acid/gadung tuber flour 1:3, pH 8, and the reaction time of 30 minutes with swelling power 7,3 g/g; solubility 18,6%, and degree of substitution 0,033.

key words : gadung, acetylation, swelling power, solubility, degree of substitution