Microwave Assisted Extraction of Watermelon Rind Pectin with Different Kind of Acid Solution Indah Hartati # , Indah Riwayati # , Endah Subekti + # Department of Chemical Engineering, Faculty of Engineering, Wahid Hasyim University hartatiprasetyo@gmail.com, riway79@yahoo.com + Department of Agribusiness, Faculty of Agricultural, Wahid Hasyim University bekti_unwahas@yahoo.com Abstract — Watermelon biomass can be categorized as three main components which are the flesh, seed, and rind. Watermelon rind is the area of white-colored flesh between the colored flesh and the outer skin of watermelon. It is constituted approximately 13% of pectin, and made it as a potential raw material for pectin production. Therefore it is necessary to separate pectin of watermelon rind. Pectin can be separated from watermelon rind matrix by microwave assisted extraction (MAE). Commonly, pectin separation is conducted by subjected in an acid solution. The aim of this work was to investigated the utilization of different kind of acid solution in the microwave assisted extraction of watermelon rind pectin. The acid solution were hydrocloric acid, citric acid, acetic acid and sulphuric acid. The molarity of the acid solution was varied of 1 and 2 N. 20 grams of watermelon rind powder was subjected into 200 ml od acid solution. The mixture was then irradiated in microwave extractor for 15 minutes at 39,9W. The research showed that 1 N of sulphuric acid gave the highest yield of extraction, namely 18%. Key words - pectin, watermelon rind, MAE, sulphuric acid. I. INTRODUCTION The energy of the conventional heating process is transferred to the material by convection, conduction, and radiation phenomena through a thermal gradients. In contrast, the energy of the microwave heating is delivered directly to materials through molecular interactions with the electromagnetic field via conversions of electromagnetic energy into thermal energy. Energy transfer of the microwave heating occurs by two mechanisms: dipole rotation and ionic conduction [1, 2]. The unique properties of microwave have promote the application of microwave in various area. Microwave heating has been applied in various chemical synthesis, reactions, analysis and processes such as drying, sintering, and extraction [3]. In microwave assisted solvent extraction, the mass and the heat transfers occur from the inside of the extracted material to the bulk solvent In conventional heating, heat transfer occurs from the outside to the inside whilst mass transfer occurs from the inside to the outside [4]. Compared to conventional extraction, microwave assisted extraction (MAE) offers many advantages, including shorter extraction time, less solvent consumption, higher extraction rate and better product with lower cost because the microwaves heat the solvent or the mixture directly [5]. Due to its advantages, microwave assisted extraction has been applied in the separation of many phytoconstituents {4,5,6]. Pectin is one of them. Pectins are high molecular weight heteropolymers containing a majority of galacturonic acid units. The acid group may be free, a simple salt or naturally esterified with methanol. Pectins are also contain a range of neutral sugars, including rhamnose, galactose, arabinose and lesser amounts of other sugars. Pectin is present within the primary cell wall that hold cellulose together of almost all higher plants [7]. Because of its ability to form gels, pectin has important nutritional and technological properties. Pectin is having properties such as gelation and emulsion stabilization which make it useful in the manufacture of food, cosmetics, and medicine [8]. In food industry, pectin has been widely applied as thickening, gelling, stabilizer and emulsifying agent [8]. Pectin is used as a gelling agent in a wide range of fruit-based products. Pectin can be used to improve the mouth-feel and the pulp stability in juice based drinks and as a stabiliser in acidic protein beverages. Pectin also increases the gel strength of low calorie jams. Pectin is also used in confectionery jellies to give a good gel structure [9]. In medicine, pectin helps in lowering serum cholesterol level, removing heavy metal ions from the body, stabilizing blood pressure and restoring intestinal functions and weight reduction [10]. Pectin is also has been used potentially as a carrier for drug delivery to the gastrointestinal tract, such as matrix tablets, gel beads, film- coated dose form. Moreover, cosmetic product used pectin as stabilizer. Nowadays the major sources of pectin production are citrus peel and apple pomace. Alternative sources of pectin are continously investigated and developed, which one of them is watermelon rind. Watermelon biomass can be categorized as three main components which are the flesh, seed, and rind. Watermelon rind is the area of white-colored flesh between the colored flesh and the outer skin of watermelon. The rind of watermelon is reported to contain approximately 20% cellulose, 23% hemicellulose, 10% lignin, 13% pectin, 7 mg/g silica, and 12% silica free minerals [11]. -- Page 27 of 436 -- ICETIA 2014 ISSN 2407-4330