CHEMISTRY & CHEMICAL TECHNOLOGY Chem. Chem. Technol., 2018, Chemical Vol. 12, No. 1, pp. 101–108 Technology ACID HYDROLYSIS AND ETHANOL PRECIPITATION FOR GLUCOMANNAN EXTRACTION FROM CRUDE PORANG (AMORPHOPHALLUS ONCOPHYLLUS) TUBER FLOUR Andri Kumoro 1, * , Tunjung Yuganta 1 , Diah Retnowati 1 , Ratnawati Ratnawati 1 https://doi.org/10.23939/chcht12.01.101 Abstract. 1 Extraction of glucomannan from crude porang flour by acid hydrolysis and ethanol precipitation was studied. Effects of acid concentration, temperatures and time were investigated, kinetics model of the process was developed and the parameters were evaluated based on experimental data. New data on yield and purity of glucomannan under various conditions were obtained. Keywords: glucomannan, extraction, acid hydrolysis, modeling, mass transfer, kinetics. 1. Introduction Glucomannan is one of the neutral polysaccharides that is composed of β-1,4 linked D-mannose and D-glucose with the molar ratio of mannose and glucose of about 1.6:1. The backbone structure is lightly branched (an approximate degree of branching of 8 %), with short side branches at the C-3 position of the mannoses [1]. The chain has 5–10 % acetyl group substitutes located at every 9 to 19 sugar units, which is believed to play important role in the solubility and gelling properties [2]. Being an amorphous polymer the average molecular weight of glucomannan ranges between 10 5 and 10 6 g/mol [3]. According to Yao-Ling et al. [4] glucomannan has been used in traditional Chinese medicine for millenniums for the healing of asthma, cough, hernia, breast pain, burns, and skin disorders. Further, recent clinical studies have revealed the potentials of glucomannan to reduce blood sugar, lower blood cholesterol, control body weight, and promote healthy microflora in intestinal [5]. Due to biodegradability and good gel-forming ability, glucomannan is also widely used in the pharmaceutical field for controlled release drug delivery system [6]. In addition, due to its specific rheological and gelling properties, glucomannan is also abundantly used in food 1 Diponegoro University Prof. H. Soedarto, SH Road Tembalang, Semarang, Indonesia 50275 * andrewkomoro@che.undip.ac.id Kumoro A., Yuganta T., Retnowati D., Ratnawati R., 2018 and beverage industries as emulsifying and stabilizing agent for various food, drink, and cosmetic products [4]. Although glucomannan can be acquired from various botanical sources, the tuber of porang (Amorphophallus oncophyllus) plant, which belongs to the Aracea family, has been found to be the most potential source in view of its high glucomannan content and sustainable availability [7]. Generally, fresh porang tuber may contain 8–10 wt % of glucomannan [2]. Prior to the extraction of glucomannan, the porang tuber is washed, sliced, dried and milled; and the porang tuber flour (PTF) of refined powder is further separated by wind shifting. The glucomannan content in the crude porang tuber flour (CPTF) usually ranges from 50 to 70 wt % [8], whereas purified porang tuber flour (PPTF) should have glucomannan content of no less than 90 wt %. The impurities trapped in CPTF particles are usually coming from the tissue space [4], which mainly comprises starch, lipid, protein and ash [2]. As the main impurity, the starch may seriously affect the purity and quality of glucomannan, such as reducing viscosity and increasing turbidity [9]. High-quality porang flour can be obtained through separation of glucomannan granules from the smaller starch granules by conventional dry or wet processing. The dry process method includes grinding of dried porang tuber chips into CPTF, which is later purified via wind- sifting [10]. Unfortunately, porang flour obtained using this method is of low purity and is therefore sold as a low- price food commodity [11]. To overcome this problem, a number of wet extraction methods have been developed to extract glucomannan from CPTF, such as enzymatic hydrolysis [12, 13], dialysis and ethanol precipitation [14], washing with water, aqueous alcohol [15] and benzene- ethanol solution [16], high energy centrifugation [8], or a combination of the aforementioned methods. Unfortunately, most of those processes are complicated; require higher operating cost and sometimes still result in low yield and product purity. Therefore, it is apparent that development of more efficient methods is needed to substitute the existing ones.