N: Nanoscale Food Science JFDS jfds˙1492 Dispatch: 12-22-2009 CE: PMS Journal MSP No. No. of pages: 5 PE: Marie 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 JFS N: Nanoscale Food Science, Engineering, and Technology Develop a Novel Method for Removing Fusel alcohols from Rice Spirits Using Nanofiltration CHANG-WEI HSIEH,YI-HSIANG HUANG,CHENG-HUNG LAI,WAI-JANE HO, AND WEN-CHING KO ABSTRACT: The removal effect on excessive fusel alcohols from rice spirits were investigated using nanofiltration (NF) and ultrafiltration (UF). Compared to UF (GE and GH membranes), NF (DK and DL membranes) showed 10 times greater effect for fusel alcohols rejection due to molecular weight cut-off. On operating pressures, 488.95 kPa was suitable with a rejection rate attaining 44.2% for DK membrane. Only slight changes in physicochemical indices including ethanol concentration, flavor, total acidity, pH value, and soluble solid content were observed for rice- spirits after NF treatment. Moreover, rice spirits treated with the DK membrane achieved a higher score in sensory evaluation. We anticipated a practical application of the nonheat processes in rice spirits production. Keywords: fusel alcohols, nanofiltration, quality, rice spirits, ultrafitration Introduction F usel alcohols are byproducts of the ethanol distilling of a mixture of several alcohols (Kujawski and others 2002). Al- cohols with 2 or more carbon atoms are generally known as higher alcohols, or fusel alcohols (Huckenbeck and Bonte 2003; Lachenmeier and others 2008). The fusel alcohols in rice spir- its are mainly composed of propan-1-ol, butan-1-ol, 2-methyl-1- propanol, and 3-methyl-1-butanol (Lachenmeier and others 2008). The fusel alcohols produced in the fermentation process of wine are mainly composed of 2-methyl-1-butanol, 3-methyl-1-butanol, 2-Methylpropan-1-ol, propan-1-ol, 4-(2-Hydroxyethyl) phenol, 1- hexanol, and 2-phenylethanol (Regod´ on Mateos and others 2006). Although fusel alcohols give rice spirits its special flavor, exces- sive concentration can cause nervous hyperemia, dizziness, and headaches in consumers, and produce spirits with a bitter, astrin- gent taste, or turbid (or cloudy) appearance (Greenshields 1974; Li and others 2006; Lachenmeier and others 2008). The traditional method of reducing fusel alcohols content involves rigid control of the brewing process, such as selecting raw materials with low protein content, using yeast with low activity protease, and con- trolling the ambient temperature during brewing. However, these physical methods are seldom used to remove fusel alcohols, except for active carbon adsorption and resin adsorption, which are inef- fective and time-consuming methods (Cao 2006; Zhang and others 2006). The brewing industry has used membrane filtration for many years, but it is only used to remove impurities in alcohols. In 1992, the process of nanofiltration (NF) was developed based on pressure-driven liquid separation and condensation procedures (Majumdar and Sirkar 1992). The molecular weight cut off (MWCO) (150 to 1000 Da) of NF is within the nanometric scale, between reverse osmosis (RO) and ultrafiltration (UF) (Murthy and others 2005). Since NF can be performed at room temperature, it can MS 20090664 Submitted 7/11/2009, Accepted 11/4/2009. Authors Hsieh and Ho are with Dept. of Medicinal Botanicals and Health Care, Da-Yeh Univ., 168 Univ. Rd, Dacun, Changhua 51591, Taiwan, Republic of China. Au- thors Huang, Lai, and Ko are with Dept. and Graduate Program of BioIn- dustry Technology, Da-Yeh Univ., 168 Univ. Rd, Dacun, Changhua 51591, Taiwan, Republic of China. Direct inquiries to author Ko (E-mail: wel- son6404@hotmail.com). be used to protect heat-sensitive and volatile substances. When applied to alcohols, NF maintains the quality of alcoholic drinks (Banvolgyi and others 2006). It is energy-efficient because it can be performed under relatively low pressures (Koˇ suti´ c and others 1998). In recent years, NF has been widely applied to drinking water pro- cessing, food fermentation, medicinal condensation, and wastew- ater treatment (Koˇ suti´ c and others 1998; Tessier and others 2005; Banvolgyi and others 2006). Although some NF and UF literature is available, specific infor- mation regarding the application of NF and UF to remove fusel alcohols from rice spirits is limited. The present study is the 1st at- tempt to remove fusel alcohols from rice spirits using NF and UF under low temperature conditions (4 ◦ C). This study investigated the optimal operating pressure conditions (206.85 to 620.55 kPa) and evaluates the efficacy of fusel alcohols removal by NF and UF. The purpose of this study is to reduce the fusel alcohols content of rice spirits without affecting its quality and, ultimately, to improve rice brewing techniques. Materials and Methods Materials and components An FT-150P membrane filtration system was composed of the FLOJET Duplex Diaphragm Demand Pump (Model 2130-032, U.S.A.) and membrane module. Four types of spiral-wound mem- branes, including the DK (DK1812C-47P, GE Osmonics, MWCO 150 to 300 Da) and DL (DL1812C-47P, GE Osmonics, MWCO 150 to 300 Da) NF membranes, and the GE (GE2012C-28D, GE Osmonics, MWCO 1000 Da) and GH (GH1812C-47P, GE Osmonics, MWCO 2500 Da) UF membranes were used. These membranes were Q1 purchased from Advanced Biotechnology Consultant Co. Ltd. (Taipei, Taiwan). Mold and yeast cultures were purchased from the Food Industry Research and Development Inst. (Hsinchu, Taiwan). All other materials include ethyl acetate (Mallinckrodt, USA), 3-methyl-1-butanol (Katayama Chemical, Japan), and 2- methyl-1-propanol (Osaka, Japan) used in this experiment were of an analytical grade, and obtained commercially. Fermentation of Rice into Rice Spirits Rice spirits was made with a 1 : 1 ratio of rice grains (10 kg) and water (10 kg). The rice/water mixture was simmered at 125 ◦ C C  2009 Institute of Food Technologists R  Vol. 00, Nr. 0, 2009—JOURNAL OF FOOD SCIENCE N1 doi: 10.1111/j.1750-3841.2009.01492.x Further reproduction without permission is prohibited