LB/3>on j' /oZ OPTIMAL OPERATING CONDITIONS & EQUILIBRIUM CHARACTERISTICS OF RICE BRAN OIL EXTRACTION M.Sc ( Chemical and Process Engineering ) N. C. Gangodavilage University of Moratuwa January, 2002 lk-Sk-1 0745-47 University of Moratuwa 74547 OPTIMAL OPERATING CONDITIONS & EQUILIBRIUM CHARACTERISTICS OF RICE BRAN OIL E X T R A C T I O N By N. C. Gangodavilage This thesis was submitted to the Department of Chemical and Process Engineering of the University of Moratuwa in partially fulfillment of the Degree of Master of Science in Chemical and Process Engineering Department of Chemical and Process Engineering, University of Moratuwa, Sri Lanka. January, 2 0 0 2 " I certify that this thesis does not incorporate without acknowledgement any material previously submitted for a degree or diploma in any University and to the best of my knowledge and belief it does not contain any material previously published, written or orally communicated by another person except where due reference is made in the text" Signature of the candidate (. N . C. Gangodavilage) " To the best of my knowledge, the above particulars are correct" Supervisor HACK rc\Sy Dr ( Mrs )B.M.W.P.K. Amarasinghe Head of the Department, Department of Chemical and Process Engineering, University of Moratuwa. A B S T R A C T Rice bran is the cuticle between the paddy husk and the rice grain and is obtained as a byproduct in rice processing. The bran contains 12-25 wt% oil and approximately 98% is extractable. Rice bran oil is a very important source o f oil, both as an edible oil and non-edible oil. The oil has high medicinal value, due to presence of anti-oxidants, anti-cancer agents, cholesterol reducing agents, skin improving agents, anti- dandruff and anti-itching agents. The oil can also be used for production o f soap, surfactants, cosmetic formulations, emulsifiers, textile auxiliaries, synthetic rubber products etc. In this work, extraction o f rice bran oil from various brands of rice bran available in Sri Lanka has been studied. Experiments were conducted using pilot plant scale leaching unit and the soxhlet apparatus to extract rice bran oil using hexane as the solvent. The key factors controlling the extraction have been identified. Results show that the bran obtained from parboiled paddy has a higher yield o f rice bran oil compared to the raw rice bran. Method o f bran pretreatment, extraction temperature, extraction time, pellet size and free fatty acid content are the factors affecting oil extraction. Comparison o f extraction results by various pretreatment methods shows an enhancement of oil extractability due to steaming. Analysis of the extracted oil shows that steaming is the most effective method o f bran pre-treatment with respect to the FFA content. Pelletization of bran provides easy percolation and avoids channeling o f the solvent and contamination of the oil from fine solids. Results show a decrease in extraction rate with time and this may be due to the fact that the solute has to diffuse from the interior of the pellet in the later stages of extraction. Extraction of rice bran oil using organic solvents was compared with aqueous extraction. The highest yield for aqueous extraction was obtained at 70 °C and pH 12. Refined and raw rice bran oil and commonly used vegetable oils were analyzed and the results were compared. Tie line and mass transfer data necessary for batch and continuous leaching equipment design were determined. A C K N O W L E D G E M E N T I am very much grateful to my supervisor Dr. (Mrs.) B. M. W. P. K. Amarasinghe, Head of the Department, Department of Chemical and Process Engineering, University of Moratuwa, for her great encouragement, guidance, dedication and patience paid through out the research. My Special word of thanks to Prof.(Mrs.) N. Ratnayake, Director, Post-Graduate Studies, University of Moratuwa and her staff for great support through out the project and Science and Technology Development project of Ministry of Science and Technology for their financial assistance . My special thanks to Mr. S.A.S Perera, Former Head of the department, Chemical And Process Engineering and Dr. Ajith de Alwis for their suggestions recommendations for research work and all members of academic staff, Mrs, Shantha Maduwage, Mr. Samarasinghe, of the Chemical and Process Engineering, University of Moratuwa. My Special thank to Mr. J. Wijesinghe and Mr. H.R. Saranelis Department of Chemical and Process Engineering, University of Moratuwa, for their great support through out the research. Also I would like to thank to technical and technical assistant staff of the department. My special thanks are due to Mr. Buddika De Silva, Miss. A.R.M.W.W.K. Ranasinghe, Miss. D.S.Liyanage, Mr. B.H.K.R.Sugahthadasa, J.G. Shanthasiri and other colleagues for their great support given me to complete my research successfully. Finally, my heartiest gratitude is for my family members for their great support given me through out the research C O N T E N T S List of figures List of tables Nomenclature Chapter I I N T R O D U C T I O N Chapter 2 R E V I E W O F R I C E B R A N & O I L E X T R A C T O N 2.1 Rice bran 2.1.1.1 Composition 2.1.2 Lipase activity 2.1.3 Enzyme kinetics of lipase 2.1.4 Enzyme activity at different conditions 2.2 Stabilization of rice bran 2.3 Extraction of oil 2.3.1 Separation by pressing 2.3.2 Solvent extraction of rice bran oil 2.3.2.1 Preparation of solid 2.3.2.2 Selection of solvent 2.3.2.3 Equilibrium data for solvent extraction 2.3.2.4 Modes of extraction 2.3.2.5 Diffusion of solvent through bran 2.3.3 Aqueous extraction 2.3.4 Use of super critical carbon dioxide 2.3.5 Rapid equilibrium extraction 2.4 Factors affecting extraction of oil 2.4.1 Effect of particle size on extraction 2.4.2 Pelletization of rice bran 2.5 Refining of extracted oil 2.6 Extraction of waxes 2.7 Nutritive value of rice bran oil 2.8 Edible rice bran oil 2.9 Non edible rice bran oil industry 2.10 Extraction of rice bran oil, a new industry to Sri Lanka Chap te r 3 E X P E R I M E N T A L M E A S U R E M E N T S 3.1 Determination of effect of method in stabilization 3.1.1 Stabilization of rice bran by hot air drying 3.1.2 Stabilization of rice bran by steaming 3.1.3 Fluidized bed drying 3.1.4 Solar drying t Page 3.1.5 Low temperature storage 36 3.1.6 Chemical stabilization 36 3.1.7 Comparison of methods of stabilization 37 3.2 Effect of moisture 37 3.2.1 Variation of FFA with moisture content 37 3.2.2 Variation of bran moisture content with time 38 3.2.3 Effect of relative humidity on free fatty acid content 38 3.3 Effect of pellet size 38 3.4 Effect of temperature on extraction 38 3.5 Effect of type of paddy 39 3.5.1 Free fatty acid content variation in parboiled and raw bran 39 3.6 Alternative solvents 40 3.6.1 Aqueous extraction 40 3.6.2 Rice bran oil extraction with Iso-propyl alcohol 41 3.7 Refining of oil 42 3.8 Determination of equilibrium compositions of rice bran oil extraction 42 3.9 Diffusion of solvent through rice bran pellets 43 3.10 Relationship between vapor pressure & boiling point of rice bran oil 43 3.1 1 Test methods for oil analysis 44 Chapter 4 4 R E S U L T A N D D I S C U S S I O N 51 4.1 Factors affecting rice bran oil extraction, using hexane as the solvent 5 1 4.1.1 Stabilization of rice bran 51 4.1.1.1 Stabilization by hot air drying 51 4.1.1.2 Stabilization by steaming 53 4.1.1.3 Stabilization by solar drying 55 4.1.1.4 Fluidized bed drying 56 4.1.1.5 Low temperature storage 56 4.1.1.6 Chemical stabilization 57 4.1.2 Comparison of effective stabilization process 58 4.1.3 Effect of moisture content 62 4.1.4 Effect of pellet size on extraction 65 4.1.5 Effect of extraction temperature 67 4.1.6 Effect of extraction time 68 4.2.1 Comparison of parboiled and raw bran 69 4.2.2 Varieties of rice bran 70 4.3 Alternative solvents 72 4.3.1 Aqueous extraction of rice bran oil 72 4.3.2 Iso propyl alcohol extraction of rice bran oil 75 4.4 Equilibrium characteristics of rice bran oil extraction 78 4.5 Diffusion of solvent through bran 85 4.6 Vapor pressure boiling point relation 4.7 Refining of extracted oil 86 87 Chapte r 5 5 Conclusions 92 References 95 Appendix I 100 Appendix I I 102 Appendix I I I 105 L I S T O F F I G U R E S Fig. No Figure Page Chapter 2 2.1 Layers of rice grain 4 2.2 Lipase activity in rice grain 6 2.3 Oxidative stability of rice bran oil 14 2.4 Representation of three component system on a triangular 15 Phase diagram 2.5 Phase diagram with no preferential adsorption of solvent 16 2.6 Phase diagram with preferential adsorption of solvent 16 2.7 Phase diagram for preferential adsorption of solute 16 2.8 Phase diagram showing different under-flow lines 17 2.9 Phase diagram for single stage operation 18 2.10 Phase diagram for counter current operation 21 Chapter 3 3.1 Semi-pilot scale leaching unit 49 3.2 Dynamic vapour pressure apparatus 50 Chapter 4 4.1 Stabilization of rice bran by hot air drying 52 4.2 Effect of hot air dryer bed height on variation of FFA 53 4.3 Stabilization of rice bran by steaming for different time periods. 54 x 4.4 Effect of steamer bed^height on stabilization of bran 54 4.5 Stabilization of rice bran by solar drying, 55 4.6 Fluidized bed drying for stabilization of rice bran 56 4.7 Low temperature storage of rice bran • 57 4.8 Chemical stabilization of rice bran by HC1 57 4.9 Comparison of effective method of stabilization of rice bran 59 4.10 Particle size distribution of rice bran 60 4.11 Extraction curves for treated rice bran 61 4.12 Effect of moisture content in bran on the FFA content of the bran 62 4.13 Variation of moisture content in bran during storage at room 63 temperature 4.14 Variation of moisture content in rice bran exposed to various 63 relative humidity 4.15 Equilibrium moisture content in rice bran at different relative 64 humidity 4.16 Effect of relative humidity on formation of FFA 64 4.17 Effect of pellet size on extraction 65 4.18 Effect of temperature on extraction 67 4.19 Effect of time on rice bran oil extraction 68 4.20 Rate of extraction of rice bran oil 69 4.21 Extractable oil percentages rice bran available in Sri Lanka 71 4.22 Effect of temperature on aqueous extraction of rice bran oil 73 xi 4.23 Effect of pH on aqueous extraction 73 4.24 Rate of aqueous extraction of rice bran oil 4.25 Effect of bran to water ratio in aqueous extraction 4.26 Effect of solvent to bran ratio for extraction of rice bran oil, with 1PA 4.27 Effect of temperature on IPA Extraction of rice bran oil 4.28 Effect of time on extraction of rice bran oil with IPA 4.29 Equilibrium compositions in leaching of parboiled rice bran 4.30 Equilibrium compositions in leaching of raw rice bran oil 4.31 Equilibrium compositions of rice bran Bg 400-1 4.32 Tie-line compositions of parboiled rice bran oil extracted with hexane ( fig 4.32- a,b,c,d) 4.33 Tie-line compositions of raw rice bran oil extracted with hexane (fig. 4.33-a,b,c) 4.34 Raffinate compositions of rice bran oil extracted with hexan 4.35 Triangular equilibrium diagram 4.36 Rate of solubility of rice bran oil 4.37 Boiling point curve for Rice bran oil 4.38 HPLC diagram of rice bran oil extracted with water 4.39 HPLC diagram of rice bran oil extracted with hexane 4.40 Visible absorption spectrum of rice bran oil 4.41 ASTM distillation curve for rice bran oil L I S T O F T A B L E S Table No. Title Page Chapter 2 2.1 Composition of rice bran 5 Chapter 3 3.1 Relative humidity of saturated salts 48 Chapter 4 4.1 Effect of pellet size on extractability .. 65 4.2 Efficiency of extraction with varying voidage 66 4.3 Effect of temperature on extractability 67 4.4 Rate of formation of FFA in parboiled and Raw bran 70 4.5 Varieties of rice bran 71 4.6 Effective solvent ratio for IPA extraction of rice bran oil 75 4.7 Oil extractability at different temperatures 76 4.8 Effect of time on extraction of rice bran oil with IPA 77 4.9 Equilibrium compositions of parboiled rice bran 78 4.10 Equilibrium compositions of raw rice bran 79 4.11 Equilibrium compositions Bg 400-1 rice bran 80 4.12 Characteristic analysis of rice bran oil 87 4.13 Fatty acid compositions of refined rice bran oil 88 xi N O M E N C L A T U R E AJ - a rea of solid liquid interface A -solute A O C S - American oil chemist association A S T M - American Standard Testing Methods C - concentration of the solute in the bulk of the solution C* - concentration of the solute at the surface of the solid Co - initial concentration of solute in the solution D - inert or solid phase D c o - Diffusion coefficient DOB - deoiled bran dt - change in time dw - change in mass E - extract Ef - Weight faction of extract F - feed FFA - free fatty acids IPA - isopropyl alcohol Kco - mass transfer coefficient N - normality ppm - parts per million R -raffinate RBO - rice bran oil Rf - Weight faction of raffinate Rh - relative humidity rpm - Rounds per minute S -Solvent SCC - Supercritical Carbon Dioxide Sf - Weight faction of solvent t - t ime V - volume Xf - Weight faction of Feed p s _ reduced density xiv