Rice bran oil extraction : a study on leaching kinetics and cross flow extraction

Abstract

Rice bran is the thin coating on the rice grain, exists between the rice grain and the rice husk. Rice bran which is a byproduct of the rice milling process is highly nutritious due to the presence of lipids, protein, minerals and vitamins. Rice bran oil has a high medicinal value and hence is used in many pharmaceutical manufacturing processes. Steam stabilized rice bran was pelletized to equivalent volume diameter of 8 mm and nee bran 01 was extracted from six rice varieties used in Sri Lanka using Iso propyl alcohol as the solvent. Results show that the rice bran contains 11 to 18 weight % oil for the types of bran tested. Three stage cross flow extraction experiments conducted for the selected types of bran show approximately 50% of the oil is extracted in the first stage followed by 30% and 20% of the oil extraction in the second and third stages respectively Extraction kinetic data were fitted to three kinetic models and model parameters were determined. Analysis of the results revealed that data fits to second order model, Weibull’s equation and power law model with correlation coefficients (R2) and root mean square (RMS) values in the range of 0.989 to 0.996 and ± 0.01x2 to ±0 05 respectively. Initial extraction rates predicted from the second order model were 0 052 min and 0.063 min and the difTusional exponent (n) in the power law model were 0.267 and 0.213 for bran types BG 35- and AT 307 respectively. Predicted maximum extraction yield from the second order equation and the scale parameter from the Weibull’s equation were in good agreement with the experimental results. Scale parameter (8) in the Weibull’s equation which represents the time needed to accomplish approximately 63% of the extraction were 54 and 60 mins for the two types of rice bran, BG 352 and AT 307, tested respectively. The kinetic data thus determined enables prediction of time required for extraction and hence the size of the extraction unit.