Abstract
The order of reaction and reaction velocity constants were sought by comparing esterification velocity by adding dilute aqueous solutions of mono-, di- and trihydric aliphatic alcohols to different kinds of rice brans containing various degree of free fatty acid. Change in properties of fatty matter and its composition were also examined by adding aqueous solutions of either methanol or ethanol to a large quantity of rice bran. As a result it was found that the apparent ester formation reaction due to the addition of monohydric alcohol is in accordance with the secondary reaction and that the velocity is in the order of n-butanol_??_n-propanol>ethanol_??_methanol. As the dihydric alcohol ethylene glycol and 1, 3 butylene glycol were employed, and as the trihydric alcohol glycerin was used. In this case ester formation reaction velocity was in the order of ethylene glycol>1, 3 butylene glycol>glycerin and was only 1/51/10 of monohydric alcohol. Especially slow is the esterification velocity of glycerin.
Change in properties of the fatty matter due to the lapse of reaction time and its composition were examined by adding aqueous solution of 20wt% of either methanol or ethanol to a large quantity of rice bran. As a result the presence of about 50% methyl or ethyl ester was observed. From this result the possibility of high yield esterification was proved. It became apparent that the lipase which exists in rice bran performs the hydrolysis of fatty matter and that it carries out concurrently the ester synthesis of free fatty acid and monohydric alcohol.
