Removal of Higher Fatty Acid Esters from Taiwanese Rice-Spirits by Nanofiltration

Abstract

The amounts of the three higher fatty acid esters (ethyl palmitate, ethyl oletate, and ethyl linolenate) in rice spirit were significantly decreased, over 65 % through nanofiltration (NF) with DK or DL membranes, compared to the 26–42 % reduction observed for an ultrafiltration membrane. The molecular weight cut-off was the main factor for the removal of the higher fatty acid esters. In addition, the rejection rates were increased with operating pressures; 60 psi was the most suitable pressure for the NF system. Not less than 80 % of higher fatty acid esters could be removed by the DK membrane under 60 psi pressure at 4 °C; only slight changes in physicochemical indices, including the ethanol concentration, flavor, and total acidity were observed for rice spirits following the NF treatment. On the other hand, the fusel alcohols in the treated-rice spirits were simultaneously decreased from 4.5 to 2.5 g/L (reaching the Chinese National Standard, below 3.3 g/L) and the product achieved a higher score in color via sensory evaluation. We anticipate a practical application of non-heat processes, such as NF, in Taiwanese rice spirits production due to the quality improvement achieved thereby.