Free Fatty‐Acid Generation and Lipid Oxidation during Dry‐Grind Corn Ethanol Fermentation

Abstract

The formation of free fatty acid (FFA) is an undesirable change during dry-grind corn ethanol fermentation because it negatively affects biodiesel transformation. The primary objective of this work was to determine where in the process FFA is generated using laboratory-scale simulation experiments. TLC and GC were used to quantify FFA in the extracted total lipids. Values obtained from FFA determination by titration were also compared with those obtained from TLC-GC. Results indicate that FFA generation is due to an incremental increase at each step in the process, particularly at the early slurrying and liquefaction stage, and also likely during the continuous backset. Furthermore, laboratory-based fermentations indicate that the oxidation of linoleic acid in the FFA fraction and possibly in the oil increased the FFA level determined using the titration method. Industrial oil samples collected were shown to be highly oxidized and this led to an overestimation of FFA by 15-24% using the titration method compared to TLC-GC due to the formation of a secondary oxidation product, acids. Such a discrepancy in FFA quantification and the level of lipid oxidation have not been seen in the literature. Keywords Free fatty acid (FFA) Á Corn ethanol fermentation Á Distiller's dried grains & solubles (DDGS) Á Distiller's corn oil (DCO) J Am Oil Chem Soc (2018) 95: 1521-1533.