Standardization of Solvent Type and Extraction Time for Lipid Extraction From Brewers' Spent Grain (BSG) by Soxhlet Method.

Brewers' spent grain (BSG)'s potential use as a food ingredient is being evaluated, and thus, an accurate characterization of its proximate composition, particularly lipids, becomes essential. While the Soxhlet method is a widely recognized official standard test used for lipids measurement in food products, inconsistencies in solvent selection have led to variable and often no comparable results across studies. This is the first study that attempts to address that gap by systematically evaluating the impact of solvent type and extraction time on lipid yield from BSG. Five solvents and solvent mixtures, including acetone, ethanol, hexane, petroleum ether, and n-hexane, were used for lipid extraction. In the initial phase, 5 g BSG was extracted using 125 mL of various solvents over 5 h. Lipid yields from BSG varied from 4.54% to 8.44% depending on the solvent type, in which ethanol yielded the highest lipid content. Based on these results, ethanol was selected for further studies on the effect of extraction time. Soxhlet extractions were performed using ethanol and it's binary mixtures with hexane and n-hexane for 3, 5, and 7 h. The lipid yield from BSG varied from 7.66% to 8.44%, while the statistical analysis indicated no significant difference in lipid yield across the time range under studied conditions. Based on the findings from the study, it is recommended to use ethanol as a single solvent for 3-h extraction, as the method balances efficiency and resource use. The results from this study is beneficial for the laboratories to choose the proper solvent and extraction time for measuring lipids in BSG using the Soxhlet method.