Impact of sample preparation on the determination of crude fat content in corn

摘要

Sample preparation is an important step in any analysis as it directly affects the assay results. The effect of sample preparation on the extraction of crude fat from 10 corn samples with varying fat content was studied. Samples were ground on seven different grinders, namely, the Mega-grinder, Knifetec, Cyclotec, Cemotec, Mikro-mill, UDY, and Brinkmann-Retsch mill. The crude fat was extracted from ground samples using Soxtec and/or Butt-tube extraction procedures and was determined gravimetrically after evaporation of the extraction solvent. The lowest amount of crude fat was extracted from samples ground on a Cemotec grinder. However, similar yields of crude fat were obtained with the other six sample preparation mills by using the proper screen size and grinding conditions. We observed an increase of 0.3% in the grand mean of crude fat extracted from samples ground on a Cyclotec grinder fitted with a 1.0-mm screen as compared with a 2.0-mm screen. Modifying the grinding time from 5 to 10 s/cycle and increasing the number of cycles from 2 to 3 resulted an increase of 0.4% in the grand mean of crude fat extracted from 10 corn samples. No significant differences were observed in crude fat content when samples were ground with a Monsanto-built Mega-grinder, located at two different sites. The efficiency of crude fat extracted from ground samples was found to increase with the decrease in particle size.