Laboratory wet milling of corn: Milling fraction correlations and variations among crop years

Several coproducts result from fractionating corn in the wet-milling process. Because small changes in product composition and milling characteristics can have a major impact on coproduct yields and values, testing is done to anticipate final product yields. Using small sample size and controlled conditions, a laboratory wet-milling method proved to be a useful tool for wet milling and genetics industries. A wet-milling process (100-g batches) was used for data collection. Data collected during 11 years (1994-2004) were observed for samples used as benchmarks to verify process precision and accuracy and determine correlations among wet-milling yields. More than 400 milling tests were performed on benchmark samples. Data from benchmark samples also were pooled. Coefficients of variation were low (<6%) for mean yields; year-to-year standard deviations of benchmark sample yield means were homogenous and implied precision of the procedure. Some differences were detected in mean yields among years (P ≤ 0.05) for benchmark data due to combined effects of hybrid and environment. A negative correlation (r = -0.58) was observed between starch and gluten yield for pooled benchmark data. Four years (2002-2005) of milling data from commercially available hybrids were analyzed using the milling procedure. For pooled commercial data, the correlation between starch and fiber yield was (r = -0.80); correlation between starch and gluten was (r = -0.76).