Technical note: a near-infrared reflectance spectroscopy technique to predict particle size of starch within corn silage

Starch particle size characteristics of 81 diverse corn silage samples, which included 27 combinations of hybrid, planting dates, and harvest dates subjected to 3 different degrees of kernel processing, were determined via vertical shaking through 9 screens with nominal square apertures of 19.0, 13.2, 9.5, 6.7, 4.75, 3.35, 2.36, 1.18, and 0.6 mm and a pan. Starch content of dry matter remaining on each screen and on the pan for each corn silage was determined, and geometric mean particle size (GMPS, μm), starch particles(SP)/g, starch surface area (SSA, cm²/g), kernel processing score (KPS), % starch < 4.75 mm, and the percentage of total starch remaining on each screen of the vertical shakers were calculated. Near-infrared reflectance spectra were obtained by scanning 3 types of samples: 1 mm of dried ground corn silage; whole undried, unground corn silage; and undried, unground corn silage that passed through a 19-mm screen. Calibrations to predict GMPS, SP, SSA, and KPS characteristics of corn silage starch were attempted from each spectral origin. Calibrations to predict GMPS, SP, SSA, KPS, and the percentage of total starch retained on screens of the vertical shaker was unattainable (R² < 0.45) using spectra obtained from 1 mm of dried ground corn silage or whole undried, unground corn silage. However, reasonable near-infrared reflectance spectra equations (R² > 0.81) for GMPS, SSA, and KPS were attained using spectra from undried, unground corn silage that passed through a 19-mm screen. This technique holds promise as a rapid and efficient method to determine particle size characteristics of starch within corn silage.