Measurement of Plumpness for Intact Sunflower Seed Using Terahertz Transmittance Imaging

Abstract

The quality of sunflower seed usually influences the load and product quality. The plumpness, expressing as the percent of the kernel and shell (%), is a crucial indicator reflecting the vigor of the sunflower seed. Investigations were carried out to measure the plumpness of intact sunflower seed by the use of terahertz (THz) transmittance imaging. The THz data of the worms, defects, and sound sunflower seeds were scanned using a THz time-domain transmittance imaging system. Followed THz imaging, the shell and kernel of the sample were separated carefully and recorded RGB images as the reference. Compared with the shell, the absorption coefficients and time domain signals of the kernel showed a significant difference in 0.5–2.0 THz. The characteristic images in 0.5–2.0 THz and control groups of 0.5–1.0, 1.0–1.5, and 1.5–2.0 THz were extracted, and the defects, kernel, and shell could be discriminated clearly in 0.5–2.0 THz. The models of the plumpness were developed between the THz and RGB images processed by the threshold segmentation. The determination coefficient and root mean square error of prediction (RMSEP) were 0.91 and 4% for an independent prediction set, respectively. The results suggested that use of THz transmittance imaging in measurement of plumpness of the intact sunflower seed was feasible. In addition, THz imaging provided a novel quality assessment solution for the coated samples.