CLASSIFICATION OF NORMAL AND AGED SOYBEAN SEEDS BY DISCRIMINANT-ANALYSIS USING PRINCIPAL COMPONENT SCORES OF NEAR-INFRARED SPECTRA

Near infrared transmittance spectra of normal and aged soybean seeds w ere measured using a specially designed sample cell for a single seed and were analysed by Principal Component Analysis (PCA) and Discrimina nt Analysis (DA) using PC scores for the classification of normal seed s and aged seeds. Soybean seeds were acceleratedly aged under an ambie nt condition of 42 degrees C and 98% RH for 3, 5 or 7 days. As control some other seeds were also stored under condition of 15 degrees C and 98% RH for 7 days, preserving the ability to germinate. After these t reatments the seeds were dried at room temperature till they become in itial water content. In multiplicative scatter corrected (MSC) spectra between normal and aged seeds somewhat changes were observed. The log (1/T) at 990 nm decreased with the increment of ageing days, while th e log (1/T) at 1010 nm increased to the contrary. Aged seeds (7 days) were clearly separated from control using on the plane with the axes o f second (PC 2) and third (PC3) principal components, derived from PCA of MSC spectra. The results of DA using 2PC scores (PC2 and PC3) whic h were effective to separate aged seeds, showed that 60% of aged seeds for 3 days, 80% of aged seeds for 5 days and 100% of aged seeds for 7 days were correctly classified. Phospholipids content in soybean seed s decreased with ageing, and then became half after 7 days, while tota l lipids content was constant. The loading plot for PC3 were similar t o the spectrum of lipids, suggesting that PC3 reflected the changes of phospholipids during ageing. Consequently, it was concluded that NIR spectroscopy had a possibility for classifying normal and aged soybean seeds, and that the change of phospholipids content was an important factor for this classification.