|Peiris, Kamaranga H -|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 13, 2011
Publication Date: January 1, 2011
Repository URL: http://naldc.nal.usda.gov/download/49295/PDF
Citation: Peiris, K.S., Dowell, F.E. 2011. Determining weight and moisture properties of sound and fusarium-damaged single wheat kernels by near infrared spectroscopy. Cereal Chemistry. 88(1):45-50. Interpretive Summary: Moisture content (MC) is an important trait in grain quality evaluation. The MC of grain is usually expressed as a percentage of moisture based on wet weight or dry weight of kernels. Other quality traits such as starch, protein, oil contents are then expressed relative to MC. Near infrared (NIR) spectrometric techniques are often used to measure traits, but NIR spectra are affected by the mass of a constituent, which may not be related to the percentage of the constituent being measured. This may particularly be a problem when measuring traits in single kernels which can vary significantly in size. Thus a small kernel and large kernel can have the same percentage of water, but the mass of water can be quite different. We are developing single kernel techniques to assess Fusarium damage and to estimate deoxynivalenol contents of wheat grain samples affected by Fusarium head blight (FHB). Such grain samples are quite heterogeneous in terms of kernel size, weight and other chemical and physical properties. The results of this study showed that single kernel MC as well as fresh or dry weight and water mass of kernels could be predicted by NIR spectroscopy. Therefore, in single kernel analysis it is important to express quality traits such as MC in terms of mass/kernel basis rather than percentage basis. When the fresh weight of the kernel can be provided, the water mass of kernels could be accurately estimated by using predicted MC. This concept of measuring the mass of a constituent may also help in measuring traits like starch quality and protein quality where the mass of starch or protein must first be measured.
Technical Abstract: Single kernel moisture content (MC) is important in the measurement of other quality traits in single kernels since many traits are expressed on a dry weight basis, and MC affects viability, storage quality, and price. Also, if near-infrared (NIR) spectroscopy is used to measure grain traits, the influence of water must be accounted for since water is a strong absorber throughout the NIR region. The feasibility of measurement of MC, fresh weight (FW), dry weight (DW) and water mass (WM) of single wheat kernels with or without Fusarium damage was investigated using two wheat varieties with three visually selected classes of kernels having Fusarium damage and a range of MC. Calibration models were developed either from all kernel classes, or from only sound kernels of one variety which were then validated using all spectra of the other variety. A calibration model developed for MC when using all kernels from the wheat variety Jagalene had a coefficient of determination (R2) of 0.77 and standard error of cross validation (SECV) of 1.03%. This model predicted the MC of the wheat variety 2137 with R2=0.81 and a standard error or prediction (SEP) of 1.02%. Calibration models developed using all kernels from both varieties predicted MC, FW, DW, or WM in kernels better than models that used only sound kernels from both varieties. Single kernel WM was more accurately estimated using the actual FW of kernels and MC predicted by calibrations that used all kernels or sound kernels. The necessity to evaluate and express constituent levels in single kernels in mass/kernel basis rather than the percentage basis was elaborated. The need to overcome the effects of kernel size and WM on single kernel spectra before using in calibration model development was also highlighted.