Mid-infrared Diffuse Reflectance Spectroscopy Research Articles

Mid-infrared Diffuse Reflectance Spectroscopy for Discriminant Analysis of Food Ingredients

The objective was to determine if mid-infrared diffuse reflectance spectroscopy could be used to discriminate various food ingredients. Samples (n = 106) consisting of buttermilk, cheese, dehydrated onion and milk-egg powders, wheat flours, and two powdered seasonings (cheese and ranch) were scanned as neat powders using diffuse reflectance on Digilab FTS-60 and Perkin-Elmer model 2000 Fourier transform spectrometers. Discriminant analysis, using mean centering and multiplicative scatter-corrected spectra, was performed using Mahalanobis distance by principal component analysis using the averaged predicted distance or F-test indicator to select factors obtained from a one-out cross-validation analysis. Results from the two spectrometers demonstrated that discriminant analysis of food ingredient powders based on spectra of neat powders can be successfully carried out. In general, it was found that results using 4-cm-1 resolution spectra were somewhat superior to those based on lower 16-cm-1 resolution spec...

Determination of Protein in Ground Wheat Samples by Mid-Infrared Diffuse Reflectance Spectroscopy

The objective of this study was to determine whether mid-infrared diffuse reflectance spectroscopy could be used in the same manner as near-infrared diffuse reflectance spectroscopy to quantitatively determine the protein content of ground wheat samples. One hundred and thirty hard red winter wheat samples were assayed for protein by combustion and scanned in the near- and mid-infrared. Samples (UDY ground) were scanned neat in the near-infrared from 1100 nm (9091 cm−1) to 2498 nm (4003 cm−1) on a scanning monochromator and in the mid-infrared from 4000 cm−1 (2500 nm) to 400 cm−1 (25,000 nm) on a Fourier transform spectrometer at 4-and 16-cm−1 resolutions. Protein content varied from a low of 8.98% to a high of 18.70% (average of 12.86% with a standard deviation of 1.66%). Calibrations developed with the use of partial least-squares gave an R2 and bias-corrected standard error of performance of 0.999 and 0.054 for the near-infrared and 0.997 and 0.085 for the mid-infrared (4 cm−1 resolution). Calibration results based on mid-infrared spectra, while not as good as those for near-infrared spectra, were nevertheless quite good. These results demonstrate that it is possible to develop satisfactory calibrations for protein in ground wheat with the use of mid-infrared spectra without the need for sample dilution with KBr.

Near versus Mid-Infrared Spectroscopy for Quantitative Analysis of Chlorite Treated Forages and By-Products

The objective of this work was to explore the relative merits of near and mid-infrared diffuse reflectance spectroscopy in determining the composition of sodium chlorite treated forages and by-products. Sixteen feed-stuffs (174 total samples treated at one of 11 levels of sodium chlorite, 0 to 0.394 g per gram of feedstuff) were examined in the near and mid-infrared spectral regions using diffuse reflectance on a Fourier transform spectrometer, and in the near infrared region using a grating monochromator. Samples were scanned as is and as 5% sample in KBr on the Fourier spectrometer and as is on the grating monochromator. Samples were analysed chemically and spectroscopically for neutral and acid detergent fibre, in vitro digestibility, permanganate lignin, crude protein and lignin nitrobenzene oxidation products. Results showed that diffuse mid-infrared reflectance spectroscopy can perform as well as, and sometimes better than, diffuse near infrared reflectance spectroscopy in determining the composition of chlorite-treated forages and by-products. In addition, Fourier near infrared spectroscopy did not perform as well as either near infrared using a grating monochromator or the Fourier mid-infrared spectrometer. Finally, diluting samples with KBr was often beneficial for mid-infrared based determinations.

Near- versus Mid-Infrared Diffuse Reflectance Spectroscopy for the Quantitative Determination of the Composition of Forages and By-Products

The objective of this work was to explore the relative value of near- and mid-infrared diffused reflectance spectroscopy in determining the composition of forages and by-products. Sixty-seven samples consisting of 15 alfalfa, 16 tall fescue and 15 orchard grass hays, 10 corn stovers and 11 wheat straws at various stages of maturity were examined by diffuse reflectance using a scanning monochromator (1100–2500 nm), a Fourier near infrared spectrometer (10,000–4000 cm−1, 4 and 16 cm−1 resolution, neat and 5% sample in KBr) and a Fourier mid-infrared spectrometer (4000–400 cm−1, 4 and 16 cm−1 resolution, neat and 5% sample in KBr). Samples were analysed chemically and spectroscopically for fibres, in vitro digestibility, crude protein, nitrobenzene oxidation products and various measures of lignin content. The results showed that diffuse mid-infrared reflectance spectroscopy can perform as well as, and sometimes better than, diffuse near infrared spectroscopy in determining the composition of forages and by-products. In addition, Fourier near infrared spectroscopy did not perform as well as either near infrared using a scanning monochromator or the Fourier mid-infrared spectrometer. Finally, diluting samples with KBr was not beneficial for either Fourier based determinations. Additional work with more diverse data sets and various Fourier instrument configurations will be needed to further define the limits and usefulness of Fourier transform near- and mid-infrared spectroscopy in the determination of forage and by-product composition.