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AACC International Approved Methods - AACC Method 39-00.01. Near-Infrared Methods -- Guidelines for Model Development and Maintenance

AACC International Approved Methods

Infrared Analysis

AACCI Method 39-00.01
Near-Infrared Methods -- Guidelines for Model Development and Maintenance


This guideline provides general information on near-infrared (NIR) model development, performance evaluation, and calibration transfer to instruments of like brand. NIR spectroscopy, applied to the analysis of constituents in cereals, is popular for reasons of simplicity of operation, throughput, objectivity, and accuracy. The absorption response by overtone and combination frequencies of O-H, C-H, and N-H molecular vibrations, abundant in biological matter, allow samples to be analyzed. These signals are discernible by photometric detectors, which inherently have a very high signal-to-noise response. With the aid of a computer for postprocessing, the composition of cereals can be determined from NIR spectra, in terms of the contents of protein, carbohydrate, moisture, lipid, and other constituents. NIR quantitative analysis is a secondary procedure. Linear and nonlinear (less often) regression modeling is used to relate NIR readings to chemical concentrations determined by conventional reference methods. As such, the robustness and accuracy of an NIR model are strongly dependent on the samples chosen for calibration development, on the accuracy of the reference methods, and on the calibration procedure itself.