Near Infrared Spectroscopic Determination of Moisture Content in Foods: Extraction Method by Organic Solvents

Abstract

In order to get a common NIR calibration equation which can be adapted to the determination of moisture content in various types of foods, we have tried to develop a water extraction method from foods by organic solvents. We used various starches and powder foods as the model. NIR spectra of various solvents containing water showed a clear band due to water around 1930 nm. Of the solvents used, this band in N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) systems was not shifted by the change of the moisture content. Then, the moisture was extracted from starch by these solvents. Approximately 60% was consistently recovered in a single-step extraction by DMA or DMF. The extraction by DMSO was too viscous to handle. The calibration equation was developed from the results for the extraction from starch by DMA. Then, moisture contents of powder foods were predicted using the calibration equation. For six of eight foods, good correlations were obtained between the laboratory values and the predicted values. These results suggest that this NIR method coupled with extraction is useful for the determination of moisture content with a common calibration equation for various kinds of foods.