Near-infrared spectroscopy for monitoring starch hydrolysis

Near-infrared (NIR) spectroscopy has been evaluated for monitoring the acid -catalyzed hydrolysis (thinning) of starch. In practice, the extent of star ch hydrolysis is measured in fluidity units, which correspond to a physical property of the hydrolyzed starch material. NIR spectra of samples taken p eriodically during a series of starch-thinning reactions were used to predi ct fluidity. The standard error of prediction (SEP) was 1.06 mL with the us e of partial least-squares (PLS) regression in conjunction with digital Fou rier filtering. This SEP was significantly better than that reported before with a univariate calibration model based on the integrated area of the 44 00 cm(-1) (2272 nm) absorption band for carbohydrates. The improved SEP mee ts the industry demands for real-time monitoring. Although these calibratio n models were developed from samples prepared in the laboratory, no spectro scopic differences were apparent between spectra collected from these labor atory samples and spectra collected from samples taken directly from plant starch slurries during actual thinning reactions. This similarity in spectr al features, and hence chemical: matrix, supports the potential of NIR spec troscopy for on-line monitoring of industrial starch-thinning processes.