THE APPLICATION OF NEAR-INFRARED REFLECTANCE SPECTROSCOPY TO MEASURE THE DEGREE OF PROCESSING IN EXTRUSION-COOKING PROCESSES

NIR spectroscopy has previously been used to study structural changes in starch during the ageing of bread. In the present work, carried out under the Measurement & Testing Programme of the European Commission, this concept has been extended to measurement of starch structure in the products of twin-screw extrusion cooking of cereals. A range of pr ocessing conditions was devised to provide increasing levels of SME fo r the starch and a fairly constant residence time within the high temp erature shearing zone on the screws. Thus, SME was used as the depende nt variable against which NIR data were calibrated. A correlation coef ficient of 0.99 and standard error of calibration of 11 kJ/kg were ach ieved on products based on wholemeal wheat flour: This result was vali dated using an independent set of samples with a standard error of pre diction of 16 KJ/kg. A spectral interpretation was achieved by studyin g the spectral pattern associated with the prediction equations.