Application of near infrared reflectance spectroscopy to the compositional analysis of biscuits and biscuit doughs

The possible use of near infrared (n.i.r.) diffuse reflectance spectroscopy in the monitoring of automatic metering equipment used for fat, sucrose, dry flour and water in short dough biscuit production has been investigated. The experimental design involved randomisation of a standard pilot scale Lincoln biscuit recipe to produce calibration and prediction samples and comparison of n.i.r. results with the levels of ingredients determined from the recipe. The use of several strategies based on regression analysis for selection of the ‘best’ wavelengths for reflectance measurements for each analyte was investigated. A novel strategy based on computing the regressions on analyte concentration of all possible pairs of reflectance readings across the spectrum at given intervals is presented. The results of the experiments demonstrate that the precision of the n.i.r. method is excellent for all four constituents, but only the calibrations for fat are sufficiently accurate to be capable of detection of metering errors of ±5% relative to the total amount of fat in the recipe.