Extending the use of visible/near-infrared reflectance spectrophotometers to measure colour of food and agricultural products

Three visible/near-infrared reflectance (VNIR) spectrophotometers (same manufacturer and model) were used to measure L*a*b* colour values for 50 food and agricultural products including spices and seasonings (e.g. tumeric, mustard, chili powder, salt), ground coffee, dessert powders, small seeds (e.g. canola, poppy, lentil), semolina, cornmeal, wheat flour, powdered cheese, drink crystals, soup mix, and ground breakfast cereal. The L*a*b* values were calculated from the visible spectral data as defined by the Commission Internationale de l'Eclairage (CIE). The colour values from the VNIR instruments were compared with reference values collected from three Minolta instruments designed specifically to measure colour. In general, there was excellent agreement between the VNIR and Minolta colour measurements. There was more variation among the readings from the VNIR instruments than among the readings from the Minolta instruments, probably due to slight differences in optics and geometry among the VNIR instruments. A major advantage of the VNIR colour measurements is that they are valid across a broad range of products, in contrast to most NIR equations which are product specific. Using VNIR instruments in this manner provides an efficient means of simultaneously providing chemical and colour quality information about many food and agricultural products. However, improved VNIR software is required to fully realize the potential of VNIR instruments to provide colour quality information to complement the traditional NIR chemical-based information. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.