Jb. Reeves et Cm. Zapf, Spectral library searching: Mid-infrared versus near-infrared spectra for classification of powdered food ingredient, APPL SPECTR, 53(7), 1999, pp. 836-844
The objective of this study was to determine the potential of using mid- or
near-infrared diffuse reflectance spectra to construct food ingredient spe
ctral libraries for product identification and checking. Samples (106) cons
isting of buttermilk, dehydrated onion, cheese and milk-egg powders, wheat
hours, and two powdered seasonings were scanned "as is" (not diluted with K
Br using diffuse reflectance) at 4 and 16 cm(-1) resolution in the mid-infr
ared on a Digilab FTS-60 and a Perkin-Elmer Model 2000 and in the near-infr
ared on an FTS-60 (4 and 16 cm(-1) resolution) and NIRSystems Model 6500 sc
anning monochromator (10 nm bandwidth). A custom-made sample transport devi
ce was used on the FTS-60, a rotating sample cup on the NIRSystems 6500, an
d a stationary cell for the Perkin-Elmer 2000. Every third sample of each g
roup was used as a test sample and searched against a library containing th
e remaining samples. Results showed that only full spectrum based searches
with the use of Euclidian distance or correlation (with or without a first
derivative) were useful. All unknowns were correctly classified by using ne
ar-infrared spectra generated on either the scanning monochromator or the F
TS-60 (4 cm(-1) resolution) or by using any of the mid-infrared spectra. Re
sults demonstrated that near- or mid-infrared spectral libraries of powdere
d food ingredients can be used for product identification and checking.