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FT-NIR for Targeted and Non-Targeted Adulteration Screening

Trying to maintain brand reputation and product quality has led to increased focus on qualifying raw materials and ingredients used in food production. In addition to traditional quality parameters like moisture, fat, and protein, detection of adulterants plays a critical role to ensure food safety and quality.

The USP (US Pharmacopeial Convention) Food Fraud Database currently lists hundreds of incidents of economically motivated adulteration (EMA), substitution, counterfeiting or mislabeling of food products. These include olive oil and milk powder and some prominent adulterants e.g. melamine.

FT-NIR is a valuable tool for screening raw materials with an excellent cost-benefit ratio and unrivaled ease-of-use. The high information content of NIR spectra provides a finger print of the complete sample. The the spectra of the incoming raw materials are compared with those measured using samples of known quality. This allows a non-targeted screening of adulterants or contaminants within the  detection limits. If a material is tested positive on adulteration, further investigations with complementary analytical methods can be carried out to determine the exact identity of the adulterant.

Bruker FT-NIR spectrometers offer a fast and effective tool for quality control of raw materials,  intermediate products and final products. As a non-destructive method without any sample preparation it is already extensively used in the food industry for analyzing main constituents such as protein, moisture, fat, lactose, ash, and fiber.

With the measurement of a single spectrum the sample can be evaluated in a three-step process:


1. Identification

The first step analyzes if the spectrum of an incoming raw material fits to the statistical population of authentic and previously accepted batches. This way it can be checked if the correct raw material was delivered and properly labeled to avoid usage of the wrong ingredient in production.


2. Conformity

In this step the sample is further qualified using conformity test, which is a more specific evaluation of the spectrum. Checking for conformity with an individual threshold at each data point allows a real fingerprinting of the material with adjustable sensitivity.


3. Quantification

Finally, during the quantification of the different constituents, an outlier test based on the Mahalanobis Distance is performed. Again the analysis spectrum is compared to the sample population in the individual quantification models.

Bruker Optics comprehensive spectroscopy software OPUS provides powerful tools for identification, qualification by conformity test and quantification of raw materials and finished products. The powerful MultiEvaluation package combines these individual evaluation tools to a single routine with hierarchical evaluation.

The software user interface links measurement and evaluation methods to a single raw material or product. The operator only needs to select the product to be analyzed and the correct measurement and evaluation methods are performed automatically.

Ident 3D Score Plot 2
3D scores plots showing different material groups in an identification library
Display of reference spectra in a conformity test method (green) with spectra detected as outliers (blue)
TANGO Display
Result screen for a quantification showing a Mahalanobis outlier for the fat evaluation