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Evaluating the Use of Handheld near Infrared (NIR) Spectrometers in Food Adulteration Detection and Feed and Forage Analysis
Miniature near infrared (NIR) spectrometers have flooded the marketplace recently, but with lower grade optical components and microprocessors than benchtop spectrometers, these handheld devices need to be evaluated rigorously across a wide range of food matrices and potential applications. In this research, two handheld spectrometers were evaluated for accuracy at (1) detecting and quantifying metanil yellow (MY) in turmeric spice (2) predicting the composition of warm-season grasses, and (3) estimating crude protein content (CP) of mixed forage and feedstuffs. The ability to transfer calibration models from benchtop spectrometers to handheld devices was also investigated. The handheld devices evaluated were a transportable spectrometer (H1), capable of measuring absorption bands in the full NIR range (780-2500 nm), and a smartphone spectrometer (H2) capable of measuring absorption bands in the second and third overtone regions (900-1700 nm). These two instruments represent the low and high ends of commercially available handheld NIR devices in terms of size, technical specifications, and costs. Results from Case Study I showed that H1 could be used to classify MY-adulterated turmeric powder according to source of adulteration and to quantify MY levels up to 30% (w/w). A calibration model built for a benchtop spectrometer was also transferred to H1 with minimal loss in prediction performance. In Case Study 2, H1 and H2 could be used to screen warm-season grasses for nitrogen content (N) and in vitro dry matter digestibility (IVDMD), but not for estimating fiber components. Scanning samples through polypropylene (PP) film reduced accuracy of N predictions, but this could be overcome by excluding PP absorption bands in the calibration. A calibration model for N developed for a benchtop spectrometer was transferred successfully to H1 and H2 with minimal loss in prediction performance. Finally, in Case Study III, both H1 and H2 accurately predicted CP of mixed forage and feedstuffs, enabling their use at monitoring of feed CP at different stages of postharvest operations.
Rukundo, Isaac R, "Evaluating the Use of Handheld near Infrared (NIR) Spectrometers in Food Adulteration Detection and Feed and Forage Analysis" (2020). ETD collection for University of Nebraska-Lincoln. AAI28257289.