Non-Contact Transflectance near Infrared Imaging for Representative on-Line Sampling of Dried Salted Coalfish (Bacalao)

Abstract

This paper describes a multi-spectral imaging near infrared (NIR) transfl ectance system developed for on-line determination of crude chemical composition of highly heterogeneous foods and other bio-materials. The system was evaluated for moisture determination in 70 dried salted coalfi sh (bacalao), an extremely heterogeneous product. A spectral image cube was obtained for each fi sh and different sub-sampling approaches for spectral extraction and partial least squares calibration were evaluated. The best prediction models obtained correlation R 2 values around 0.92 and root mean square error of cross-validation of 0.70%, which is much more accurate than today's traditional manual grading. The combination of non-contact NIR transfl ectance measurements with spectral imaging allows rather deep penetrating optical sampling as well as large fl exibility in spatial sampling patterns and calibration approaches. The technique works well for moisture determination in heterogeneous foods and should, in principle, work for other NIR absorbing compounds such as fat and protein. A part of this study compares the principles of refl ectance, contact transfl ectance and non-contact transfl ectance with regard to water determination in a set of 20 well-defi ned dried salted cod samples. Transfl ectance and non-contact transfl ectance performed equally well and were superior to refl ectance measurements, since the measured light penetrated deeper into the sample.

On-line and non-destructive measurement of core temperature in heat treated fish cakes by NIR hyperspectral imaging

“…It has been described in detail in several scientific articles concerning on-line quality determination of foods (Wold et al, 2006;ElMasry & Wold, 2008;Wold, Kermit, & Woll, 2010). The scanner was installed above a conveyor belt suitable for foods.…”

“…Applications of NIR imaging are already established in the food processing industry for e.g. quality grading of crabs, salmon fillets and pork meat (Wold et al, 2006;Segtnan, Høy, Lundby, Narum, & Wold, 2009;O'Farrell et al, 2010), and the opportunities are versatile. It is well known that the near-infrared spectrum of water is affected by sample temperature (Buning-Pfaue, 2007).…”

Near infrared spectroscopy for on/in-line monitoring of quality in foods and beverages: A review

“…A muli-spectral imaging NIR transflectance system was developed for on-line determination of moisture content in dried salted coafish (bacalao) (Wold et al, 2006). The combination of NIR transflectance measurement with spectral imaging allows rather deep penetrating optical sampling and large flexibility in spatial sampling patterns and calibration approaches.…”

Automatic freshness assessment of cod (Gadus morhua) fillets by Vis/Nir spectroscopy

“…The spectrometer has a focal distance of 1000 mm and depth of field of 25 mm, and was positioned 1030 mm above the conveyer to ensure good focus on both the thin belly flap and the thick loin part of the fillet. Using a fiber optic light line on both side of the imaging area, instead of one (Sivertsen et al, 2009;Wold et al, 2006), increases the light intensity on the fillet and eliminate the problem of not having a signal in the neck or tail region of the fillet. Each fiber optic light line is 200 mm long and powered by three 150 W (21VDC) aluminum coated halogen lamps.…”