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M. Manley and P. J. Williams
products [5], beer [6], wine [7], fruit and vegetables [8] as well as sensory properties
of foods [9]. Commodities not considered in earlier years include cocoa beans [10],
pistachio nuts [11], hazelnut kernels [12] and honey [13]. Investigations on olive oil
[14] are still prominent.
Although NIR spectroscopy should theoretically only be applied to organic materials, of which the C–H, O–H and N–H bonds absorb in the NIR region, calibration
models can also be developed to predict physical properties of samples. Wheat and
maize kernel hardness are related to the particle size of the flour and meal, which can
be measured due to the different size particles scattering the NIR light differently.
It is also possible to measure the content of disolved salt (NaCl), which does not
absorb in the NIR region, in food products [15]. This is because the presence of salt
causes a shift in the water bands along the wavelength axis proportional to the salt
concentration. The magnitude of the shift depends on the salt concentration which
can be measured by NIR spectroscopy.
Food authenticity issues are a major concern in the industry and products or
ingredients that are high in value are usually targeted [16]. Products with Protected
Designation of Origin (PDO) or Protected Geographical Indication (PGI) which are
usually produced at high costs are also prone to be adulterated with cheaper substitutes. Due to the complexity of the food matrix and its heterogeneous composition,
it is difficult to identify adulterated products. The variability of the adulterations
adds to this complexity. Adulteration has also become more refined in recent years.
NIR spectroscopy has been evaluated for its potential to detect adulteration and/or
confirm the authenticity of food products for many years. Manley and Baeten [17]
recently provided an extensive review on the use of NIR spectroscopy in authenticity
studies. NIR spectroscopy adulteration studies are expensive to perform due to the
costs involved to collect suitable and large sample sets that include adequate variation. Because of this, many authenticity studies are performed on a limited number
of samples, thus usually only demonstrating feasibility. There is a good likelihood
of successful applications in industry, but such work is usually performed in-house
and the results are not made available in the public domain.
In this chapter, quantitative and qualitative NIR spectroscopy food and beverage
applications will be considered and briefly discussed.
15.2 Cereals and Cereal Products
The first application of NIR spectroscopy in the wheat industry dates back to 1975
when NIR spectroscopy was used to predict protein content in wheat [3]. Protein
and moisture content measurements on wheat flour and whole grain are still one of
the most widely used applications. Routine wheat applications have since extended
to also include wheat hardness as well as ash content and starch damage. NIR spectroscopy is now commonly used as a rapid cereal quality control technique, and
factory calibrations for a number of the measurements are readily available which
can be purchased from NIR instrument manufacturers.
M. Manley and P. J. Williams
products [5], beer [6], wine [7], fruit and vegetables [8] as well as sensory properties
of foods [9]. Commodities not considered in earlier years include cocoa beans [10],
pistachio nuts [11], hazelnut kernels [12] and honey [13]. Investigations on olive oil
[14] are still prominent.
Although NIR spectroscopy should theoretically only be applied to organic materials, of which the C–H, O–H and N–H bonds absorb in the NIR region, calibration
models can also be developed to predict physical properties of samples. Wheat and
maize kernel hardness are related to the particle size of the flour and meal, which can
be measured due to the different size particles scattering the NIR light differently.
It is also possible to measure the content of disolved salt (NaCl), which does not
absorb in the NIR region, in food products [15]. This is because the presence of salt
causes a shift in the water bands along the wavelength axis proportional to the salt
concentration. The magnitude of the shift depends on the salt concentration which
can be measured by NIR spectroscopy.
Food authenticity issues are a major concern in the industry and products or
ingredients that are high in value are usually targeted [16]. Products with Protected
Designation of Origin (PDO) or Protected Geographical Indication (PGI) which are
usually produced at high costs are also prone to be adulterated with cheaper substitutes. Due to the complexity of the food matrix and its heterogeneous composition,
it is difficult to identify adulterated products. The variability of the adulterations
adds to this complexity. Adulteration has also become more refined in recent years.
NIR spectroscopy has been evaluated for its potential to detect adulteration and/or
confirm the authenticity of food products for many years. Manley and Baeten [17]
recently provided an extensive review on the use of NIR spectroscopy in authenticity
studies. NIR spectroscopy adulteration studies are expensive to perform due to the
costs involved to collect suitable and large sample sets that include adequate variation. Because of this, many authenticity studies are performed on a limited number
of samples, thus usually only demonstrating feasibility. There is a good likelihood
of successful applications in industry, but such work is usually performed in-house
and the results are not made available in the public domain.
In this chapter, quantitative and qualitative NIR spectroscopy food and beverage
applications will be considered and briefly discussed.
15.2 Cereals and Cereal Products
The first application of NIR spectroscopy in the wheat industry dates back to 1975
when NIR spectroscopy was used to predict protein content in wheat [3]. Protein
and moisture content measurements on wheat flour and whole grain are still one of
the most widely used applications. Routine wheat applications have since extended
to also include wheat hardness as well as ash content and starch damage. NIR spectroscopy is now commonly used as a rapid cereal quality control technique, and
factory calibrations for a number of the measurements are readily available which
can be purchased from NIR instrument manufacturers.