In-depth flour analysis with near-infrared spectroscopy

Janel Kane explores flour identification modelling using near-infrared spectroscopy

Absorption measurements can be used to determine the properties of various samples, such as concentrations of chemicals and the quality of plastics. Not only can absorption spectra be used to identify the characteristics of many types of samples, they can also be used to characterise the unique spectra of each sample to generate a chemometric model. Near-infrared (NIR) spectroscopy is leading the way for the future of agriculture and food production for both qualitative and quantitative measurements. The same goes for reflection measurements. Reflection spectra can characterise the unique properties of various samples, such as grains, fruits and plastics.

Description of the near-infrared spectroscopy system

A halogen light source is ideal for absorption and reflection measurements because of its power and good output in the NIR range, which is the wavelength range many researchers use to characterise consumables, such as grains and food products. This aids in revealing properties not observable with the naked eye. The halogen light source used in this testing is the AvaLight-Hal-S-Mini. From visible light to near-infrared, that’s where the AvaLight-Hal-S-Mini works best. It’s a compact, stabilised halogen light source, with adjustable focusing of the fibre connection, maximising output power at the desired wavelength. The light source also has an adjustable output power to provide extra power or longer bulb life. The light source is connected via SMA termination directly to the illumination leg of a reflection probe.

The reflection probe is fixed on our reflection stage to illuminate and measure the samples. The spectrometer leg of the reflection probe is connected via SMA termination to the AvaSpec-NIR256-1.7-EVO.

Measuring in the near-infrared range

For measurements in the near-infrared range up to 1.7 µm, Avantes offers a new series of uncooled spectrometer configurations. Both instruments deliver the same advanced performance specifications, such as a sample speed of only 0.53ms/scan and integration times as fast as 10 µs. For applications where resolution is key, or more data points for modelling are required, the 512-pixel detector is an ideal choice. The AvaSpec-NIR256/512-1.7-Evo spectrometers pair the same InGaAs array detectors with the firm’s ultra-low-noise electronics board featuring USB3 and Giga-Ethernet connection port. Digital and analogue I/O ports enable external triggering and control over the shutter and pulsed light sources and choose from two distinct software-controlled gain-setting modes, high-sensitivity mode (HS, default) and the low-noise mode (LN). The unit used in this testing is configured with a slit-50 and OSF-850.

Near-infrared spectroscopy methodology description

For this experiment, the absorbance and reflection modes in the AvaSoft software were used. These modes are built to capture the absorbance of samples in absorbance units and the reflectance of samples in percent, respectfully.

The set-up was used to measure the absorbance and reflection spectrum of four different types of flour: white flour, wheat flour, almond flour and tapioca flour. Both the white and wheat flour types contain gluten, while the almond and tapioca flours are gluten-free. A WS-2 reflection tile will be used as the reference. This tile will be used to optimise the integration time and averaging for the spectrometer.

NIR spectroscopy analysis

Although each flour sample appears similar to one another at an initial look at the spectra, such as sharing similar peaks and valleys, it is visible that each sample has its own unique spectral fingerprint. Upon scaling the y-axis, it is clearly visible that each type of flour has a unique spectrum. The white flour and wheat flour samples both contain gluten, while the almond flour and tapioca flour are gluten free. For the next steps, it can be possible to put together a chemometric model for identifying gluten levels in the flours of baked goods and characterise the traits. Avantes frequently works with LabCognition and its software, Panorama, for these types of applications.

Flour analysis test conclusion

In conclusion, NIR spectroscopy provides a reliable and effective way of measuring many types of food samples and their ingredients. The accuracy of Avantes NirLine spectrometers is a strong advantage in developing reliable chemometric models and for collecting reliable data. Additionally, the fit for use of these instruments in process control environments is evident from the 10ms integration time sample rate on diffuse flour samples. The instruments also facilitate process control through the industrial communication protocols (Ethernet), onboard data processing capabilities and digital/analogue I/O. Combined with the powerful capabilities of Panorama or other multivariate data modelling tools, a highly accurate model capable of predicting the levels of gluten in baked goods can be developed. To further improve this model, additional samples can be added to the calibration.

Janel Kane is with Avantes

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