September 12, 2017

13/09/2017: Measuring protein quality using infrared

by Dr Antony Hartell, NIR Product Manager, Rapid Analysis

Protein quality is an important parameter for the assessment of milling wheat

The ability of dough to maintain its shape during the baking process is critical and depends on gluten strength, which in turn relates to protein quality. Protein quality falls with wheat milled from grains of lower specific weights. 

Image credit: Buchi
Unfortunately, this is difficult to pick up with routine testing, as even when protein quality falls the overall apparent protein level can appear near constant. This is a consequence of a larger contribution from bran protein, which could go undetected when measurements of protein content only are relied upon.

At grain intake, most flourmills typically use near infrared spectroscopy (NIR) and other laboratory techniques to inspect grain and measure parameters such as protein level, moisture, specific weight, and Hagberg Falling number.

Unfortunately, no rapid analysis technique exists to measure protein quality. The only way to assess this parameter is to mill the grain and then use the flour to produce test bakes. This is a time consuming activity.

NIR is a well-established rapid analytical technique used to assess wheat quality since the 1970s. Millions of samples each year are analysed by NIR with many different instruments available to those involved in the milling and grain industries. NIR is attractive due to the ease of use and lack of sample preparation.

No chemicals are required and modern spectrometers come supplied with ready-to-use calibrations that only require minimal set up times. Basic NIR instruments provide acceptable predictions for protein and moisture content only.

At the opposite end of the scale, advanced NIR systems are able to predict not only compositional parameters but also can predict rheological parameters and use advance statistical methods to classify wheat and flour by type.

Hardware has been developed that has taken NIR out of the lab and placed it firmly at the production line; either as a robust version of the lab instrument (e.g. BUCHI NIRMaster) or mounted directly to the production line as with BUCHI NIR-Online range of sensors and accessories.

BUCHI Labortechnik AG supply ready-to-use NIR packages designed around the specific needs of the milling and bakery industry. The packages contain all of the hardware, software, calibrations and support packages needed to get started with NIR.

Users are able to tailor the software to meet their specific needs as the software has an open structure. As the end-user confidence increases, they are able also able to manipulate data and calibrations increasing the versatility of the instrument.

In addition, data entry and sample acquisition screens can be customised. Well-developed pre-determined calibrations are available to select, not only traditional chemical parameters such as moisture, protein and ash but also farinographic and alveographic rheological parameters including, for example, baking absorption, extensibility and starch damage.

Increasing demands are placed on the hardware as the complexity of the NIR prediction increases. In particular, the ability to acquire accurate spectra with high levels of repeatability that completely cover the full NIR spectral range is a key requirement when predicting rheological parameters.

Additionally, the instrument must not be sensitive to environmental changes such as temperature and humidity otherwise measurements can appear to drift. Modern spectrometers are much more robust than those of old and operate well in many different environments.

Visit the BUCHI website, HERE.

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine Milling and Grain
which is published by Perendale Publishers Limited.

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