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How to Obtain a Reliable and Quick Assessment of Alveographic Values

22/01/2019 10:51

How to Obtain a Reliable and Quick Assessment of Alveographic Values

World production of wheat totals 700 million tons annually, making it one of the main food staples of our diet.   Different varieties, agricultural practices and climatic conditions yield widely varying results with respect to quality. 

One of the most common quality indicators used is protein content, but it is not the only parameter that should be considered, other analyses are required to determine the overall quality of wheat.  Many standardized methods exist on the market today, the Alveograph is one of these methods.

The wheat must be conditioned and milled before the Alveograph test is performed on flour samples.  This analysis process requires a total of 29 hours, an amount of time that is not compatible the efficient receipt of wheat during the harvesting period.

Therefore, alternative methods have been developed to enable the upstream cereal industry (grain collection cooperatives and organizations) to use wheat quality indicators such as Alveograph values.  These methods need to be very quick and simple to use, while providing sufficiently reliable data that can be trusted.  Attempts were made using near infrared devices but the results proved to be unsatisfactory.

 To this end, in 2014, CHOPIN Technologies, in partnership with our Turkish distributor ABP and the Alaybeyi GIDA Company, which is based in Konya, initiated a program to develop an alternative method for predicting Alveograph values. 

 We came up with a technical solution consisting of an 8 minute rheological test, performed using the Mixolab 2.  The protocol is called WiXO. WiXO is conducted directly on ground wheat, at constant hydration, making it possible for this alternative method to be performed very quickly.  In fact, the entire process, from delivery of the sample to the final results (grinding, measurement of the moisture content, weighing, WiXO analysis), takes less than 15 minutes!

Figure 1 shows a typical curve obtained by testing a ground wheat sample using the WiXO protocol.  Two distinct phases are indicated:  the first 4 minutes of kneading at a speed of 80 rpm to develop the dough, then the last 4 minutes at an increased speed of 240 rpm in order to test the strength of the gluten network. 

How to Correlate the WiXO Curve with the Alveograph Results

More than 350 wheat samples produced over 3 harvest years were analyzed using the Alveograph reference method (ISO 27971-2015) along with the WiXO protocol.  The database generated was analyzed using the MiniTab® statistical tool. Predictive models of the Alveograph results were developed in this way. 

Figure 2 shows the results obtained by comparing the parameter W (baking strength) from the WiXO analysis with the W value measured using ISO 27971-2015.  For the 307 samples used during the development stage, the range was [36-545], the correlation coefficient (r²) was 0.74 and the average difference compared to the reference was 36 points.  For the 52 validation samples, the range was [64-501], the correlation coefficient (r²) was 0.77 and the average difference compared to the reference was 39 points.

The results show that 2/3 of the samples were predicted within the control limits, which is an excellent performance result for an alternative method.

Not only the W value!  P, L and I.e. parameters are also available!

The W value can be identical for Alveographic profiles of very different qualities of flour.  Therefore, it is important to not just consider the W value, but to also include at least one other parameter.

Recent work has focused on the parameters of tenacity (P), extensibility (L) and the elasticity index (I.e).

In 139 samples, covering a wide range of flours, 50%, 70% and 80% of the samples were found to be within the reference control limits for the parameters of tenacity, extensibility and the elasticity index respectively.

These predictive models are included in the latest Mixolab 2 software and are therefore available to all current and future Mixolab 2 users.

For more information, contact us at info@chopin.fr

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