Alveograph – Sources of Problems in Curve Interpretation with Hard Common Wheat Flour

Nancy Edwards and Jim Dexter

The alveograph was introduced in France by Chopin in the 1920s, and has been used extensively in Europe, South America and the Middle East for testing of flour quality since that time. It was initially developed to provide information on the baking quality of European bread wheats which are comparatively softer, weaker, and lower protein than North American hard red spring and hard white spring wheat.

A large part of the problem in assessing the quality of hard red spring and hard white spring wheat with the alveograph is related to starch damage and the water absorbing capacity of the flours produced from these wheats. The AACCI (Approved Method 54-30A) and ICC (Method 121) standard methods for alveograph both call for testing at fixed water absorption of 50% (15% mb). Under similar milling conditions hard red spring and hard white spring wheat will produce flour that is higher in starch damage than softer wheat, resulting in significantly increased water absorbing capacity. In addition varying milling conditions, particularly reduction grinding settings, results in variable flour water absorption for a given hard wheat.

Regardless of milling conditions, dough prepared at 50% absorption from hard common wheat flour is significantly under-hydrated and therefore is stiff and inextensible. As an example, Figure 1 shows alveograph curves for a Wheat, No. 1 CWRS 13.5 flour tested at 50% absorption (curve A), 60% absorption (curve B) and at its farinograph absorption of 66.7% (curve C). There are significant differences among the curves for the same flour prepared at different absorptions. At farinograph absorption the alveograph curves exhibits considerably more extensible dough with much less resistance to deformation.

Figure 1. Alveograph curves for No. 1 CWRS 13.5 flour. A dough prepared at 50% absorption; B dough prepared at 60% absorption; C dough prepared at farinograph optimum absorption of 66.7%.

Increasing starch damage results in reduced dough extensibility (L) and increased pressure (P). As an example see Figure 2, where a single CWRS wheat sample was divided and milled in different ways to produce a flour with high starch damage (45 Farrand units, 68.0% farinograph absorption) and a flour with low starch damage (9 Farrand units, 59.6% farinograph absorption). It becomes obvious that by increasing the proportion of high starch damage flour in a blend with low starch damage flour there is a linear increase in P, and a linear decrease in L with increasing proportion of high starch damage flour.

The impact of flour water absorption on alveograph properties is now so well established that Chopin is marketing the Alveo-Consistograph. The Alveo-Consistograph determines the water absorption required to meet a specific dough consistency. This constant consistency dough is then used to perform the alveograph test, thus overcoming the problems associated with dough hydration.

Figure 2. Alveograph curves of Benito red spring wheat milled to high and low starch damage.  The highest starch damage flour had farinograph absorption of 68.0% while the lowest starch damage flour had farinograph absorption of 59.6%.  Curves from highest “P” to lowest “P” values represent blend of high to low starch damage flours mixed at ratios of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100.  These results have been published in the Canadian Institute Food Science and Technology Journal, Volume 20, pages 75-80, 1987.  A copy can be obtained from the CGC library by emailing library@grainscanada.gc.ca.