Understanding and addressing concerns from Japanese customers about changes in the gluten properties of CWRS wheat exposed to heat stress

Dough qualities of CWRS wheat exposed to heat stress

We recently started a collaboration with the milling and baking industry in Japan, which is the largest customer of No. 1 Canada Western Red Spring (CWRS) wheat. This was done to address concerns that Japanese bakers had about the long mixing requirements and low extensibility of dough made from CWRS wheat grown in the hot and dry years of 2021 and 2023. They described the dough as “strong but brittle and inextensible” and reported that their processes had to be adjusted. This resulted in increased production costs and an undesirable variation in end product quality.

We compared the results of our Extensograph and Farinograph tests from 2020 to 2023 and confirmed that doughs made from CWRS wheat exposed to heat stress were significantly stronger, as indicated by higher maximum resistance (R_max) values, and longer development and stability times (Table 1). The extensibility of dough was similar, however, for all four years. Our standard test methods, widely used internationally, did not capture the brittle and inextensible dough properties described by Japanese customers.

Does gluten protein composition change under heat stress?

To better understand the effect of heat stress on dough, we fractionated the gluten proteins in flour samples of CWRS wheat from 2020 to 2023 into insoluble glutenin, soluble glutenin and monomeric proteins. Insoluble glutenin contributes to dough strength and the latter two fractions contribute to the extensibility of dough. The results show a higher ratio of insoluble glutenin to soluble glutenin in wheat exposed to heat stress (Figure 1), which is consistent with a stronger dough and longer mixing time. However, the brittle and inextensible dough properties are not well explained by the distribution of gluten protein fractions.

Assessment of commercial flour samples from Japan

We then assessed six commercial flour samples, milled mostly from CWRS wheat, that were provided by a major wheat milling company in Japan. Our collaborator reported that the dough properties of the samples ranged from well balanced to brittle and inextensible. We found no significant differences in extensibility between the six samples, however, using our standard test methods (Table 2).

Technical exchange with Japan

An in-person technical exchange was arranged with Japanese experts who have extensive experience in assessing dough handling properties. Our Sponge and Dough bake method was compared with the Shokupan bake method used in Japan and some notable differences in formulation and methodology were observed. With input from the Japanese experts, the Shokupan bake method was adapted for use with our equipment and our staff were trained in the subjective scoring system used in Japan to assess dough qualities. For example, extensibility is evaluated by how far the dough stretches before tearing and thinly stretched dough is considered brittle if it breaks easily when lightly touched. In a blind re-test of the Japanese commercial flour samples using the Shokupan bake method, our staff were able to differentiate the dough properties important to the Japanese baking industry (Figure 2).

We also evaluated the Shokupan dough properties of the 2023 CWRS wheat samples received by the Harvest Sample Program and the results were consistent with the description of dough made from 2023 wheat cargos received by Japan.