Attributes between a drought year and non-drought year are mixed.
My previous article in the Second Quarter issue of Milling Journal compared the effects of drought on hard red winter (HRW) wheat by comparing a severe drought year (2023) to non-drought year (2019). Analysis of the data suggests wheat crop differences between two regions, Gulf and Pacific Northwest, given the assumed drought conditions.
Considering those differences were observed with limited variable definition concerning drought (severity and timing), further exploration of individual wheat data combined with appropriately refined location, weather, planting, and timing information is warranted.
As such, improved environmental monitoring is needed to properly understand drought stress impacts beyond production alone. This article focuses on the effects of drought on Kansas HRW wheat comparing a drought year (2023) and a non-drought year 2019).
Factors Impacting Wheat Production and Milling and Baking Quality
In this analysis, the varieties, agronomic conditions, and practices are more similar than would be observed across the entire U.S. HRW wheat production area analyzed in the previous article. The production and utilization of wheat in milling and baking is complex. Figure 1 below presents a simplified relationship between wheat variety, environment, and their anticipated connection between milling and baking quality. There are more variables than those identified in the figure, and it should not be difficult to imagine that for each variable there are numerous alternative levels or values. The combinations are mind-boggling.
The Kansas Farm Bureau reports there are 30,000 varieties covering the six major classes of wheat in the United States. Imagine, then, the range of variables such as soil type, rain fall, temperature, and fertilization practices, as well as timing- and duration-specific variables.
Differences in wheat varieties grown in any area of the country vary from year to year. In some instances, the wheat planted may be certified seed, while in others, it may be cleaned wheat from the previous harvest being used as seed wheat for the next year. It is understood that utilizing previously harvested wheat as seed stock for multiple years may have a negative impact on expression of the desired traits of the original certified seed stock. Variety preferences are sometimes identified by a mill securing wheat from a known draw area to reduce variability and to maintain flour quality.
The variety analysis identifies approximately 30-42% of total Kansas wheat production. Between 2019 and 2023, the number of varieties identified increased from 20 to 22. In 2023, 12 varieties were added to the list, while 10 varieties shown in 2019 were removed from the variety list. Wheat varieties in Kansas are ever changing to meet agronomic challenges. It is important for the miller to maintain an awareness of variety development and releases in the mill’s draw area and beyond, as production and quality issues may force selecting wheat from outside the typical draw area.
Table 1 presents Kansas wheat crop properties in 2023 (drought) and in 2019 (non-drought). During the drought year, the number of high-protein samples was much greater than in the non-drought year. The overall crop protein content in 2023 was also higher than in the non-drought year 2019. Kernel size is greater in the non-drought year than observed in 2023. Within either year, higher-protein wheat provided harder kernels and increased flour yield. In both 2019 and 2023, the low-protein wheat category was less than 11.5%, medium-protein category was between 11.5% and 12.5%, while the high-protein category was greater than 12.5% all on a 12% moisture basis. The average protein content of low-, medium-, and high-protein categories was increased because of drought conditions.
Table 2 provides the average milling results for each of the protein categories in 2023 and 2019. The higher protein and harder kernel of the drought-impacted wheat from 2023 gives the impression that flour production moved further down the reduction system. It is not known if this was the result of harder endosperm, larger particle size released into the reduction system, or a difference in sifting properties.
The non-drought impacted wheat of 2019 resulted in an increase in break flour production, as well as sizings flour production over that of the drought-impacted 2023 wheat. The increase in break flour production may be the result of increased kernel size observed or lower protein and softer wheat of the 2019 crop.
Impact to the Milling Process
Changes in wheat variety and growing conditions impact the location of flour production in the mill. To the extent these changes are problematic for the miller depends on how closely the mill and its individual systems are running to design capacity limits.
Keep in mind, a change in load of several percentage points basis the total mill may be a significantly larger increase for an individual milling system. These load changes may impact grinding, sifting, and purification as well conveying capacity.
Just as significant as load changes are material properties including bulk density, shape and flow properties which impact conveying and delivery of stock into various mill processes. Unfortunately, a single yield value from a laboratory mill does not convey all these observable changes, which ultimately impact commercial operation where design capacity is limited and system installation perhaps is compromised. It is well known to commercial millers that a new wheat crop or alternative wheat source can wreak havoc on an otherwise smooth-running operation. Millers are forced to respond and solve such processing problems daily.
Table 3 shows Kansas flour results for 2023 and 2019. As expected, the protein results follow the wheat kernel protein. Flour ash appears to be higher in the drought year, 2023, than in the non-drought year, 2019. Perhaps the bran was somewhat more brittle and shattered more easily; however, this suggestion is speculative at best. Starch damage appears to be greater in the non-drought year and may be related to flour production in earlier stages of the milling process. Flour color measurements appear to be comparable between the two years.
Tables 4 and 5 provide physical dough test results for 2023 (drought) and 2019 (non-drought) years. Farinograph and extensograph results are shared in Table 4, while alveograph and mixograph results are provided in Table 5. Generally, these data follow protein content characteristics. Take care to look at the average, minimum, and maximum values observed for the various measures. It is important to note that in many cases, the range of test value results for an attribute in each protein category often overlaps.
Are the differences observed a result of wheat varieties within the sample or test method variation? Most likely, it is a combination of both, indicating how much of a challenge it is to achieve adherence to tight specifications that do not accommodate the random nature of wheat. Alternatively, it suggests the need to control the wheat selection process to achieve compliance to tight flour specifications. Recall, previous comments on variety changes between 2023 and 2019; even wheat sourced from the same draw area changes from year-to-year due in part to factors not limited to those shown in Figure 1.
Baking Results
Of course, the final test of wheat quality is its performance in making its intended finished product, in this case bread. Baking results comparing the performance of 2023 (drought) and 2019 (non-drought) years are provided in Table 6. The increase in protein content observed in the drought year appears to have increased mixing time, baking water absorption, and loaf volume. On overall average, the baking characteristics remained similar.
Conclusion
Drought appears to have contributed to increased wheat protein in 2023 compared to 2019, a non-drought year. There appears to be somewhat of a shift in the location of flour production within the laboratory mill between the two years. Flour from the two different years appears to have provide acceptable level of performance.
So, what did we learn really? Wheat sourcing for flour production to meet bakery specifications is complex. Scientific studies with controlled parameters often lead us to believe factors such as protein quantity or quality can be strongly related to flour absorption or loaf volume with a high level of correlation. Often, that high level of correlation is reduced or compromised by the reality inherent to wheat production. Perhaps we can explore such an example in the next article.
Dr. Jeff Gwirtz is CEO of JAG Services, Inc., an international consulting company in Lawrence, KS; 785-341-2371; jeff@jagsi.com. He also is adjunct professor in the Department of Grain Science and Industry at Kansas State University, Manhattan.
From the 3rd Quarter 2024 Milling Journal