By Joseph Jensen – Ph. D. Candidate, Montana State University – Barley, Malt & Brewing Quality Lab
As the saying goes: Time is money!
The malting process is resource-intensive, requiring water and energy over a week for a single batch. If malt processing time could be shortened it could save maltsters money. One way we can do this is by looking at the speed of seed hydration. Malt times could be reduced by increasing the rate at which water enters the seed and wets the endosperm.
But is there a cost? Historically, faster hydrating lines lacked dormancy. Seeds with dormancy will not germinate until a certain amount of time has passed after seed maturation. The time can be from a few days to months, ensuring germination does not occur prior to or during harvest, preventing pre-harvest sprouting (PHS).
Growers cannot sell pre-harvested grain for malt because it has already germinated. Breeders have selected against dormancy because it was thought faster hydration only occurred in barley without dormancy. Therefore, most modern North American malt lines are susceptible to PHS.
Can we have our cake and eat it too?
We are searching for fast-hydrating lines with dormancy in a genetically diverse population of heirloom barley lines with origins from around the world, which was grown in Bozeman Montana in 2018 and 2019. Looking at this diverse panel allows us to find genes of interest that we might not normally find when looking at modern malting barley populations. With this population, we assessed malt quality, dormancy, and hydration index.
Dormancy and speed of hydration are traits any maltster can measure. To determine dormancy, we use germination protocols developed by the American Society of Brewing Chemists (ASBC). Testing began 24 days after harvest and each line was tested weekly to see when it would break dormancy. If a line had a germination rate of 95% or greater, it was considered to have broken dormancy and not tested again the next week.
The hydration index (speed of hydration) was calculated using the Chapon test. For this test, we assessed the hydration index at steep out by boiling a subsample of grain for one minute. Then 25 seeds from this subsample were cut in half and placed into one of four categories by rating the fraction of hydrated endosperm (see picture).
The categories were given points as follows:
- 0 to ¼ – 1 point
- ½ to ¾ – 2 points
- ¾ to 1 – 3 points
- Fully hydrated – 4 points
The points for each line are totaled and can fall between 25 and 100. Lines in this population varied between 26 and 78 points so none were completely unhydrated or completely hydrated at steep out. We also made malt and ran quality analysis on the population following ASBC protocols.
We performed a statistical analysis called association mapping to find genetic regions or quantitative trait loci (QTLs) that were responsible for our traits of interest. From this, we found 43 QTLs related to malt quality traits, 5 related to dormancy, and 6 related to the speed of hydration. Fortunately, several QTLs that increased the speed of hydration also improved malt quality. One of the hydration index QTLs showed a genetic region that would increase the speed of hydration and decreased beta-glucan levels, and another QTL showed increases in the speed of hydration, malt extract, and alpha-amylase while decreasing beta-glucan.
Importantly, none of the speed of hydration QTLs impact dormancy. Genetic control over dormancy is at least somewhat independent of the genetic control of the speed of hydration. Therefore, a line can be dormant, preventing PHS, and fast hydrating, saving time, money and improving quality.
We can have our cake and eat it too!