Beer brewing secrets exposed
Cross section of mature barley grain: cube-shapes cells - aleurones - are located between the outer husk (red) and inner starchy endosperm. [University of Adelaide]
Australia-based researchers have revealed stunning fluorescence microscopy images of barley tissue, after discovering a link between the one of the grain's key enzymes and a specific tissue layer.
The latest discovery sheds light on the malting process and paves the way to more stable brewing methods and new malts for craft brewers.
The most important malting enzymes come from a layer of tissue in the barley grain called the aleurone, a health-promoting tissue full of minerals, antioxidants and dietary fibre.
Professor Matthew Tucker from the University of Adelaide School of Agriculture, Food and Wine, and colleagues, have now shown that the more aleurone present in the barley grain, the more enzyme activity the grain produced.
"Barley grains possess impressive features that make them ideal for creating the malt required by the brewing industry," says Tucker. "During the malting process, complex sugars within the barley grain are broken down by enzymes to produce free sugars, which are then used by yeast for fermentation."
"The levels of these enzymes, how they function and where they are synthesised within the barley grain are therefore of significant interest for the brewing industry," he adds. "Until now, it was not known that this key ingredient in the beer brewing process was influenced by the amount of aleurone within the grain, or that the aleurone was potentially a storage site for the enzyme."
The researchers used fluorescence microscopy to examine the aleurone in a range of barley cultivars used by growers and breeding programs in Australia, identifying remarkable variation in the aleurone layer between varieties.
Representation of the transverse sectioning process used to image barley aleurone tissue by fluorescence microscopy. (A) Schematic representation of barley grain sectioning prior to microscopy. The different tissue layers are indicated. (B to D) Wholegrain transverse sections viewed at 1× magnification using Zeiss Filter sets 46 (false-coloured red) and 49 (DAPI; false-coloured yellow) (E to J) Magnified views of the aleurone layers at 20× magnification, scale bar = 50 µm. Genotype names are indicated in each panel. [Learn more at Nature Scientific Reports]
Investigations revealed that barley grains possessing more aleurone had noticeably more activity in one of the key enzymes that breaks down starch and determines malt quality of barley, an enzyme called free beta-amylase.
"The results reveal a link between molecular pathways influencing early aleurone development and increased levels of free β-amylase enzyme, potentially highlighting the aleurone as a repository of free β-amylase at grain maturity," says Tucker.
"We think our findings show that it might be possible for breeders and geneticists to make use of this natural variation to select for barley varieties with different amounts of aleurone and hence different malting characteristics," he adds. "This will be of potential interest to large brewers who depend on stable and predictable production of malt, and also the craft brewers that seek different malts to produce beer with varying characteristics."
The researchers are now trying to find the genes that explain this natural variation.
Research is published in Nature Scientific Reports.