Application of Traditional Methods of Analysis and Modern Proteomics to Evaluate the Malting and Brewing Potential of the Novel Grain Kernza (Thinopyrum intermedium)

As the environmental impacts of beer is of increasing concern to maltsters, brewers and consumers, perennial cereal crops offer a more sustainable solution. Their extended lifespans have been shown to result in reduced water use, decreased added nutrient requirements, and lower overall environmental cost when compared to traditional annual cereals like barley and wheat. One new species of interest to the brewing industry is intermediate wheatgrass (Thinopyrum intermedium var. intermedium), developed by The Land Institute, in Salina, Kansas, USA, which has been recently released under the branded name Kernza®. By malting and later mashing this grain under varied conditions, the usefulness of this novel species in brewing was compared against barley (Hordeum vulgare L.), the global industry benchmark for malt. Here, the malted Kernza showed a significant increase in the amount of available fermentable sugars (extract) and free amino nitrogen (FAN) after mashing when compared to the raw Kernza grain. Furthermore, the Kernza malts produced wort that conformed to industry standards for low concentrations of β-glucan, and enough extract and FAN to support healthy fermentation. Extract and FAN in the Kernza malts were lower than in the barley reference, however, and the Kernza worts exhibited higher levels of undesirable soluble protein and haze. Kernza malts were also shown to perform better under multi-temperature step mash conditions than in an isothermal 65 °C infusion mash, comparable to the barley malt reference. In addition to industry standard methods applied to analyze the grains, malt, and wort here, modern mass-spectrometry-based proteomics methods were utilized to evaluate the changes to the protein makeup of these grains during different stages of the malting and brewing process. In the finished Kernza malt, several important proteins for brewing were identified, including mash-active enzymes such as α- and β-amylases, carboxypeptidase, and foam-positive proteins such as serine proteinase inhibitors (serpins) and lipid transfer proteins (LTPs). Furthermore, structural prolamin-type proteins, including multiple forms of gliadin and glutenin, were identified in the Kernza grains prior to malting, and which reduced in abundance during malting at rates similar to the hordeins in the barley reference, indicating that these malts were modified to degrees similar to commercial malts. Many of these proteins were also found in worts produced under different mash conditions, and their abundances followed similar trajectories to those produced with the barley malt. Additionally, for both Kernza and barley, multi-rest step mashes retained many important enzymes in the wort longer than the higher temperature infusion mashes. These analyses show that not only is Kernza a strong candidate to replace 100 % of the barley malt in the grist, but our insights into the Kernza proteome provide an indication for future breeding of this grain to encourage its wider acceptance as malt by focusing on increasing production of the diverse hydrolyzing enzymes utilized in the mash and reducing the abundance of storage proteins