Understanding malt aging – how old is too old?

By Harmonie Bettenhausen, Director, Hartwick College Center for Craft Food & Beverage

Barley has a long journey from seedling to beverage (beer, spirit, etc.), but once it becomes malt, it can spend months or years in storage waiting to be mashed. With the assistance and collaborative efforts of Colorado State University, UC-Davis, Admiral Malting, and Colorado Malting Company, and financial support from AMBA and the American Society of Brewing Chemists (ASBC), we have identified a gap in our knowledge regarding the dynamics of malt chemistry during storage. Malt quality is defined by the chemical characteristics which influence fermentation and brewing. However, after the malting process, the chemistry of the malt will continue to slowly change over time. We realized that aging malt, even under proper storage conditions, is exposed to oxygen and can lead to specific chemical processes (e.g. lipid oxidation which leads to rancidity), eventually yielding degraded quality.

Previous research in this area has focused on the use of metabolomics to investigate the chemical profile of barley, malt, and beer and the relationships to genetics, quality, and flavor. Metabolomics is the study of the unique small-molecule profiles that specific cellular processes leave behind. The chemical profile (metabolome) of barley, malt, and beer is very diverse and includes lipids, proteins, carbohydrates, and volatile compounds. This type of investigation allows us to look at an instantaneous snapshot of the physiology of barley (or malt or beer), using chromatography (liquid or gas are used as a medium to help us separate molecules of interest) and mass spectrometry (the measurement of masses of molecules of interest). The chemical profile of aging malt can help us to find clues about our questions:

  1. In what ways does the metabolome composition of malt change over time?
  2. How rapidly does the composition change?
  3. Can we predict a ‘ripe’ stage for malt using our metabolite fingerprinting methods?
  4. Are malting quality analyses valid after long-term storage and aging of the malt?

Through our collaboration with Admiral Maltings and Colorado Malting Company, we were able to set up a real-time aging experiment under commercial conditions. At three time points, the aging malt was then brewed by the team at UC-Davis, malting quality analysis was performed by Hartwick College Center for Craft Food and Beverage. Sensory analysis of beer was performed in two settings – at The Rake at Admiral Maltings by a consumer panel and at Lagunitas Brewery (Petaluma, CA) by a trained panel. Sensory data, along with the quality and chemical profiling results, will lead us to the major outputs of our study; helping us discover the types of metabolites that are affected by storage and potential effects of storage time and conditions on brewing quality and flavor. Impacts on breeding, malting, and brewing programs could be significant if the markers to optimize malt quality for brewing in the context of storage are better understood. Those results will be shared at the conclusion of the research.