banner 22. From raw materials to malts: Influence of the malting parameters on malt aroma development

C. L. ALMAGUER (1), M. Gastl (1), T. Becker (1); (1) TUM – Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany

Technical Session 7 - Malt and Grain
Tuesday, June 16
8:30–10:15 a.m.
Fiesta 3,4,6,8

Malting involves the controlled germination and subsequent drying (kilning) of cereal or pseudocereal grains. By varying the processing parameters during germination and drying, a variety of malts with different attributes is obtained. The brewer’s main requirement of malt is as a source of substrate, enzymes, and color; as a result traditional malting technology has developed to improve these properties. However, suitable manipulation of the malting conditions could positively enhance the aroma profile of malts as well as the sensory and nutritional properties of raw materials. Malt aroma is created based on the effects of the available combinations of amino acids and reducing sugars. These are available due to the kernel modification brought about by germination. The increased concentration of free sugars and essential amino acids provides a rich source of precursors for the key flavor generating reactions (e.g. Maillard reaction, Strecker degradation). Ultimately, the concentration and distribution of amino acids and reducing sugars in the modified grains determine the resulting aroma profile. In an attempt to understand the impact of the malting process on malt aroma development, three raw materials (barley, rye, and quinoa) were investigated and compared. This study focused on the influence of three malting parameters (temperature, germination time, and moisture) on the analytical and sensory properties of the produced malts. The experimental designed allowed the contribution of each factor, along with their interactions, to be assessed from an analytical perspective using the appropriate instrumentation (e.g. GC-FID). Changes in the aroma profile associated with the influence of the malting parameters were determined. In addition, a standard malt was produced for each of the raw materials used. The aroma profile of the produced standard malts was determined and the key aroma compounds were identified. To determine the key aroma compounds, different analytical methods were coupled. The volatile compounds were isolated by headspace solid-phase microextraction (SPME), solvent assisted flavor evaporation (SAFE), and simultaneous distillation/extraction (SDE); these were then analyzed with GC-MS/O. Aroma extract dilution analysis (AEDA) of the SAFE extracts was done to identify the key aroma compounds of each of the produced malts. The collected data allowed accurate disclosure of the volatile compounds responsible for the rye malt aroma, quinoa malt aroma, and barley malt aroma and comparison of them among each other. Compared to other aspects in malting, little attention has been given to the aroma development in malt. Small variations in the malting process can lead to a wide range of products with very different aroma characteristics. Understanding the impact of germination on aroma properties as well as increasing the knowledge on key malt aroma compounds is essential for an informed assessment of aroma development during malt production. The maltster and brewer, in turn, may benefit from proper selection of malting parameters to add subtle aromas and flavors to beers.

In 2008, Cynthia Almaguer completed her B.S. degree in biochemical engineering at Jacobs University Bremen. She then started her master’s degree in a collaborative project between the Institute of Brewing and Beverage Technology (Prof. Thomas Becker) at TUM-Weihenstephan and the Department of Food and Nutritional Sciences (Prof. Elke Arendt) at University College Cork. Her research project aimed to understand and reveal the taste and antimicrobial contributions of hop hard resins on beer. Her hop project was funded by the Barth-Haas Group. Cynthia is the 2010 recipient of the InBev-Baillet Latour Fund Scholarship for Brewing and Malting to fund her Ph.D. work. A significant portion of her current research activities are directed toward beverage development and the investigation and understanding of malt aroma.