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Malty flavor by nature? – Characterization of the biotransformations on malt aroma upon malting
C. ALMAGUER (1), M. Gastl (2), H. Kollmannsberger (2), T. Becker (2) (1) TUM – Institute of Brewing and Beverage Technology, Freising, Germany; (2) TUM – Institute of Brewing and Beverage Technology, , Germany.

To understand the impact of the malting process on malt aroma development, 3 raw materials (barley, rye, quinoa) with different functional properties were investigated and compared. First, the influence of 3 malting parameters (temperature, time, moisture) on the analytical, sensory and processing properties of the malts was examined. The experimental design allowed the contribution of each factor, along with their interactions, to be assessed from an analytical perspective. Subsequently, standard malting parameters for each grain, were selected based on the processing properties (extract=max; viscosity=min). A standard malt was produced for each of the grains analyzed. The daily modifications were monitored, under standard malting, and their impact on aroma formation was quantified (GC-FID). In barley, 3-methylbutanal (malty) decreased after day 4 by 15%, 2-phenylethanal (floral) only decreased after 5 days (22%). In rye malt, both compounds reached their highest concentration on day 6 and then decreased by 11% and 16%, respectively. Both compounds steadily increased in quinoa; at the end of germination no aroma loss occurred. In addition, the aroma profile of the standard malts was characterized and the key aroma compounds were identified. The volatile fraction was isolated by solvent assisted flavor evaporation (SAFE) and analyzed with GC-MS/O. Aroma extract dilution analysis (AEDA) of the SAFE extracts revealed 5, 6 and 8 odor-active compounds in barley, rye and quinoa, respectively. Among which 3-methylbutanal, 2-ethyl-3,5-dimethylpyrazine (roasted) and 2-methoxy-3-isopropylpyrazine (cucumber) predominated with the highest flavor dilution factors in barley, rye and quinoa, respectively. Understanding the impact of germination on aroma allows food and beverage manufacturers to add subtle aromas and flavors to products such as specialty malts, breads and beverages.