A Comprehensive Evaluation of Flavor Instability of Beer (Part 1): Influence of Release of Bound State Aldehydes

Abstract

Flavor instability of pale lager beer depends decisively on aroma-active aldehydes from the Maillard reaction, Strecker degradation, and lipid oxidation, which are formed in various oxidative and non-oxidative reactions. Therein, aldehydes can be formed de novo and be released from bound states to a free, aroma-active form during aging. During malting and brewing, proteolysis affects the amount of soluble nitrogen and thus flavor instability in different ways (e.g., precursors for de novo formation and binding agents for bound states). To isolate nitrogen-related aging processes, beers from malts (two barley varieties, three proteolytic malt modifications) were produced on a 50 L scale in part 1 of this study. Sensory analysis revealed increased flavor instability for beers with higher amounts of soluble nitrogen. Especially Strecker aldehydes significantly increased with malt modification. The release of bound state aldehydes revealed most free aldehydes in fresh beers and with higher malt modification. During aging, the equilibrium between free and bound state aldehydes shifted toward the free form. These results reveal a nitrogen-dependent bound pool of aldehydes that is depleted during aging and is responsible for aged aroma, especially in the early and medium stages of aging. Therefore, bound state aldehydes are indicators of the early-stage prediction of flavor instability already in a fresh condition.

A Review of N-Heterocycles: Mousy Off-Flavor in Sour Beer

“…Second, pyridines and pyrrolines can be Maillard and Strecker degrading products, which are formed during the kilning of malt, especially with higher roast levels. 48,52,53,63 Due to limited studies and analytical methods as well as complex processes and variables of different beverage matrices, it is unclear which pathways play a more significant role in forming mousy offflavor. 43−47 Spontaneously or mixed-culture fermentations have a higher risk of developing mousy off-flavor.…”

“…Innovation and competition among macro- and microbreweries increased subtle variations and experimentation in malt selectivity, hop varieties, brewing, and fermentation techniques. − As a result, a wide spectrum of unique tastes and aromas has increased along with off-flavors. Likewise, onion-like off-flavor which is caused by 2-mercapto-3-methyl-1-butanol (2M3MB) and 3-mercapto-3-methyl-1-butanol (3M3MB), aldehydes, e.g., acetaldehyde with “grassy” off-flavor if concentration is above 10–20 mg L –1 , and mousy off-flavor associated with N-heterocyclic abundance. − …”

“…First, APY, ATHP, and ETHP can develop from metabolic pathways involving microbial communities. Second, pyridines and pyrrolines can be Maillard and Strecker degrading products, which are formed during the kilning of malt, especially with higher roast levels. ,,, Due to limited studies and analytical methods as well as complex processes and variables of different beverage matrices, it is unclear which pathways play a more significant role in forming mousy off-flavor. − …”

Assessment of Staling Aldehydes in Lager Beer under Maritime Transport and Storage Conditions

“…More recently, it has been reported that during beer aging the release of bound-state aldehydes and their de novo formation occur simultaneously, although de novo formation during natural aging is more prevalent after four months [17]. Therefore, the presence of these carbonyl compounds, either in their free or bound state form, and their precursors for de novo formation, define the aging potential of the final beer, which can easily vary according to the brewing process and raw materials applied [18].…”

Cost-Effective and Portable Instrumentation to Enable Accurate pH Measurements for Global Industry 4.0 and Vertical Farming Applications

“…In fermentation processes, continuous quantification of the pH is relevant to avoid the generation of unwanted and harmful by-products [6][7][8]. In the brewing industry, the pH serves to determine aging, increments in hop hardness, and bittering concentrations [9][10][11]. For perishable products, such as meat and fish, the pH level reveals shelf life and freshness [12][13][14][15].…”