The Influence of Heavy Metal Ions on Beer Flavour Stability

Abstract

In this study, the importance of iron and copper ions and their radical formation via the respective Fenton and Haber-Weiss reactions was confirmed. Of the other heavy metals present in the brewing process in relevant concentrations, the impact of manganese ions on beer flavour stability has been elucidated. In contrast to iron and copper, manganese ions are not removed from wort or beer to any great extent during the process. Additionally, manganese shows a similar radical-promoting effect to that seen with iron and copper. Its reactivity, and typically higher concentration than the other two metals in beer, appear to make manganese an especially potent pro-oxidant in beer. The results of the investigation clearly indicate that there are other heavy metals influencing the stale flavour characteristics of beer, in addition to the well-known metals, iron and copper. In contrast to the aforementioned ions, manganese does not enter the product by being leached out of a tank or from piping materials, but rather comes from the cereals employed in brewing. This finding, concerning the importance of manganese as a redox system in beer staling, can serve as a basis for a different approach in the choice of raw materials.

Effect of wheat malt on the concentration of metal ions in wort and brewhouse by-products

“…Fe, Mn 2+ ) negatively impact the process, inducing free radical formation (7), which results in a deterioration of flavour during storage (3). The metal ion content of the wort depends mainly on the quality of the raw materials (barley malt, water and hops).…”

“…The ionic composition of brewer's wort is an important factor that influences the fermentation process and beer quality (1)(2)(3). Some ions (e.g.…”

125th Anniversary Review: The Non-Biological Instability of Beer

“…It has been observed, however, that even in the absence of lipoxygenase, unsaturated fatty acids can be degraded through the action of reactive oxygen species 20 . Oxygen activation is effected by metal ions, notable iron and copper 18 , although it has recently been suggested that manganese, derived from malt, may be at least as relevant 168 . Irrespective of whether oxidation of unsaturated fatty acids is enzyme-driven or non-enzymic, the minimization of oxygen levels in the mash would be beneficial.…”

Indigo carmine degradation in the presence of maltose and ethanol

“…They are active in both anaerobic and aerobic environments, but their effectiveness is higher under aerobic conditions. Activation of oxygen by metal can also support OFR formation (12,13).…”