Copper Binding in Sweet Worts Made from Specialty Malts

Area of Science:

• Food Chemistry
• Brewing Science
• Analytical Chemistry

Background:

• Trace copper significantly influences beer flavor stability.
• Malt is the primary source of copper in beer wort.
• Copper levels are determined during mashing and lautering processes.

Purpose of the Study:

• Investigate copper(II) (Cu(II)) binding in sweet worts from experimental roasted and caramel malts.
• Assess the impact of Cu(II) ions on wort oxidative stability.
• Identify key copper chelators in wort.

Main Methods:

• Potentiometric titrations using ion-selective electrodes.
• Electron paramagnetic resonance (EPR) spectroscopy.
• Analysis of sweet worts from experimental roasted and caramel malts.

Main Results:

• High-temperature malting decreased Cu(II) binding affinities.
• Roasted malt worts exhibited lower Cu(II) binding affinities than caramel malt worts.
• Dipeptides were identified as the primary Cu(II) chelators, correlating with free amino nitrogen levels.
• Cu(II) demonstrated antioxidative effects in dark worts and moderate prooxidative effects in pale worts.

Conclusions:

• Malting conditions, particularly high-temperature treatments, alter copper's interaction with wort components.
• Copper's role in wort oxidation is context-dependent, acting as an antioxidant in dark worts and a prooxidant in pale worts.
• Understanding copper binding is crucial for managing flavor stability in beer.