Oxidative degradation of lipids during mashing

Area of Science:

• Food Chemistry
• Brewing Science
• Oxidative Stability

Background:

• Beer ingredients contain high concentrations of polyunsaturated fatty acids (PUFAs), prone to oxidation.
• Oxidation of PUFAs during brewing generates lipid-derived products, significantly reducing beer's taste and quality.
• Mashing is a critical stage where PUFAs are exposed to oxygen and heat, promoting off-flavor formation.

Purpose of the Study:

• To identify markers for oxidative damage to fatty acids during the mashing process.
• To investigate the role of enzymatic versus nonenzymatic oxidation in PUFA degradation during mashing.
• To determine the impact of oxygen tension on oxidative damage and antioxidant capacity in mashing mixtures.

Main Methods:

• Utilized F1 phytoprostanes (PPF1s) and monohydroxy fatty acids (OH-FAs) as biomarkers for oxidative damage.
• Analyzed the formation patterns of OH-FAs to differentiate between enzymatic and nonenzymatic oxidation pathways.
• Assessed changes in antioxidant capacity under varying oxygen tension levels during mashing.

Main Results:

• Enzymatic oxidation of PUFAs was identified as a more significant contributor to OH-FA formation than nonenzymatic oxidation.
• Substantial nonenzymatic radical formation was evidenced by increased levels of specific OH-FAs and PPF1s.
• Low oxygen tension was found to reduce oxidative damage and enhance the antioxidant capacity of the mashing mixture.

Conclusions:

• Mashing under low oxygen pressure is recommended to minimize oxidative damage to PUFAs.
• Controlling oxygen exposure during mashing is crucial for preventing lipid-derived off-flavors and maintaining beer quality.
• Understanding oxidation mechanisms in mashing provides insights for optimizing brewing processes.