Aldehyde-induced xanthine oxidase activity in raw milk

Area of Science:

• Food Chemistry
• Dairy Science
• Oxidative Stress

Background:

• Xanthine oxidase (XO) is an enzyme present in milk that can contribute to oxidative processes.
• Aldehydes are compounds that can be formed during food processing and storage, potentially influencing oxidative stability.
• Understanding factors that accelerate oxidation in raw milk is crucial for maintaining dairy product quality and shelf-life.

Purpose of the Study:

• To investigate the pro-oxidative activity of various aldehydes on xanthine oxidase in a raw milk system.
• To elucidate the role of aldehydes in initiating radical reactions and superoxide formation in milk.
• To determine if aldehydes can accelerate oxidative events in milk via xanthine oxidase activation.

Main Methods:

• Utilized spin-trap electron spin resonance (ESR) spectroscopy to monitor aldehyde-induced pro-oxidative activity of xanthine oxidase.
• Tested a range of aldehydes (acetaldehyde, propanal, hexanal, etc.) in an accelerated raw milk system.
• Employed an ultrahigh temperature (UHT) milk model system with added xanthine oxidase to confirm superoxide formation.

Main Results:

• All tested aldehydes initiated radical reactions when added to milk.
• Aldehydes triggered superoxide formation in a UHT milk model system with xanthine oxidase, suggesting this as the initial reaction.
• Aldehyde addition increased ascorbyl radical concentration, followed by ascorbate depletion, confirming superoxide generation.

Conclusions:

• Aldehydes can induce pro-oxidative activity of xanthine oxidase in milk.
• This aldehyde-induced xanthine oxidase activity leads to the formation of superoxide radicals.
• The study demonstrates for the first time that aldehydes can potentially accelerate oxidative events in milk through this mechanism.