3-Mercapto-2-methylpentan-1-ol, a new powerful aroma compound

Area of Science:

• Food Chemistry
• Flavor Science
• Organic Chemistry

Background:

• Sulfur compounds are key contributors to the aroma of alliums like onions.
• Complex flavor profiles arise from numerous volatile compounds, often formed during processing.
• The specific chemical structures and sensory contributions of many onion volatiles remain uncharacterized.

Purpose of the Study:

• To identify and characterize novel flavor compounds in raw onions and thermally processed flavors.
• To elucidate the sensory properties and concentration-dependent impact of newly identified compounds.
• To propose a formation pathway for these compounds in onions.

Main Methods:

• Isolation and purification of volatile compounds from raw onion and processed flavor matrices.
• Structure elucidation using Mass Spectrometry (MS) and Proton Nuclear Magnetic Resonance ((1)H NMR).
• Chemical synthesis of proposed structures for confirmation.
• Sensory evaluation (olfactory assessment) at various concentrations.

Main Results:

• 3-Mercapto-2-methylpentan-1-ol was identified as a novel flavor compound, isolated from raw onions and processed flavors.
• The compound's odor profile is concentration-dependent, exhibiting pleasant meat broth, sweaty, onion, and leek-like notes at 0.5 ppb.
• 3-Mercapto-2-methylpentanal was proposed as an intermediate and confirmed as a new, potent flavor compound present in raw onions.

Conclusions:

• 3-Mercapto-2-methylpentan-1-ol is a significant contributor to onion and processed flavor aroma.
• The concentration of this sulfur compound critically influences the perceived flavor quality.
• A potential biosynthetic pathway involving 3-mercapto-2-methylpentanal has been proposed for onion volatiles.