Which chemical compound is responsible for the smell of asparagus, coffee, and onion?

Which chemical compound is responsible for the smell of asparagus, coffee, and onion?

• A. Esters
• B. Thiols (methanethil, 2-furanmethanthiol, and benzenemethanthiol)
• C. Amines - indole (purescine, cadaverine)
• D. Ketones

Answer: (B)

Smell in asparagus, coffee, and onion comes from sulfur-containing compounds called thiols. The key feature of these molecules is the -SH group, which makes them extremely potent odorants even at very low concentrations. When onions are cut, enzymes convert sulfur-containing precursors into volatile thiols that sweep through the air and create that sharp onion aroma. In coffee, roasting generates a variety of sulfur compounds, and some of the most impactful are thiols like 2-furanmethanthiol and related structures, which contribute distinctly strong, coffee-like notes. Methanethiol itself is a simple, highly noticeable thiol, and benzenemethanethiol adds another sulfur-containing aroma contributor. That combination of volatile thiols explains the pronounced, sulfurous smells associated with these foods. Other classes don’t fit as well. Esters tend to give fruity scents, amines and related compounds like indole and cadaverine carry rotten or fecal-type odors, and ketones produce a wide range of smells but not the characteristic sulfur-driven notes seen here.

Smell in asparagus, coffee, and onion comes from sulfur-containing compounds called thiols. The key feature of these molecules is the -SH group, which makes them extremely potent odorants even at very low concentrations. When onions are cut, enzymes convert sulfur-containing precursors into volatile thiols that sweep through the air and create that sharp onion aroma. In coffee, roasting generates a variety of sulfur compounds, and some of the most impactful are thiols like 2-furanmethanthiol and related structures, which contribute distinctly strong, coffee-like notes. Methanethiol itself is a simple, highly noticeable thiol, and benzenemethanethiol adds another sulfur-containing aroma contributor. That combination of volatile thiols explains the pronounced, sulfurous smells associated with these foods.

Other classes don’t fit as well. Esters tend to give fruity scents, amines and related compounds like indole and cadaverine carry rotten or fecal-type odors, and ketones produce a wide range of smells but not the characteristic sulfur-driven notes seen here.