A series of natural methyl thio esters: methyl thiopropionate (FEMA# 4172, CAS# 5925-75-7), methyl thiobutyrate (FEMA# 3310, CAS# 2432-51-1), methyl thioisovalerate (FEMA# 3864, CAS# 23747-45-7) and methyl thiohexanoate).
The range occurs naturally in aged cheeses including cheddar and camembert. Characteristics include cheesy, fermented, sulfurous, cooked allium and tropical and overripe fruit at levels of 2.0 ppm to 5.0 ppm.