Identification and Synthesis of 2-Heptanethiol, a New Flavor Compound Found in Bell Peppers

Abstract

2-Heptanethiol was identified for the first time as a constituent of red and green bell pepper extracts. The chemical structure of this new aroma compound was proposed on the basis of mass spectra and retention indices and confirmed by chemical synthesis and nuclear magnetic resonance spectroscopy measurements. Its aroma properties were described as sulfury, onion-like, and vegetable-like, reminiscent of bell pepper at lower concentrations, with an orthonasal detection threshold of 10 microg/L of water. No differences in odor note and threshold value were observed for the enantiomeric forms, which were prepared from enantiopure 2-heptanol by tosylation, followed by thioacetylation and reduction, giving the target thiol enantiomers.

Volatile and capsaicinoid composition of ají (Capsicum baccatum) and rocoto (Capsicum pubescens), two Andean species of chile peppers

“…2‐Heptanethiol was described as green, kerosene/paprika‐like during the sniffing runs. This description might be similar to the sulfury, onion/vegetable‐like impressions reported by Simian et al 40 Its aroma was recorded in most studied accessions, although the highest impressions corresponded to C. baccatum (Table 5). Furthermore, two pyrazines, 3‐ sec ‐butyl‐2‐methoxypyrazine and 3‐isopropyl‐2‐methoxypyrazine, contributed uniquely to the aroma of rocotos with their earthy and green/peasy notes.…”

“… b Reliability of identification: R, identified by comparison of mass spectrum and RI with authentic reference substance; MS, tentatively identified by mass spectrum; L, tentatively identified by comparison of mass spectrum and RI with literature 40…”

The Significance of Volatile Sulfur Compounds in Food Flavors

“…2-Heptanethiol was recently reported as a new flavor compound in cooked red and green bell peppers (86). Subsequently, a series of newly-reported thiols, mercapto ketones, mercapto alcohols, and methylthio-thiols were identified in red bell pepper which cover a palette of organoleptic properties (15).…”

The role of cysteine and cysteine–S conjugates as odour precursors in the flavour and fragrance industry

“…116,117 Our results showed that there is the expected corresponding cysteine-S conjugate 75 in green bell pepper and that it was present at 0.09 mg/ kg. 120 Although the characteristic aromas of bell pepper can be identified by smell alone, the intensity and persistent perception of the volatile thiols was increased upon ingestion of 75 by a sensory panel. 65 Cat urine…”