Nature and occurrence of free polyfunctional thiols in spices used in brewery
Files
Tyckaert_80002000_2025.pdf
Closed access - Adobe PDF
- 3.86 MB
Details
- Supervisors
- Faculty
- Degree label
- Abstract
- Polyfunctional thiols (PFTs) are among the most powerful aroma compounds due to their very low odor thresholds. While their occurrence is well documented in hops and grapes, their presence in culinary spices has rarely been investigated despite the chemical richness of these matrices and their potential applications in brewing, distilling and flavor formulation. The aim of this work is to characterize the diversity, abundance and possible biosynthetic origins of free PFTs in nine selected spices and to compare their profiles with those of hops. For this purpose, two different samples of bitter orange, cardamom, cinnamon, clove, coriander, ginger, hibiscus, licorice and star anise were analyzed. Free thiols were by silver ion solid-phase extraction (Ag-SPE) and eluted with cysteine solution. After concentration, they we analyzed by gas chromatography coupled with a pulsed flame photometric detector (GC-PFPD) using two columns of different polarity for retention index comparison and identification. Across several spices, two compounds were found to be consistently dominant, 3- sulfanyl-4-methylpentyl acetate (3S4MPA) and 3-sulfanyloctan-1-ol (3SOol), were detected at concentrations sometimes comparable to or higher than those reported for hops, imparting intense grapefruit and citrus notes. Other recurrent thiols, such as 3-sulfanylpropan-1-ol (3SProl), 3-sulfanyl-2-ethylpropyl acetate (3S2EPrA) and 3-sulfanyl-2-methylbutyl acetate (3S2MBA), contributed to a broader aromatic palette ranging from floral and fruity to vegetal and vinegar-like notes. Pronounced differences on the ratio of acetate esters to alcohol thiols were observed between spices, suggesting variable acetyltransferase activity. Marked inter-sample variability also reflected the influence of harvest year, geographical origin, processing and storage conditions. Biosynthetic interpretation indicated that in spices, aldol condensation involving acetaldehyde and formaldehyde, followed by glutathione conjugation, reduction and sometimes acetylation, may represent a major pathway for PFT formation. This contrasts with the lipid oxidation pathways more frequently proposed for hops and grapes.