Occurrence of polyfunctional thiols in sorghum beer "ikigage" made with Vernonia amygdalina "umubirizi"

Several polyfunctional thiols have been previously identified in beers made from barley and hops. These compounds have not been investigated in beers brewed with non-Western raw materials. Here we have performed a thiol-specific extraction with p-hydroxymercuribenzoic acid on a traditional ikigage sorghum beer from Rwandese peasants (use of Vernonia amygdalina just for yeast propagation), and on two pilot beers with addition (or not) of V. amygdalina in the boiling kettle, instead of hops. Gas chromatography – olfactometry, gas chromatography –mass spectrometry and gas chromatography with pulsed flame photometric
detectionanalyses of the extracts enabledustoidentify 14polyfunctional thiols.The well-known ho
pconstituent3-methyl-2-buten-1-thiol emerged as a key flavour in the unhopped beers containing V. amygdalina flavour dilution >262 144). The addition of V. amygdalina during boiling also resulted in the presence of 1-butanethiol, but the production of 2-sulfanylethanol and 2-sulfanylethyl acetate was inhibited. Complementary data are required to understand how V. amygdalina leaves are able to impact upon the Ehrlich pathway leading to cysteine and homocysteine-derived thiols.