Identification of a new light-struck off-flavour in "light-stable" beers.
(2012) Cerevisia (Bilingual Edition) : Belgian journal of brewing and biotechnology — Vol. 37, p. 10-14 (2012)
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- Abstract
- For decades, MBT (3-methyl-2-buten-1-thiol) is known as the compound responsible for the lightstruck off-flavour in beer. This leads many brewers to adapt the procedures by using reduced hop extracts. Unfortunately, other off-flavours including onion-defects often characterize these “light stable” beers. In the present work, a commercial lager beer which did not contain isohumulones (blend of dihydroisoalpha acids; bottled in clear glass) was submitted to various natural aging. Whereas no MBT-defect (skunky-like) was detected by sensorial analyses, a strong “onion-like” off-flavour was evidenced in the samples exposed to light. GC-PFPD and GC-O analyses of global (XAD) and thiol specific (pHMB) extracts allowed us to identify 2-sulphanyl-3-methylbutanol (2S3MBol) as the key-off-flavour (AEDA Flavour Dilution = 32–1024 for 2S3MBol while only 8–64 for MBT). 2S3MBol revealed to be synthesized from 3-methyl-2-buten-1-ol (MBOH) found in hop extracts. The involved radicalar mechanism is strongly enhanced by light. Although reduced hop extracts improve light stability regarding MBT, aroma-extracts give rise to strong onion-like off-flavours in presence of light. The concentration of the hop allylic precursor should be monitored in commercial hop extracts.
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Gros, J., & Collin, S. (2012). Identification of a new light-struck off-flavour in “light-stable” beers. Cerevisia (Bilingual Edition) : Belgian journal of brewing and biotechnology, 37, 10-14. https://doi.org/10.1016/j.cervis.2012.04.003 (Original work published 2012)