Steam volatile components of roasted barley

Abstract

Gas-liquid chromatography was used to examine the steam-volatile fraction of roasted barley. Ethanal, propanal,* 2-methylpropanal, 2-methylbutanal, 3methylbutanal, pentanal,* hexanal,* furfural, propanone, butanone, 2,3-butanedione,* 2,3-pentanedione, ethanol,* and pentanol* were identified in the headspace. Pyridine, pyrazine,* methylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine,* trimethylpyrazine, 2-ethyl-3-methylpyrazine,* 2-ethyl-5-methylpyrazine, 2,5-dimethyl-3-ethylpyrazine,* and 3,5-dimethyl-2-ethylpyrazine* were found in the basic fraction. Flavor aspects are discussed. The compounds with an asterisk have not previously been reported as present in roasted barley.Roasted barley is sometimes used to provide the desired color in dark beers.

Pyrazines in foods

“…However, if the compounds normally lost during this boil-off were trapped, and refluxed back into the product, the beer developed strong pyrazine-Hke flavor which was found to be objectionable. In conjunction with this observation, Collins (1971) 62…”

“…Later, Collins (1971) identified four additional pyrazines in roasted barley. The specific pyrazines found in both of these studies are listed in Table 3.…”

“…The specific pyrazines found in both of these studies are listed in Table 3. Interestingly, Collins (1971) used a roasting TABLE 2 Pyrazines Reported in Bakery Products pyrazine methylpyrazine 2,3-dimethylpyrazine 2,5-dimethyIpyrazine ethylpyrazine trimethylpyrazine 2-ethyl-3-methylpyrazine 2-ethyl-6-methylpyrazine propylpyrazine 2-methyl-5-propylpyrazine 3-methyl-2,5-dimethylpyraz vinylpyrazine 2-vinyl-6-methylpyrazine TABLE 3 Pyrazines Reported in Roasted Barley pyrazine methylpyrazine 2,3-dimethylpyrazine 2,5-dimethylpyrazine trimethylpyrazine 2-ethyl-3-methylpyrazine 2-ethyI-5-methylpyrazine 2,5-dimethyl-3-ethylpyrazine 3,5-dimethyl-2-ethylpyrazine…”

“…However, flowrate is critical since if too much product is admitted into the system at once, complete volatile removal is not achieved and if not enough sample is introduced, burn-on may result. Collins (1971) assumed that since pyrazines are readily soluble in water, there was no need to steam distill the entire food system. Thus, he leached the pyrazines out of ground roasted barley by permitting the barley to stand in water for 1 hr at 66°C and then filtering.…”

“…Another interesting pyrazine threshold study has appeared in the literature (Collins, 1971). This study dealt with the pyrazines found in roasted barley and their possible contribution to the flavor of dark Irish beer.…”