Abstract 007
Origin and Formation of 2-Nonenal in Heated Beer
Tech. Quart., Master Brew. Assoc. Am. 13: 227-232, 1976
L.E. Stenroos, P.S. Wang, K.J. Siebert, and M.C. Meilgaard
Beer produces large amounts of 2-nonenal on heating at 100ºC and pH 2, and the same is true of a suspension of barley and linoleic acid. 3 isomeric trihydroxyoctadecenoic acids have been identified in the latter system, and were shown to be the major sources of nonenal production both in barley and in beer. 2 of the compounds were identified as Graveland’s compounds G1 and G2 [see FSTA (1972) 4 8H1258] while the third is a new compound which has the 3 hydroxy groups on adjacent carbon atoms, namely, 9,10,11-trihydroxy-12(trans)-octadecenoic acid. In pilot brewing, addition of linoleic acid to the mash greatly increased the amounts of nonenal precursors in the resulting beer. Brewing under N2, treatment of the wort with active C, and combinations of these treatments caused a reduction in the concn. of nonenal precursors, but this did not result in any improvement in flavour stability. It was shown that the trihydroxy acids, although they produce large amounts of 2-nonenal when boiled at pH 2, are too stable to break down in finished beer at its natural pH.
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