A number of potential antioxidants have been evaluated for their effect on formation of radicals in beer using the electron spin resonance (ESR) lag phase method. Sulfite was found to be the only compound that was able to delay the formation of radicals, whereas phenolic compounds such as phenolic acids, catechin, epicatechin, and proanthocyanidin dimers had no effect on the formation of radicals. Ascorbate, cystein, and cysteamin were on the other hand found to be prooxidants. It is suggested that antioxidants must be able to either scavenge peroxides or trap metal ions in order to be effective in beer. The effectiveness of sulfite is suggested to be a consequence of its two-electron nonradical producing reaction with peroxides.

A vanillin-HCl staining has been used to locate the proanthocyanidins in mature barley grains. These flavanoids were found to be concentrated in the seed coat (testa) just outside the aleurone layer in the 7 varieties with yellow coloured grains investigated. The seed coats of 10 proanthocyanidin-free barley mutants belonging to 4 different gene loci did not stain with vanillin-HC1.

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In the present paper the composition of proanthocyanidins isolated from barley is investigated. Separation by affinity chromatography and HPLC yields a large number of substances. Six of these have been isolated in this work. Based on the chromatographic preparation they are expected to be two dimers DI and D2 and four trimeric substances TI -T4. Studies by means of IH NMR spectroscopy at 270 MHz confirmed DI and D2 as being dimeric compounds, a prodelphinidin and procyanidin B3 respectively. The spatial structure of the prodelphinidin corresponds to procyanidin B3. The peracetates of all six compounds have also been studied by means of IH NMR spectrocopy. By comparison with data for the analogous peracetates of (+)-catechin and (-)-epicatechin and with literature data, T1 -T4 have been identified as trimeric proanthocyanidins and their structures have been elucidated.

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