Low molecular-weight phenolic compounds in natural and agglomerated cork stoppers

The low molecular-weight phenolic compounds in cork stoppers used for the c losure of wine bottles are studied. Different phenolic acids (gallic, proto catechuic, vanillic, caffeic, ferulic and ellagic), aldehydes (protocatechu ic, p-hydroxybenzoic, vanillin, ethylvanillin and coniferilic), and coumari ns (aesculetin and scopoletin) were determined in natural cork stoppers (un treated and chlorine-bleached) and in agglomerated cork stoppers (unbleache d and peroxide-bleached). The ketone 2,3-dihydroxy-1-guaiacylpropan-1-one a nd four ellagic-acid-type tannins were detected in natural stoppers. The am ount of most of the phenolic compounds studied was higher in the natural co rk stoppers than in agglomerated stoppers. In natural cork stoppers, an Inc rease in the content of caffeic and ferulic acids and vanillin was observed after chlorine bleaching. In agglomerated stoppers however, peroxide bleac hing produced a decrease in the content of these same compounds.