Analytical Methods for Polyphenols in Brewing. V. Chromatography and Spectroscopy of Tanninogens in Malt and Beer¹

1 Presented at the 42nd Annual Meeting, Milwaukee, May 1976.

Abstract

A 50% aqueous-ethanolic extract of malt was partially dissolved in methanol and the insoluble residue acetylated. The products of acetylation were taken up in chloroform and chromatographed on silica gel. The chloroform eluate was subjected to preparative thin-layer chromatography (TLC) on silica gel yielding a number of phenolics. Acetylated (+)-catechin, (–)-epicatechin, and procyanidins B were identified by comparing their nuclear magnetic resonance (NMR) spectra with those of the synthetic reference compounds. In another procedure, the 50% aqueous-ethanolic malt extract was treated with water and the insoluble portion triturated with methanol. The residue was fractionated by acetone extraction and the two portions (soluble and insoluble) were acetylated. Procyanidins of B and A types were identified by NMR after TLC separation on silica gel. Beer was extracted with ethyl acetate, and procyanidins of B and A types were identified by NMR following acetylation and TLC. In another procedure, beer was passed through Nylon-66, and procyanidin B-3 and a catechin trimer were identified by NMR following extraction, chromatography on Sephadex LH-20, and acetylation. Desorption of Nylon-66 beer tanninogen adsorbate was also performed by using 50% aqueous dimethylformamide.

• Beer
• Chromatography
• Malt
• Nuclear magnetic resonance
• Tanninogens