STRUCTURE ELUCIDATION OF THREE DIMERIC PROANTHOCYANIDINS ISOLATED FROM A COMMERCIAL BELGIAN PILSNER BEER

¹H n.m.r., mass spectrometry and circular dichroism of their methyl ether diacetates establish the structure of three dimeric beer proanthocyanidins as (2R, 3S, 4S; 2R, 3S)-{4,8}-bi-{(+)-catechin} (procyanidin B3), (2S, 3S, 4S; 2R, 3S)-{4,8}-{(+)-epigallocatechin-(+)-catechin} (prodelphinidin B9, novel compound) and (2R, 3S, 4S; 2R, 3S)-{(+)-gallocatechin-(+)-catechin} (prodelphinidin B3).     

INHIBITION AND ACTIVATION OF BARLEY PEPTIDE HYDROLASES II. PEPTIDE HYDROLASES B AND C,AND L-LEUCYL-β-NAPHTHYLAMIDASE

Peptide hydrolase B is inhibited by DIPF and appears to be a “serine esterase” enzyme. Para-chloromercuribenzoate is also inhibitory, but it acts irreversibly and not as a mercaptide former. Dithiothreitol acts irreversibly to inhibit the enzyme and thioglycolate is a weak, reversible inhibitor. Peptide hydrolase C is also inhibited by DIPF, and no consistent indication of metal ion or sulphydryl group involvement was observed. L-leucyl-β-naphthylamidase apears to be a metalloenzyme. It is mildly inhibited by some chelating agents and is stimulated by Ni²⁺ after prior treatment with EDTA. The enzyme is moderately inhibited by PCMPS and exhibits variable responses to different sulphydryl compounds.     

THE MILLING ENERGY OF MALTED BARLEY AND ITS RELATIONSHIP WITH HOT WATER EXTRACT AND α-AMYLASE ACTIVITY

Hot water extract is dependant on endosperm structure and its breakdown during malting. These endosperm characteristics can be rapidly assessed on 5 g samples by measuring the milling energy of malted barley. α-amylase determinations on the resultant flour indicate that good malting barleys have either moderate or high levels of the enzyme. High levels of α-amylase will not confer good malting quality where endosperm modification has proceeded slowly.     

AN ENZYMIC METHOD FOR THE MEASUREMENT OF TOTAL AND WATER-SOLUBLE β-GLUCAN IN BARLEY

Crude cellulase preparations from Trichoderma reesei, freed of amyloglucosidase by heating, will completely hydrolyse barley β-glucan to glucose. Apparent non-quantitative recovery of glucose is due to its adsorption by the high levels of protein present. Methods are given for the measurement of total and water-soluble β-glucan. Dehusking does not lower the amount of β-glucan which is measured.     

THE EBC METHODS FOR DETERMINATION OF HIGH MOLECULAR WEIGHT β-GLUCAN IN BARLEY,MALT, WORT AND BEER

Two new methods for the determination of β-glucan in barley, malt, wort and beer are accepted as EBC Standard Methods for β-glucan by the Analysis Committee of the European Brewery Convention. One method (The fluorimetric method) is based upon the specific interaction of the fluorochrome Calcofluor towards high molecular weight β-glucan. The method is suitable where a high number of determinations have to be done routinely. The other method (The enzymatic method) utilizes a specific degradation of the β-glucan by purified enzymes. This method is more laborious, but it can be carried out using apparatus available in an analytical laboratory. The methods, which are described in detail, have been tested in a EBC Collaborative Test with 14 participating laboratories. Barley, malt and beer samples at 6 levels of concentration were tested for β-glucan. The collaborative test resulted in acceptable statistical values for repeatability and reproductibility for both methods. Comparison of the results from the two methods, showed that they are highly correlated and that the actual values of β-glucan content are comparable.     

EVALUATION OF MALTING QUALITY IN A BARLEY BREEDING PROGRAMME USE OF α-AMYLASE AND β-GLUCAN LEVLES IN MALT AS PRESELECTION TOOLS

Analysis according to the EBC protocol, immunological determination of a α-amylase and estimation of malt β-glucan using the Calcofluor-FIA method, were used to screen 327 barley breeding lines for malting quality. The results obtained with the α-amylase and β-glucan methods are highly correlated to the important malt quality paramters: extract yield and β-glucan content in the wort. It is recommended that either of the two methods, which are simple to perform are used as prescreening tools in breeding programmes for malting barley.