AMINO ACID ESTERS IN BEER

The ethyl esters of valine, leucine and iso-leucine have been detected in a range of commercial and experimental beers at levels between ca. 3 ppb and 71 ppb. However these compounds have been shown to have no noticeable effect on beer flavour at levels up to at least 12 ppm.     

AMINO ACID ANALYSIS OF BEER POLYPEPTIDES

The principles of amino acid analysis of proteins and polypeptides are reviewed. Analysis of the amino acid composition of dialysed beer material prepared from a wide variety of commercial and pilot brewery beers showed that the principal amino acids comprised glutamic acid/glutamine, proline, glycine and aspartic acid/asparagine. The results from the analysis of a series of pilot brewery beers brewed under standardised conditions showed that the composition of the grist may influence the amino acid composition of beer polypeptide fractions. Dialysed beer material prepared from beer brewed from grists containing torrified wheat, wheat flour and malted wheat contained greater proportions of glutamic acid/glutamine compared to material prepared from all malt beers. Further fractionation and analysis of dialysed beer material prepared from pilot brewery beers suggested that fractions MW>60000 contained polypeptide material derived from yeast mannan-protein. In addition fractions MW>60000 prepared from beer brewed from grists containing torrified wheat, wheat flour or all malted wheat may contain high molecular weight polypeptide material derived from wheat proteins. The results from the analysis of fraction MW 40,000–60000 prepared from beers brewed from grists containing all malt, 80% malt and 20% torrified wheat and 50% malt and 50% malted wheat are consistent with the presence of polypeptide material derived from cereal albumins and globulins whereas fractions MW 40,000–60000 prepared from beers brewed from 80% malt and 20% wheat flour and 100% malted wheat may contain polypeptide material derived from wheat prolamins and glutelins. The amino acid composition of fraction MW 20,000–40,000 from all pilot brewery beers investigated is consistent with the presence of polypeptide material derived from cereal prolamins and glutelins. The amino acid composition of beer polypeptide fractions may be used to detect the use of wheat adjuncts in beer brewing.     

NUCLEOTIDES IN BEER

Nucleotidic material was isolated by anion exchange chromatography of beer on a Dowex 1 × 8 (formate) column. Ultraviolet spectroscopy and retention volume data suggested the presence of cytidine monophosphate (CMP) [max. 5 mg/litre], in one of the fractions. No other mononucleotides were detected. Chromatography of charcoal extracts of beer on DEAE Sephadex A25 failed to yield a fraction containing mononucleotides. Triangular taste tests indicated that addition of adenosine-5′-monophosphate (AMP) and guanosine-5′-monophosphate (GMP) to beer (30 mg/litre and 25 mg/litre respectively) did not cause significant flavour changes.     

巴伐利亚啤酒生活

就像瓷器使人联想到中国、樱花使人想到日本、牛仔使人想到美国一样,啤酒让人想起的是德国。在德国,啤酒不是酒,而是日尔曼名族的范畴学。在标准的德国公司里．总会有一个置放饮料的冰箱,里面放着各种花色类型的啤酒。而上班时间喝这些饮料．也不会被认为是不合适。如果你问德国人,这些范畴学的发源地是哪儿？他们会说——“啤酒的巴伐利亚”．因为那里不仅有悠久历史、古老的传说和各式酿制方法,还有专属于啤酒的节庆和舞蹈。     

BEER PACKAGING IN CAN

The food can had its origins in the early nineteenth century and underwent continuous and substantial development prior to its introduction as a beer container in the nineteen thirties. Since then methods of manufacture have changed considerably, always with the aim of increasing efficiency and reducing cost. The modern beer can is a cheap, attractive and lightweight container requiring strict quality control to maintain the necessary high standards.     

DEXTRINS IN SORGHUM BEER

Dextrins containing from 4 to 10 glucose units were determined in sorghum malt, wort and beer by means of HPLC. Throughout a malting period of 10 days approximately 5% fermentable sugars and only trace amounts of dextrins could be detected and the pattern remained constant. During mashing, using maize adjunct and at pH 4, there was a rapid build-up of a wide range of dextrins but their content was greatly reduced during the final stages of mashing. Both sorghum and barley beer contained similar amounts of dextrins containing 4 to 9 glucose units. The majority of these dextrins was branched as their concentration was reduced to a great extent by the action of pullulanase. Dextrins containing more than 10 glucose units were detected and their concentration was also diminished by pullulanase.     

INTERPRETATION OF ULTRAVIOLET ABSORPTION IN WORT AND BEER. THE MAJOR ROLE OF NUCLEIC ACID DERIVATIVES

Total ultraviolet-absorbing constituents of wort and beer are partially resolved by direct gel column analysis, with continuous monitoring of effluent at 280 nm. The elution profile enables routine assessment to be made of the protein-phenolic fraction, of nucleic acid derivatives and of tryptophan, together with a measure of the generally low level of monomeric phenolics. The major portion of total ultraviolet absorbance in these brewing materials is apparently due to nucleic acid derivatives, which originate from the mashing process.     

THE ACTION OF NISIN ON BEER SPOILAGE LACTIC ACID BACTERIA

Within one minute of adding nisin to suspensions of Lactobacilli clumping of cells was observed. This happened with all the strains assayed, irrespective of their sensitivity or resistance to nisin. There was, however, no evidence of cell lysis. Two different assays for cell viability were used to show that the vast majority of cells of sensitive strains were killed within one minute of contact with nisin. The time needed to kill all the cells depended on the concentrations of both nisin and cells. One strain was more resistant and only 50–60% of the cells died within one minute of nisin addition . Using an ATP-bioluminescence assay it was shown that the addition of nisin to both Lactobacilli and Pediococci caused a rapid fall in intracellular ATP levels, which was reflected in a simultaneous appearance of ATP in the extracellular medium. Actively growing cells lost ATP more rapidly than did those in stationary phase. The amount of intracellular ATP lost was affected both by the concentration of nisin used and the sensitivity of the bacteria. It appears that an initial effect of nisin is to make the cell membrane ‘leaky’ as happens with many antibiotics, yeast killer factors (zymocins), colicins, and other gram-positive bacteriocins .     

RADIOIMMUNOASSAY OF PAPAIN IN BEER

A radioimmunoassay (RIA) of papain is described which is capable of detecting 0·2 μg of papain/ml in beer, a level approximately 1% of that normally used for chillproofing. Changes in incubation conditions significantly accelerates the papain determination with only slight loss of accuracy. Apart from the high sensitivity it has been shown that the method is highly specific and distinguishes papain from the other chillproofing enzymes used.     

NITROSAMINES IN MALT AND BEER

A brief account is given of the co-operation between the malting and brewing industries and the Ministry of Agriculture, Fisheries and Food in solving the NDMA problem in beer. The formation and removal of NDMA during processing is discussed with emphasis on methods used commercially to limit NDMA in the products.     

DETERMINATION OF LEAD IN BEER

Three procedures for the determination of low levels of lead in beer were evaluated and compared. The methods were (1) the existing IOB recommended procedure, (2) a dry ashing/AAS procedure and (3) a mixed solvent (xylene/2-heptanone) extraction of the DDDC complex. All three methods gave satisfactory results.     

VARIATIONS AMONGST BEERS AND LACTIC ACID BACTERIA RELATING TO BEER SPOILAGE

The ability of lactic acid bacteria to grow in beer has been studied using 31 beers, 13 strains of Lactobacillus and 3 strains of Pediococcus isolated from wort or beer. In 3 beers all the micro-organisms were able to grow, in 5 beers none of them developed and diverse results were obtained with the remaining 23 beers. Resistance of the beers to spoilage was not correlated with values of pH, specific gravity, total or free amino nitrogen, individual or total fermentable sugars, colour or levels of sulphur dioxide. Resistant beers became sensitive after certain filtration treatments and after heating at 80° for 15 minutes, but not after treatment at 60°. Resistance to spoilage is tentatively attributed to the presence of a yeast metabolite which is heat-labile. The lactic acid bacteria varied in their ability to grow in beer but those possessing a broad range of biochemical abilities had the greater propensity to cause spoilage.     

MEASUREMENT OF RESIDUAL CARBOHYDRATE IN BEER

No standardized method exists for the determination of total or individual carbohydrates in beer and this could cause difficulties in view of regulatory requirements for labelling. A comparative study of known methods likely to be most suitable for the measurement of total carbohydrate in beer was therefore undertaken. Methods were also examined for estimating other important residual carbohydrates in beer, such as residual fermentable carbohydrates, β-glucan, total fructose and fructosans, and total pentose and pentosans. The beers analysed covered a wide range of carbohydrate levels and, as expected, the different methods gave different values for the carbohydrate content of the same beer. We consider that the colorimetric anthrone-sulphuric acid procedure (Yadav's version) is to be preferred for estimating the total residual carbohydrate content of beer. It is less prone to interference, relatively simple, rapid and gives more accurate results than acid or enzymic hydrolysis in combination with reductometric procedures. The within-laboratory coefficient of variation is 1.68%.     

HAZE- AND FOAM-FORMING SUBSTANCES IN BEER

A study of recent literature on haze- and foam-forming substances in beer suggests the following picture: Traces of true protein, apparently above 150,000 in molecular weight (MW), exist in beer. Apart from these, the main complex nitrogenous substances are present in compounds in the 5,000–70,000 MW region. Nevertheless, these are not proteins, but amino-acid complexes (proteoses) coupled with non-nitrogenous substances. As is well known, haze and haze precursors are proteoses coupled with polyphenols. These two species can be joined by hydrogen bonds to give compounds which are readily dissociated. However, a much firmer, covalent, linkage can be formed. This type of linkage arises from oxidation of polyphenols to quinones, which in turn can oxidize and couple with several groupings on proteoses. One of the most probable points of attack is the sulphydryl group of cystine, and the relatively high percentage of cystine in haze indicates that this occurs. It seems likely that this reaction, to form acidic complexes, occurs mainly in the initial stages of mashing and boiling. In beer, further coupling between pairs or triplets of polyphenolic or quinolic groupings can take the products into the very high molecular weight region of hazes. Correspondingly, the foam-enhancing proteoses tend to be lower in cystine content and to show less combination with polyphenols. However, they too are largely in the form of complexes and the evidence suggests that here the proteoses are mainly combined with glucose polymers, a reaction which takes place during kilning and possibly during boiling. These complexes are less acidic than the polyphenolic ones and tend to be rather lower in molecular weight. Suggestions arising from these concepts may be helpful in controlling the haze and foam potentialities of beers.     

DETERMINATION OF TOTAL CARBOHYDRATE IN BEER

A colorimetric procedure for the determination of total carbohydrate in beer has been evaluated in a collaborative trial. The method is recommended by the Analysis Committee.     

DETERMINATION OF CARBON DIOXIDE IN BEER

A rapid, simple and inexpensive method is described for the determination of the carbon dioxide content of beers.     

THE ESTIMATION OF p-HYDROXYBENZYLAMINE IN BEER

A simple method has been developed to allow the estimation of p-hydroxy-benzylamine in beer in the presence of other amines including tyramine. Analysis of commercial beers has shown a low and variable content. At the levels found, p-hydroxybenzylamine seems unlikely to be of physiological significance even when monoamine oxidase inhibitor drugs are being taken. The biosynthetic route for p-hydroxybenzylamine has not been identified but synthesis of the compound appears to be associated with the barley husk.     

VICINAL DIKETONES IN BEER. PART II: INFLUENCE OF SULPHUR DIOXIDE IN THE DETERMINATION OF DIACETYL IN BEER

The accuracy of the determination of diacetyl in beer using o-phenylenediamine is impaired by the presence of sulphur dioxide. This effect may be overcome when the distillate from the beer is collected in strongly acidic solution¹.     

WORT-BOILING IN RELATION TO BEER QUALITY

Comparisons of beers from worts mashed with pale ale malts (nitrogen 1·3%) at 150°F. (65·5°C.) and boiled for 1/2, 1 and 2 hr. show that increase in boiling time leads to slightly increased hop-utilization, decreased head-retention, improved non-biological stability and slight differences in flavour. Findings were very similar when the mashing temperature was either 145°F. (63°C.) or 155°F. (68°C.) except that, in the latter case, no difference in flavour was detectable between beers from long and short boiled worts. Stirring can replace vigorous boiling to secure normal hop-utilization and shelf-life but simmered worts give beers of characteristic flavour probably as a result of enhanced contents of hop oil. Use of a lightly kilned malt of high nitrogen content (1·8%) produced a characteristically different flavour from that obtained with pale-ale malt and reduced the utilization of hop substances by provoking a greater loss of this material during fermentation.