Showing papers in "Journal of The Institute of Brewing in 1979"
TL;DR: The yeast plasma membrane regulates the movement of compounds into the yeast cell and of yeast metabolites from the cell into the medium, and the rate of penetration of organic acids into the fermentation cell depends on their lipophilic nature, and on their molecular size and degree of branching.
Abstract: The yeast plasma membrane regulates the movement of compounds into the yeast cell and of yeast metabolites from the cell into the medium. The rate of penetration of organic acids into the yeast cell depends on their lipophilic nature, and on their molecular size and degree of branching. During fermentation yeast synthesizes a vast number of aroma compounds. The numerically and quantitatively largest groups of aroma compounds include fusel alcohols, fatty acids and fatty acid esters. The yeast used and the fermentation conditions can influence the formation of aroma compounds. The yeast also has a profound effect on the formation of other aroma compounds, such as sulphur compounds and phenols. In addition to fermentation, the maturing of a beverage can also influence the aroma. During the maturing lactones, phenols and other compounds are extracted from the oak casks in which the beverage is aged. The presence of the so-called “whisky lactone”, β-methyl-γ-octalactone, is characteristic of a beverage that has been matured in oak.
148 citations
TL;DR: Joint Working Groups of the European Brewery Convention, the American Society of Brewing Chemists, and the Master Brewer's Association of the Americas have developed a system of flavour terminology to meet the dual needs of enabling brewers to communicate effectively about flavour and naming and defining each separately identifiable flavour note in beer as discussed by the authors.
Abstract: Joint Working Groups of the European Brewery Convention, the American Society of Brewing Chemists, and the Master Brewer's Association of the Americas have developed a system of flavour terminology to meet the dual needs of (i) enabling brewers to communicate effectively about flavour and (ii) naming and defining each separately identifiable flavour note in beer. The system comprises 44 terms to meet the first objective while 78 additional terms are suggested for the second. The Industry is urged to use this terminology and comment on it.
102 citations
TL;DR: An enzyme which catalyzes the release of soluble β-glucan from insoluble barley endosperm cell walls is described in this article, which increases in activity throughout malting.
Abstract: An enzyme is described which catalyzes the release of soluble β-glucan from insoluble barley endosperm cell walls. This enzyme increases in activity throughout malting. It has been partially purified and found to behave in the same way as an acidic carboxypeptidase on isoelectric focusing and in its sensitivity to inhibitors and activators and to heating. The importance of the β-glucan solubilizing enzyme in malting and mashing is discussed.
An improved method for β-glucan determination is described.
92 citations
TL;DR: Spheroplast fusion thus affords a means to genetically analyse brewing yeast strains, such an analysis having been difficult if not impossible by conventional hybridization techniques.
Abstract: Spheroplasts of brewing polyploid yeast strains have been successfully fused with spheroplasts of haploid yeast strains. After regeneration of the cell wall, stable fusion recombinants were isolated. Genetic analysis of these recombinants revealed that they contained the genotype of both parents, sporulated well with each ascus containing four spores and were indeed diploid. Spheroplast fusion thus affords a means to genetically analyse brewing yeast strains, such an analysis having been difficult if not impossible by conventional hybridization techniques.
66 citations
TL;DR: In this paper, the authors used four panels of assessors, using a flavour profiling system, to characterize the flavors of four beers using a set of adjectives, and found that training and experience improved reproducibility and discrimination without distorting the general pattern of flavour terms.
Abstract: The flavours of four beers were characterized by four panels of assessors, using a flavour profiling system. One panel carried out duplicate assessments. The results showed that training and experience improved reproducibility and discrimination, without distorting the general pattern of flavour terms reported. On the basis of the flavour profiles, the assessors could be divided into novices, those with some experience, and experts. Those novices likely to be good assessors could also be identified.
63 citations
TL;DR: The addition to wort of lipids derived from malt spent grains had a pronounced effect on yeast metabolism and the effect of the lipids on the synthesis of esters, fusel alcohols and medium chain fatty acids could be explained solely by their content of unsaturated fatty acids.
Abstract: The addition to wort of lipids derived from malt spent grains had a pronounced effect on yeast metabolism. The lipids allowed the fermentation of de-oxygenated wort and also stimulated yeast growth and the corresponding rate and extent of fermentation of air-saturated wort by yeast strains having a high oxygen requirement. The lipids increased the fusel alcohols content of beer and decreased the content of esters and medium chain-length fatty acids. The yeast incorporated sitosterol and unsaturated fatty acids from the spent grain lipids and the unsaturated fatty acids changed the pattern of fatty acids and sterols synthesized by the yeast. The fatty acids were present in the spent grain lipids mainly as triglycerides, free fatty acids and phospholipids. Using pure lipid compounds it was shown that the triglycerides were inactive and that the spent grain lipids exerted their effect on fermentation through the synergistic action of free unsaturated fatty acids, sitosterol and phospholipid. Phospholipid could be replaced by the detergent, Triton X-100. The effect of the lipids on the synthesis of esters, fusel alcohols and medium chain fatty acids could be explained solely by their content of unsaturated fatty acids.
61 citations
TL;DR: In this paper, large and small starch granules prepared from Proctor barley contain high levels of firmly bound protein and α-amylase under simulated mashing conditions is used to limit the rate of starch breakdown during mashing.
Abstract: Large and small starch granules prepared from Proctor barley contain high levels of firmly bound protein. Experiments with α-amylase under simulated mashing conditions suggest that this protein limits the rate of starch breakdown during mashing. Gel electrophoresis shows hordein to be a principal component. Treatment with cysteine or malt endopeptidase changes the nature of the associated protein.
58 citations
TL;DR: The elution patterns demonstrate that beer antigens, originating from barley or yeast macromolecules, can be separated from carbohydrates, from ‘proteose-like’ material and from each other in a few preparative chromatographic steps.
Abstract: The macromolecules of an antigen-rich beer fraction X were characterized by column chromatography. Elution profiles of protein, carbohydrate and immunochemically distinct antigens were recorded after separation on gels of Sephacryl, Sephadex, Sepharose, DEAE-Sephadex, SP-Sephadex, Bio-gel HT hydroxylapatite, Con A-Sepharose, and two types of antibody-Sepharose. The elution patterns demonstrate that beer antigens, originating from barley or yeast macromolecules, can be separated from carbohydrates, from ‘proteose-like’ material and from each other in a few preparative chromatographic steps. Affinity chromatography on a column of immobilized antibodies towards fraction X indicated that the antigenic material constitutes about 25% of the fraction. More than 20% of the protein in fraction X seems to originate from a distinct barley protein Z.
50 citations
TL;DR: In this paper, a method for the extraction and estimation of DMSO is described, and it is shown that reduction of the DMS produced during fermentation of ale and lager worts may explain the higher levels found in malts subjected to ale kilning schedules.
Abstract: Dimethyl sulphoxide (DMSO) is a normal component of malt and barley. A method is described for its extraction and estimation. DMSO is produced by the oxidation of dimethyl sulphide (DMS), particularly during kilning of malt, and higher levels are found in malts subjected to ale kilning schedules. DMS may also be oxidized during wort preparation.
DMSO can be reduced to DMS by yeast in glucose/salts medium, by yeast cell suspensions and by a cell-free extract. Reduction of DMSO is inhibited by methionine sulphoxide. The results suggest that reduction of DMSO may account for the DMS produced during fermentation of ale and lager worts.
50 citations
TL;DR: In this article, a flywheel connected to a microhammer mill is used to drive the hammers during milling, and a new apparatus for the rapid measurement of energy required to mill barley is described.
Abstract: A new apparatus for the rapid measurement of energy required to mill barley is described. This ‘Comparamill’ consists of a flywheel connected to a microhammer mill in such a way that the flywheel drives the hammers during milling, and several milling operations have been automated. When grain samples of currently used varieties grown in small field plots were compared, hot water extracts made of micromalted samples correlated (r = −0·59) with milling energy measurements on resting grains.
The results also demonstrate an environmental effect on malting performance and milling energy. Samples of certain varieties with unusual grain nitrogen contents did not malt in accordance with NIAB recommended list gradings. Furthermore samples of the variety, Mazurka grown in a particular environment were an exception to the correlation between milling energy and extract. This correlation improves (r = − 0·76) if all of the Mazurka samples are omitted.
50 citations
TL;DR: In this paper, a descriptive vocabulary of thirty-five terms was compiled for whisky, and odour, flavour and after-flavour were separately assessed on five-point scales, and two sets of flavour profiles of ten whiskies had been collected, during which they familiarized themselves with chemical standards used to define the descriptive terms.
Abstract: A descriptive vocabulary of thirty-five terms was compiled for whisky. Odour, flavour and after-flavour were separately assessed on five-point scales. After two sets of flavour profiles of ten whiskies had been collected, the assessors were given a period of training, during which they familiarized themselves with chemical standards used to define the descriptive terms. Finally, another two sets of profiles were collected. Training was found to improve reproducibility and discrimination. Odour or flavour descriptors alone were sufficient to distinguish between the whiskies, and the odour and flavour terms together provided little more information than the odour alone.
TL;DR: IsoHumulones undergo oxidative degradation in bottled beer during shelf storage to give volatile compounds including 2-alkanones with chain lengths of C3 to C11, alkanals with chain length of C2 to C10 2,alkenals of C4 to C7 or more and 2,4-alkadienals of c6 to C 7 as discussed by the authors.
Abstract: Isohumulones undergo oxidative degradation in bottled beer during shelf storage to give volatile compounds including 2-alkanones with chain lengths of C3 to C11, alkanals with chain lengths of C2 to C10 2-alkenals of C4 to C7 or more and 2,4-alkadienals of C6 to C7. Since some resultant aldehydes are involved in the formation of stale aldehydes, very high levels of isohumulones in beer may cause considerable staling of beer flavour.
Isohumulones were decomposed to these carbonyl compounds more easily than their derivatives, such as di- or tetrahydroisohumulones and humulinic acids, because the double bond or carbonyl group of the isohexenoyl side chain of the isohumulone molecule is involved in this degradation. This oxidation of isohumulones was greatly suppressed by addition of 300 ppm of sodium ascorbate or 40 ppm of ferrous ion.
TL;DR: In this paper, a universal standard substrate for the determination of malt endo-β-glucanase activity has been proposed, which is based on Bourne and Pierce's method.
Abstract: Various substrates for the determination of malt endo-β-glucanase activity have been tested in conjunction with the β-glucanase procedure advocated by Bourne and Pierce. It is recommended that one universal standard substrate should be used and that each determination should be measured against a standard check malt. Furthermore, great care must be exercised in the dissolution of the substrate to obtain consistent results.
TL;DR: In batch fermentations, carried out using a range of conditions, the specific rate of sugar utilization is shown to decline throughout, and the yields relating carbohydrate utilization to mass production remains approximately constant and the declining specific fermentation rate parallels declining specific growth rate.
Abstract: In batch fermentations, carried out using a range of conditions, the specific rate of sugar utilization is shown to decline throughout. When yeast mass is increasing, the yield coefficient relating carbohydrate utilization to mass production remains approximately constant and the declining specific fermentation rate parallels declining specific growth rate. When mass production ceases, maintenance of the yeast population requires only a low rate of sugar utilization. Attenuation associated with maintenance phase activity is relatively insignificant compared with that associated with growth.
TL;DR: In this article, the contents of dimethyl sulphide, dimethyl disulphide and dimethyl trisulphides have been determined in beers and wines by using a new sensitive method.
Abstract: By using a new sensitive method the contents of dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide have been determined in beers and wines, and the contents of these sulphides and diethyl sulphite measured in distilled beverages. The head-space volatiles are swept out from the beverage in a stream of nitrogen and adsorbed in a tube containing porous polymer. The volatiles are desorbed directly onto the column of a gas chromatograph by connecting the tube to the column and sliding the free end of the tube into the hot injection block from the oven side. The sulphur-sensitive flame photometric detector is used and the peak areas and identifications are collected on cassette and processed by computer to give the content of volatile sulphur compounds directly in μg/litre beverage. The detection limits are 2 μg/litre for dimethyl sulphide, 0.1 μg/litre for dimethyl disulphide and trisulphide, and 5 μg/litre for diethyl sulphite. The analysis time for each sample is 30 min and the coefficient of variation is 5%.
TL;DR: In this article, an infrared reflectance instrument has been calibrated against malt hot water extract (HWE) to estimate HWE on barley and that this might provide a suitable screening method for use in a breeding program.
Abstract: In recent years there has been an increasing awareness of the need for rapid screening tests for malting quality in barley. An infrared reflectance instrument has been calibrated against malt hot water extract (HWE). Results suggest that this type of instrument can be used to estimate HWE on barley and that this might provide a suitable screening method for use in a breeding programme.
Greater accuracy is achieved if separate calibrations are made for winter and spring barleys and the correlation coefficients with HWE were 0.70 (n = 168) and 0.82 (n = 134) respectively.
TL;DR: In this article, the application of principal components analysis to flavour characterization data has been examined by comparing and contrasting 32 beer samples, which comprised two samples of each of 16 brands of beer selected to represent four different types, contrasting ales and lager beers of two different strengths.
Abstract: The application of principal components analysis to flavour characterization data has been examined by comparing and contrasting 32 beer samples. These comprised two samples of each of 16 brands of beer selected to represent 4 different types, contrasting ales and lager beers of two different strengths. Two-dimensional plots of results using the first two principal components as axes showed resolution of the four groups of beers and the close proximity of the majority of the duplicate samples. Differences between samples thus revealed are in accordance with known differences between the beer flavours.
TL;DR: The half-life for the conversion of green malt dimethyl sulphide (DMS) precursor to free DMS has been determined at various temperatures and pH values as discussed by the authors, and the results of DMS analyses of samples taken during brewery trials are in reasonable agreement with the predicted values.
Abstract: The half-life for the conversion of malt dimethyl sulphide (DMS) precursor to free DMS has been determined at various temperatures and pH values. At pH 5·2 the half-life of the precursor in wort (S.G. 1·060) at its boiling point is 38 min, and is doubled for each 6°C fall in temperature. At pH 5·5 the half-life at the boiling point is 32·5 min.
Knowing the stability of the precursor at the various temperatures in the brewing process, the extent of conversion to free DMS in wort at pitching can be predicted for malt of a given precursor content and for a given set of process conditions. The results of DMS analyses of samples taken during brewery trials are in reasonable agreement with the predicted values. This work involved infusion mashing only, but the same principles apply to decoction mashing.
The fate of precursor and free DMS during fermentation and conditioning has been followed on a production scale. With some brews, where high levels of free DMS were present at pitching, much free DMS was lost during fermentation. Also, precursor DMS reappeared in the beer after a few days and there was some increase in the level of free DMS.
The DMS precursor in green malt has been isolated by ion-exchange and gel-filtration chromatography. A preparation has been obtained which has 0·6 mol potential DMS per mol amino nitrogen. Thin layer chromatography showed that the preparation and its hydrolysis product had the same Rf values as S-methylmethionine and homoserine respectively.
TL;DR: In this article, a series of rapid tests which have been proposed for the assessment of barley malting quality have been compared and the most accurate prediction of hot water extract was obtained by a multiple regression involving α-Amylase, Total Nitrogen and Grinding Resistance.
Abstract: A series of rapid tests which have been proposed for the assessment of barley malting quality have been compared. The most accurate prediction of hot water extract was obtained by a multiple regression involving α-Amylase, Total Nitrogen and Grinding Resistance.
TL;DR: Pilot scale brewing studies showed that dimethyl sulphide (DMS) can be produced during fermentation substantially in excess of that predicted by measurement of the DMS potential of the wort as mentioned in this paper.
Abstract: Pilot scale brewing studies showed that dimethyl sulphide (DMS) can be produced during fermentation substantially in excess of that predicted by measurement of the DMS potential of the wort. This occurred in low temperature fermentations conducted in conical vessels but not if open vessels were used. Neither the type of malt used nor the length of the wort boil substantially influenced the extent of this excess DMS production although they may have affected liberation from the yeast of unidentified material which released DMS on treatment with hot alkali.
It is suggested that yeast can synthesise S-methyl-L-methionine (SMM) and that metabolic breakdown of this compound was responsible for some of the DMS produced.
TL;DR: In this article, a rapid and quantitative method for measuring the content of trihydroxy octadecenoic acids in beer is described, which is extracted from degassed beer with ethyl acetate and methylated with diazomethane.
Abstract: A rapid and quantitative method for measuring the content of trihydroxyoctadecenoic acids in beer is described. The acids are extracted from degassed beer with ethyl acetate and methylated with diazomethane. After washing, the methylated compounds are silylated and analysed by gas chromatography. The coefficient of variation of the method is 3·2%. The amounts of total trihydroxyoctadecenoic acids in commercial beer samples varied from 4 to 12 mg/litre. The effects of these acids on beer flavour and head retention are discussed.
TL;DR: In this article, the breakdown of the malt-derived DMS precursor in boiling wort was found to be a first order reaction having a rate constant of about 0.02 min−1, implying a half life of about 35 min.
Abstract: In pilot brewing trials where wort boil time was varied from 15 min up to 2 hours the DMS contents of the resultant beers were greatly altered without substantial effect on many other aspects of beer quality. The worts were separately fermented by two yeast strains and a consistent difference between DMS levels of the pairs of beers was found which was almost independent of the boil time.
The breakdown of the malt-derived DMS precursor in boiling wort was found to be a first order reaction having a rate constant of about 0.02 min−1, implying a half life of about 35 min. The breakdown rate of S-methylmethionine in a boiling sucrose solution at pH 5.3 was similar. Free DMS was found to leave this wort substitute rapidly, again as a first order process, but with a rate constant of 0.18 min−1 (t1/2 ∼ 4 min) when the evaporation rate was 17%/h.
TL;DR: After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls as discussed by the authors, and apical abrasion was not essential to achieve this enhanced response.
Abstract: After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls. Apparently apical abrasion was not essential to achieve this enhanced response. The testae of treated grains appeared to be intact, and excluded externally applied gibberellic acid except at the base of the grains, where it normally gains entry. Essentially normal patterns of modification were observed in all grain samples, however treated. Tumbling and abrasion sometimes stimulate enzyme production in the absence of externally supplied gibberellic acid. It is deduced that these treatments do not alter the pattern of gibberellin penetration into grain.
Physical treatments cause limited embryo-damage and create fissures in and between the grain's surface layers. The treatments appear to exert their beneficial effects on enzyme production by allowing better access of oxygen in the air to the living grain tissues. Normally the oxygen supply limits enzyme formation. Surface populations of microbes sometimes limit oxygen levels in grain and repress enzyme formation.
TL;DR: In this paper, the Zeleny sedimentation test, developed to predict the bread-making quality of wheat flour, has been modified to predicting the malting potential of barley samples.
Abstract: The Zeleny sedimentation test, developed to predict the bread-making quality of wheat flour, has been modified to predict the malting potential of barley samples. The test appears promising for the evaluation of malting potential of unknown varieties.
TL;DR: The results demonstrated variation for these endosperm characters, with eighteen cultivars having a lower milling energy, and more than a hundred cultivars with a lower soluble β-glucan content than Gerkra, a barley with good malting quality as discussed by the authors.
Abstract: Estimates of grain hardness from measurements of milling energy were made on four hundred and eighty barley cultivars. The same cultivars were also subjected to an infra-red analysis used to predict soluble β-glucan and nitrogen contents.
The results demonstrated variation for these endosperm characters, with eighteen cultivars having a lower milling energy, and more than a hundred cultivars with a lower soluble β-glucan content than Gerkra, a barley with good malting quality. Of these, nine cultivars were lower for both characteristics. Information about this variation is, therefore, potentially useful when breeding for malting quality.
TL;DR: In this article, the heat-labile dimethyl sulphide (DMS) precursor in green malt has been isolated using ion exchange chromatography and gel-filtration under mild conditions.
Abstract: The heat-labile dimethyl sulphide (DMS) precursor in green malt has been isolated using ion exchange chromatography and gel-filtration under mild conditions. The final preparation had ∼0.7 mol potential DMS per mol amino groups. Thin layer chromatography of this preparation, and the gel-filtration behaviour of both crude and purified preparations, showed that the precursor had identical properties to S-methylmethionine (SMM).
The DMS precursor in a continental lager malt was also examined. The malt had been kilned under conditions which were expected to lead to a significant content of ‘active’ DMS precursor (reported to be metabolized to free DMS by suitable yeast strains, and contrasting with the ‘inactive’ green malt precursor). The DMS precursor in an extract of this kilned malt had the same elution volume on Sephadex G15 as SMM. There was no evidence for any difference from the DMS precursor in green malt. It is concluded that SMM is the only heat-labile DMS precursor in malt.
TL;DR: In this article, the influence of yeast strains and temperature conditions on the performance of Norwegian breweries was investigated. But the results showed that when the yeast strain was changed, the influence was dominated by the yeast and not the other factors.
Abstract: Laboratory and full scale fermentation experiments have been carried out in Norwegian breweries varying the yeast strains and temperature conditions.
Gas chromatographic data were submitted to factor analyses. One factor consisting of phenylethanol and the acetate esters was influenced by temperature. Another factor consisting of fatty acids or their derivatives is dependant on scale. When the yeast strain was changed the influence of the yeast tended to dominate the influence of the brewery.
TL;DR: In this article, a high-performance liquid chromatographic separation of hop resins on a commercially available microparticulate silica has been developed, which involves a new mechanism in hop resin separation.
Abstract: A high-performance liquid chromatographic separation of hop resins on a commercially available microparticulate silica has been developed. The chromatography involves a new mechanism in hop resin separation. A solvent containing di-n-butylammonium acetate is used. The method gives good separation of α-acid, iso-α-acid, β-acid and humulinic acid, and has been used for the quantitative analysis of α-acid and iso-α-acid in hop extracts and isomerised hop extracts.
TL;DR: With some malts, the readiness with which wort can be separated from a mash improves significantly over a period of about 20 days after kilning as discussed by the authors, which must be borne in mind when predicting mash-tun performance from laboratory results and also has a bearing on the decision to use very new malt in the brewery in times of high demand.
Abstract: With some malts, the readiness with which wort can be separated from a mash improves significantly over a period of about 20 days after kilning. This must be borne in mind when predicting mash-tun performance from laboratory results and also has a bearing on the decision to use very new malt in the brewery in times of high demand.
TL;DR: The results presented suggest that the use of a detection medium incorporating both glucose and maltose will result in increased ability to detect lactic acid bacteria.
Abstract: An examination of lactic acid bacteria involved in beer spoilage has demonstrated that many Pediococci and Lactobacilli are capable of growth on glucose media but incapable of growth on sucrose within 6 days. Some Lactobacilli are incapable of utilizing glucose for growth and are also unable to grow on media based on sucrose. All Lactobacilli studied which could not utilize glucose could utilize maltose. The results presented suggest that the use of a detection medium incorporating both glucose and maltose will result in increased ability to detect lactic acid bacteria.