Showing papers in "Journal of The Institute of Brewing in 1966"

The embryo of barley in relation to modification of the endosperm

Abstract: Differential dissection of the embryo of barley grains, followed by observation of the extent of modification and assessment of α-amylase production in the endosperm, has shown that the various organs of the embryo make the following different contributions to modification The isolated scutellum has a very limited ability to produce α-amylase and its powers of enzyme secretion are largely restricted to the peripheral region where aleurone cells are present The stimulus which initiates enzyme formation in the aleurone is largely derived from the nodal region of the embryo, especially from the base of the node where subsidiary rootlets are formed; the scutellum apparently lacks the means of producing this stimulus Translocation of the enzyme-inducing hormone from embryo to aleurone takes place through the apical half of the scutellum in which vascular tissue develops; this preferred route of translocation partially accounts for the asymmetric pattern of modification normally observed Removal of the first foliar leaf from within the coleoptile allows increased production of α-amylase in the endosperm: this leaf can be regarded as a natural consumer of gibberellin

Some effects of aeration on the growth and metabolism of saccharomyces cerevisiae in continuous culture

Abstract: In continuous fermentation of a complex, synthetic medium by Saccharomyces cerevisiae, a steady state was maintained for prolonged periods in the absence of oxygen. Growth reached a maximum at a low rate of aeration and under these conditions ester formation was markedly inhibited. At higher levels of aeration growth was reduced, the cells formed chains and aggregated, the rate of fermentation decreased and large quantities of acetoin and acetaldehyde were produced. Under fully aerobic conditions, ethanol production continued to account for the major part of the glucose consumed. The amount of diacetyl produced was insignificant at all rates of aeration. The extent of growth and the nitrogen content of the yeast were inversely related.

Wort‐boiling in relation to beer quality

Abstract: 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.

Changes in resin composition and brewing behaviour of hops during storage

Abstract: Changes in resin components and brewing value of several varieties of hops stored at two temperatures have been examined. Different varieties and temperatures of storage gave rise to significant changes in resin and oil composition, but these variables had little effect on bittering capacity.

Some factors affecting the concentration of diacetyl in beer

Abstract: Investigations of factors affecting the production of diacetyl during fermentation have shown large differences in the abilities of different strains of brewer's yeast to produce diacetyl. Studies on pilot scale and on small laboratory fermentations have established a connection between the concentration of amino acids in the wort and that of diacetyl in the fully fermented beer. Control of the ratio of amino acids to sugars in wort is thus an important factor in maintaining concentrations of diacetyl in beer at an acceptable level. The effects of increased pitching rate and of high-temperature fermentation in enhancing the production of diacetyl are demonstrated.

The influence of temperature on some properties of yeast

Abstract: The effects of temperature on the growth of yeast and on its metabolic activity in distiller's malt wort have been studied. In un-aerated fermentations, maximum yeast production takes place at about 30° C. whereas the growth rate in aerated cultures is highest at 35° C. The lag phase of the yeast studied fell from 6 hr. at 20° C. to 2·8 hr. at 25° C. and was not thereafter greatly affected by increases of temperature until 42° C. was reached, at which point growth ceased. Maltase activity was maximal at 25° C. when considered in terms of unit quantities of either yeast or fermenting wort, but the optimum temperature for initial fermentation velocity varied according to the time over which the measurement was made, being maximal at 40° C. for 0·5 hr., and at 35° C. for 2 hr. Alcohol production was highest at 25° C. whereas glycerol and higher alcohol formation took place optimally at 30° C.

The aroma components produced by yeast in nitrogen-free sugar solution

Abstract: In nitrogen-free sugar fermentation yeast produces several other volatile compounds in addition to ethanol. Most of these compounds are distilled over with the ethanol. When the aroma components obtained from the ethanol fraction of a nitrogen-free sugar fermentation were compared with the aroma components of whisky, they showed a qualitatively striking similarity. There was a clear difference in the proportions of the components, however, a fact for which the distillation procedure might be at least partly responsible. The distillate obtained from the fermented sugar solution contained iso-amyl alcohol and β-phenethyl alcohol as well as the ethyl esters of caproic, caprylic, capric, lauric and palmitic acids in considerable amounts. The same acids also appeared as main components among the free acids and, further, isobutyric and isovaleric acid were found quite abundantly. The similarity between the aroma compounds formed in nitrogen-free sugar fermentation and the aroma fraction of alcoholic beverages indicates that the yeast is responsible for the bulk of the aroma compounds produced.

Studies on carbohydrate-metabolizing enzymes. part xiv. the specificity of r-enzyme from malted barley*

Abstract: R-Enzyme and limit dextrinase of malted barley have been separated by continuous electrophoresis. The preparation of R-enzyme, which was free of α-amylase, hydrolysed the outermost inter-chain linkages of amylopectin and glycogen which had interior chain lengths exceeding five glucose residues. It had no action on glycogen with shorter interior chains, on pullulan, or on oligosaccharides containing α-1, 6-glucosidic linkages.

Serological studies on brewing yeasts

Abstract: In a serological investigation of twelve strains of Saccharomyces carlsbergensis, three strains were found to be antigenically different from the other nine, but no physiological or morphological properties characterized either type. S. rouxii, although antigenically very similar to S. carlsbergensis, was found to be sufficiently different to allow serological differentiation. A preparation is described of a serum which agglutinates three of the twelve S. carlsbergensis strains tested, but not organisms of ten other Saccharomyces spp., including S. cerevisiae, S. ellipsoideus, S. diastaticus and S. rouxii. S. ellipsoideus, S. diastaticus and the remaining strains of S. carlsbergensis were found to be serologically identical and could only be distinguished by fermentation of melibiose and starch.

The influence of oxygen on the production of diacetyl during fermentation and conditioning

Abstract: Although varying concentrations of oxygen in wort at pitching do not affect the production of diacetyl, its availability during fermentation has a significant effect The enhanced production of diacetyl resulting from access of oxygen during fermentation is caused by its effect in increasing yeast growth and in altering the balance of amino acids relative to sugars and not by a direct oxidation of acetoin Oxygen has no effect upon the concentration of diacetyl during storage and conditioning, provided that the beer is free from contamination

Simultaneous assessment of changes occurring during batch fermentation

Abstract: Detailed study of the fermentation of wort by Saccheromyces cerevisiae on a pilot scale showed that all the oxygen and considerable quantities of certain amino acids present in the wort were absorbed by the yeast before active fermentation commenced. The pH fell rapidly after pitching and reached a constant level after 32 hr. The α acids and iso α acids in the wort diminished in parallel with the decrease in pH and the increase in concentration of suspended yeast, respectively. Esters and higher alcohols appeared as the carbohydrate content of the wort diminished. Their production did not parallel the uptake of amino acids or changes in the amount of suspended yeast. The level of diacetyl reached a maximum when valine was fully taken up from the wort. Distillation of fermenting wort caused production of diacetyl.

Phenolic components of brewing materials and their relation to non-biological hazes

Abstract: Extraction of phenolic materials from the grist during mashing and the subsequent fate of phenolic compounds in the various brewing procedures has been followed quantitatively by utilizing their reaction with diazotized p-amino benzoic acid to yield coloured products. A semi-automatic procedure has been developed. The extraction pattern for phenolic compounds from the grist resembled that found for sugars but the extraction maximum occurred earlier. In the strong worts, much of the phenolic material was either polymerized or bound to protein, but in the weak worts most of the phenol present was dialysable. An examination of the worts has been made using gel-filtration on columns of cross-linked dextran.

The determination of beer components by gas‐liquid chromatography

Abstract: A procedure is presented for the routine analysis of organic beer components. Beer is extracted with carbon disulphide to yield a concentrate which is submitted to a single quantitative dual-column gas chromatographic analysis. A satisfactory overall order of reproducibility, sensitivity and speed is achieved under the conditions described. At least 15 clearly-resolved peaks are obtained representing alcohols, esters and acids. The method is illustrated by the determination of capric acid, caprylic acid and β-phenylethanol in eight commercial bottled lagers.

Further studies on the foam‐stabilizing substances in beer

Abstract: A material containing both carbohydrate and protein together with some ferulic acid, and which has pronounced foam-stabilizing activity, has been isolated from beer. A fraction similar in constitution and activity to the beer constituent has been recovered from an aqueous extract of barley flour. These materials are comparable with a glycoprotein present in wheat flour; the latter has been shown to be effective in the stabilization of beer foam. There was little difference in the amount and activity of extracts prepared from different varieties of barley.

Further studies on the oxidation of hop resins

Abstract: The autoxidation of humulone, isohumulone, colupulone and cohulupone has been studied using chromatography on an ion-exchange resin. Humulone gave a mixture of products which were largely insoluble in light petroleum whereas most of the products obtained by autoxidation of colupulone were soluble in that solvent. Cohulupone was isolated for the first time from the autoxidation of colupulone. The brewing value of a water-soluble fraction of hops was also examined. The degree of resolution obtained from the ion-exchange chromatographic system enabled a detailed examination of the constituents of hop concentrates and extracts to be made.

Gas chromatographic determination of tyrosol and tryptophol in wines and beers

Abstract: A gas chromatographic method for the determination of tyrosol and tryptophol in wines and beers has been developed. The aromatic fusel alcohols are extracted with ether or ethyl acetate from a sample made alkaline with Na2CO3 and saturated with NaCl. In beer determinations the extraction is performed with ethyl acetate in order to avoid complications caused by emulsion. Most of the solvent is removed by distillation and the rest is cautiously allowed to evaporate. The gas chromatographic determination of tyrosol and tryptophol is performed in a 0·5-m. Apiezon M-DEGS column at 190°C. According to the infra-red spectra, both components are eluted without being decomposed at this temperature. In the grape wines investigated, tyrosol was found in amounts of 10–40 mg. per litre, in two Finnish berry wines 10–15 mg. per litre and in two different types of pale lager beers 5–10 mg. per litre. The same samples contained about 1–4 mg. tryptophol per litre. The two white grape wines and one red berry wine were exceptional, with only 0·2–0·3 mg. tryptophol per litre.

The embryo as an activator of gibberellic acid induced α - amylase

Abstract: Evidence is presented which suggests that, in addition to gibberellic acid, a second factor produced by the embryo is involved in the formation of α-amylase by the aleurone of intact barley grains.

Formation of esters from lower fatty acids by various yeast species

Abstract: A study has been made of the total formation of volatile esters and of the formation of ethyl esters from butyric acid, valeric acid, isocaproic acid and caproic acid in fermentation with a number of yeast species of various genera. The distribution between the esters studied was essentially the same for all the yeast species tested although the quantitative results differed considerably. There was no correlation between the total formation of volatile esters and the formation of esters from acids added to the medium.

The influence of the method of preparation of pitching yeast on its production of diacetyl and acetoin during fermentation

Abstract: Yeasts propagated under different conditions have been tested for their ability to produce diacetyl and acetoin during fermentation of wort. It has been shown that the method of preparation of the pitching yeast can have a considerable influence on the production of these fermentation by-products and that different yeast strains respond differently in this respect.

Use of formaldehyde for the reduction of the anthocyanogen content of wort

Abstract: Reduction in wort anthocyanogen content is achieved effectively when formaldehyde is introduced to the mash at the beginning of the mashing operation. Concentrations of 50 p.p.m. of formaldehyde with respect to the malt (equivalent to about 5 p.p.m. with respect to the final wort volume) are effective in reducing the anthocyanogen content by about 30%. Treatments four times as strong reduce the anthocyanogen content by 60–70%, and the effect is accompanied by a fall of up to 10% in the soluble nitrogen content of the wort. It seems likely that a condensation reaction occurs between anthocyanogens and a nitrogenous fraction of the wort. Under the conditions quoted, formaldehyde residues in the finished beers are less than 0·2 p.p.m. and are no greater than those observed in corresponding untreated control beers. Beers produced from treated mashes exhibit great non-biological stability, but are quite normal in other respects. The effect of formaldehyde on the anthocyanogen contents of worts and beers is of substantial theoretical interest and it is probable that it will also have a commercial application.

Determination of some lipid constituents of baker's yeast

Abstract: Lipid was extracted from whole yeast cells with difficulty because of the limited porosity of the cell wall and its sensitivity to dehydrating solvents. Extraction from mechanically broken cells was rapid and complete. Metabolic alteration of lipid when cells were disintegrated was minimized by first heating a yeast suspension briefly at 90°C. Details are given for the routine analysis of yeast phospholipids by quantitative paper chromatography and of neutral lipids by column chromatography. Lysophosphatides were found in some types of yeast after drying, but not in pressed commercial yeast or in yeast grown on synthetic media. They were formed when yeast was suspended in methanol-water, as yeast phospholipase A was activated and split palmitoleic acid from lecithin and phosphatidyl ethanolamine. Phosphatidyl inositol in baker's yeast contained a higher proportion of saturated fatty acids than other phospholipids. Sterols were present free and as esters with palmitoleic and oleic acids. Phospholipid content was affected by growth conditions. A high level of inositol in the growth medium reduced the formation of neutral lipid but did not affect the content of yeast phospholipid.

Formation of n‐propyl alcohol by cell‐free extracts of saccharomyces cerevisiae*

Abstract: n-Propyl alcohol formation from α-ketobutyric acid was obtained in cell-free extracts of Saccharomyces cerevisiae var. ellipsoideus and the optimal conditions for the formation were determined. In the presence of NAD† the concentration of n-propyl alcohol formed was the same with extracts of yeast grown either aerobically or anaerobically, but in the presence of NADP more n-propyl alcohol was formed with extracts of aerobic yeast. There was no evidence for an increase in an NADP-specific alcohol dehydrogenase, and the increased formation of n-propyl alcohol by extracts of aerobic yeast with added NADP was attributed to a greater reductive capacity of the extracts of aerobic cells in the presence of NADP. No system of enzymes for the formation of n-propyl alcohol was found other than those involved in ethyl alcohol formation. However, alcohol dehydrogenase from aerobic cells had a greater specificity for n-propyl alcohol, compared with ethyl alcohol, than the enzyme from anaerobically grown cells. This difference may be part of the explanation for greater n-propyl alcohol formation in aerobic cultures.

Water uptake and enzymic activity during steeping of barley

Abstract: During steeping of barley, the increase in moisture content of the grain exhibits two phases, of duration respectively 6–10 hr. and 35–50 hr. In the first phase, the embryo absorbs water preferentially with the endosperm imbibing less quickly. In the second each part absorbs slowly. In the first phase, amylase, ribonuclease and phosphatase activities of the embryo all rise appreciably, paralleling water uptake, but after about the first 6 hr. all fall and only rise again if the steep liquor is changed or if the grain is exposed to the atmosphere. There is no fall in activity if the liquor is drained after 6 hr. Enzyme activities in the endosperm show no appreciable rise until after 4 hr. steeping. In the second place, activity of the whole grain and of the individual parts bears no relation to water uptake. Gibberellic acid stimulates enzymic activity in both embryo and endosperm at very early stages. The importance of these findings in regard to multiple steeping processes is discussed.

Some observations on commercial malt extracts

Abstract: The historical development of malt extracts is reviewed. Analyses are given of physical properties, such as density and viscosity, and the inter-relationships of these properties are discussed. Chemical composition of malt extracts is related to enzymic properties, and some factors which affect the keeping qualities of malt extracts are examined.

European brewery convention tests of the e.b.c. colour discs for wort and beer

Abstract: The introduction of the EBC Colour Scale in 1951 considerably reduced the wide discrepancies in beer colour measurement given by the earlier Brand and Iodine Scales The present situation is reviewed here with the object of further improvement Reasons are given for preferring eye to instrumental measurement of wort and beer colour In a collaborative study of the EBC glasses, Hartong solution has been used as a standard, reproducible colour solution with an absorption curve similar to that of beer These tests have given similar average results for the solution in all laboratories and values have not been significantly affected by surrounding lighting conditions or by the use of any one of the three varieties of EBC glasses which exist Differences in readings between observers have been shown to exist and methods are given for reducing personal variation Methods for the routine control and maintenance of the EBC glasses and comparators are given A definition of the EBC Scale is given in chromaticity co-ordinates

Gas‐liquid chromatography of wort and beer carbohydrates i. the characterization of wort, beer, and brewing syrup carbohydrates

Abstract: Gas-liquid chromatography has been applied to the separation of the trimethylsilyl derivatives of wort, beer and corn syrup carbohydrates. The major carbohydrates identified in worts, beers, and corn syrups include fructose, glucose, sucrose, maltose, isomaltose, maltotriose and maltotetraose.

The use of acetic acid and sulphur dioxide to limit malting losses

Abstract: The effects of spraying acetic acid or solutions of sulphur dioxide and of steeping in solutions of acetic acid have been investigated in micromalting trials. Spraying germinating grain with acid solutions on the fourth day of germination significantly increased both hot and cold water extracts and total soluble nitrogen, while reducing rootlet growth and total malting loss. The percentage fermentability of wort derived from malt sprayed with a solution of acetic acid was less than that of controls and had a lower pH. Malt prepared from grain steeped in dilute acetic acid and sprayed with gibberellic acid on casting was ready for kilning in a shorter time with smaller malting loss and rootlet production, but with an elevated hot water extract, percentage fermentability and soluble nitrogen content. On this basis of the original dry weight of barley, increases in the yield of extract of the order of 5% over that obtained from control malts have been achieved.

Gas chromatographic studies on volatile alcohols and esters of beer

Abstract: A method is presented for concentrating volatile alcohols and esters from beer by distillation, and analysing six alcohols and ten esters in the distillate simultaneously by gas chromatography. Using this method, the composition of volatile alcohols and esters in different types of beer was analysed and the characteristic patterns of aroma of these beers were demonstrated. Further, the formation of the volatile fraction during fermentation was investigated and it was concluded that the formation of volatile alcohols is completed by the end of the primary fermentation period and does not occur in the lagering tank. On the other hand, ester formation continues from the middle stage of primary fermentation to the initial stage of after-fermentation.