Acids In Wort Research Articles

The Profiles of Low Molecular Nitrogen Compounds and Fatty Acids in Wort and Beer Obtained with the Addition of Quinoa (Chenopodium quinoa Willd.), Amaranth (Amaranthus cruentus L.) or Maltose Syrup.

Replacement of a part of malt with unmalted materials is a common practice in beer production. These materials may differ in chemical composition than barley malt, which in turn can contribute to changes in the final composition of the wort. Consequently, it may affect yeast metabolism and final parameters of the obtained products. In this research, two unmalted pseudocereals were used: quinoa (Chenopodium quinoa Willd.) and amaranth (Amaranthus cruentus L.). Maltose syrup was tested as a reference material due to its commercial usage as a substitute of malt in production of worts. Replacement of a part of the malt with quinoa or amaranth favorably influenced the profiles of amino and fatty acids. Due to the fact that the type and concentration of individual amino acids and fatty acids in the fermented wort significantly affect the flavor compounds synthesized by yeast, differences in the profiles of esters and higher alcohol have been noted in beers produced with pseudocereals.

Application of Plackett-Burman experimental design for investigating the effect of wort amino acids on flavour-active compounds production during lager yeast fermentation

Aroma-active higher alcohols and esters are produced intracellularly in the cytosol by fermenting lager yeast cells, which are of major industrial interest because they determine aroma and taste characteristics of the fermented beer. Wort amino acid composition and their utilization by yeast during brewer's wort fermentation influence both the yeast fermentation performance and the flavour profile of the finished product. To better understand the relationship between the yeast cell and wort amino acid composition, Plackett–Burman screening design was applied to measure the changes in nitrogen composition associated with yeast amino acids uptake and flavour formation during fermentation. Here, using an industrial lager brewing strain of Saccharomyces pastorianus, we investigated the effect of amino acid composition on the accumulation of higher alcohols and volatile esters. The objective of this study was to identify the significant amino acids involved in the flavour production during beer fermentation. Our results showed that even though different flavour substances were produced with different amino acid composition in the fermentation experiments, the discrepancies were not related to the total amount of amino acids in the synthetic medium. The most significant effect on higher alcohol production was exercised by the content of glutamic acid, aromatic amino acids and branch chain amino acids. Leucine, valine, glutamic acid, phenylalanine, serine and lysine were identified as important determinants for the formation of esters. The future applications of this information could drastically improve the current regime of selecting malt and adjunct or their formula with desired amino acids in wort. Copyright © 2017 The Institute of Brewing & Distilling

Selection of Protease for Increased Solubilization of Protein Derived Thiols during Mashing with Limited Release of Free Amino Acids in Beer

Extraction of protein-derived thiols by protease treatment during mashing for improvement of flavor stability in beer has previously been shown to cause concomitant increase in free amino acid concentrations and thereby increased levels of unwanted Maillard reaction products during aging. The previous methodology, with addition of protease dosed at 50 mg of enzyme/kg of malt at the beginning of the protein rest during mashing, resulted in increased amino acid concentrations of approximately 40% and increased free thiol concentrations of approximately 50% in wort compared with a control without protease addition. The objective of this study was to reduce the amount of amino acids in wort obtained by protease treatment but still obtain a significant increase in protein-derived thiols. In this paper we demonstrate that by omitting the protein rest during mashing in combination with addition of a protease with a higher temperature optimum dosed at only 3 mg of enzyme/kg of malt, it is possible to increase thiol concentrations in wort by 30% and with only a maximum 10% increase in amino acid concentration compared with a control. Pilot brewing showed that beer brewed with addition of protease resulted in a 30% increase in total thiol concentration, along with a decrease in or no effect on the concentration of some amino acids but also an increase in the concentration of other amino acids. Sulfite concentration was increased by 37%, so the effect of increasing free thiol concentration on flavor stability during storage could not be evaluated. Overall, similar brewing and sensory characteristics were obtained compared with a control beer brewed without addition of protease. Foam stability was decreased by protease treatment, and formation of haze was reduced by protease treatment.

Variability in the Release of Free and Bound Hydroxycinnamic Acids from Diverse Malted Barley (Hordeum vulgare L.) Cultivars during Wort Production

Volatile phenols have long been recognized as important flavor contributors to the aroma of various alcoholic beverages. The two main flavor-active volatile phenols in beer are 4-vinylguaiacol and 4-vinylphenol. They are the decarboxylation products of the precursors ferulic acid and p-coumaric acid, respectively, which are released during the brewing process, mainly from malt. In this study, the variability in the release of free and ester-bound hydroxycinnamic acids from nine malted barley ( Hordeum vulgare L.) varieties during wort production was investigated. A large variability between different barley malts and their corresponding worts was observed. Differences were also found between free ferulic acid levels from identical malt varieties originating from different malt houses. During mashing, free hydroxycinnamic acids in wort are both water-extracted and enzymatically released by cinnamoyl esterase activity. Esterase activities clearly differ between different barley malt varieties. Multiple linear regression analysis showed that the release of ferulic acid during mashing did not depend only on the barley malt esterase activity but also on the amount of ester-bound ferulic acid initially present in the wort and on its endoxylanase activity. The study demonstrates the importance of selecting a suitable malt variety as the first means of controlling the final volatile phenol levels in beer.

Determination of hydroxycinnamic acids and volatile phenols in wort and beer by isocratic high-performance liquid chromatography using electrochemical detection

The suitability of a simple and rapid isocratic RP–HPLC method with amperometric electrochemical detection for the simultaneous detection and quantification of hydroxycinnamic acids and their corresponding aroma-active volatile phenols in wort and beer is reported. The technique gives good specificity and sensitivity, and can therefore be used for routine monitoring of hydroxycinnamic acids in wort and the development of volatile phenolic flavour compounds during the beer production process and subsequent conservation.

Influence of the Brewing Process on Furfuryl Ethyl Ether Formation during Beer Aging

In beer, the development of a solvent-like stale flavor is associated with the formation of furfuryl ethyl ether. The synthesis rate of this important flavor compound is proportional to the concentration of furfuryl alcohol in beer. This study shows that furfuryl alcohol in beer is mainly formed by Maillard reactions initiated during wort boiling and malt production. A mechanism for its formation from alpha-(1,4)-oligoglucans and amino acids in wort and beer is proposed. During wort boiling, a quadratic relationship was found between the wort extract concentration, on the one hand, and the increase of furfuryl alcohol and furfural, on the other. The reduction of furfural by yeast during fermentation further increases the furfuryl alcohol content. In pale beers, the furfuryl alcohol concentration is essentially determined by the thermal load on wort during brewing operations. In dark beers, a considerable fraction of furfuryl alcohol may, however, come from the dark malts used. These results lead to important practical conclusions concerning the control over furfuryl ethyl ether in beer.

Determination of Free Phenolic Acids in Wort and Beer by Coulometric Array Detection

The simultaneous determination of 19 phenolic compounds was performed directly in wort and beer by a combination of reverse-phase high-performance liquid chromatography coupled with coulometric array detection. Chromatographic separation was achieved with an appropriate gradient of flow and a binary solvent based on phosphate buffer, methanol, and acetonitrile in a 45-min run. Eight serial coulometric detectors were used for on-line generation of voltammetric data to resolve coeluting compounds. The method was reliable and sensitive, the regression coefficient of standard calibration curves is 0.972 < or = r < or = 1.000, and the standard deviation value ranges from 0.010 to 0.129 mg/L for wort and from 0.002 to 0.332 mg/L for beer. The mean concentrations of phenolic acids were 22.1 and 33.8 mg/L, respectively, in worts and beers produced in Italy. These amounts represent 5 and 10% of the non-tannic, non-flavonoid phenols in wort and beer, respectively.

Determination of Free Fatty Acids in Wort and Beer

A method for quantitation of free fatty acids (FFAs) in beer and wort was developed. FFAs were extracted by a series of acidic chloroform/methanol and potassium hydroxide extractions. The esterification was performed by treating the extract with boron trifluoride/methanol. The FFA methyl esters thus formed were separated by gas-liquid chromatography and quantitated using three internal standards. The method was used to compare the FFA levels in clear (filtered) worts and trubcontaining worts, to determine the rate of FFA uptake by yeast during the initial stages of fermentation, and to determine the effect of storage and storage conditions on the FFA levels in finished beers.

Determination of Free Fatty Acids in Wort and Beer

Extraction des acides gras libres dans le mout et la biere. Les acides sont doses par CPG, apres derivatisation par le reactif BF 3 /methanol et par rapport a 3 etalons internes. Application au dosage dans les mouts clarifies ou non, a l'etude du metabolisme des levures et des effets de l'entreposage

Determination of Amino Acids in Wort and Beer by Reverse-Phase High-Performance Liquid Chromatography

An analysis of 19 amino acids in wort or beer was based on the precipitation of proteins followed by precolumn derivatization of the amino acids with o-phthaldialdehyde/2-mercaptoethanol. Amino aci...

Determination of Amino Acids in Wort and Beer by Reverse-Phase High-Performance Liquid Chromatography

An analysis of 19 amino acids in wort or beer was based on the precipitation of proteins followed by precolumn derivatization of the amino acids with o-phthaldialdehyde/2-mercaptoethanol. Amino acid separation was accomplished by means of a reverse-phase column. A detection limit at picomole level was reached through fluorescence. Variation coefficients for retention times and amino acid concentrations are reported. The results obtained by this method were evaluated in relation to those from a similar method where amino acid separation was accomplished by ion-exchange and postcolumn derivatization.

ESTIMATION OF FREE FATTY ACIDS (C8-C18) IN WORT AND BEER

A procedure is described for estimating the free fatty acids in wort and beer by gas liquid chromatography. The free fatty acids with carbon number 8 to 18 are estimated simultaneously from one injection, and by including two internal standards the reproducibility of the method is maintained over the whole range. It has been demonstrated that other lipid materials such as glycerides and esters of fatty acids do not interfere with the assay. Compared with other methods, this procedure is fairly rapid and is suitable for routine purposes. The reproducibility of the method has been assessed by analysing replicate samples of wort and beer and the precision in estimating individual fatty acids is given.

THE FATE OF AMINO ACIDS DURING MASHING AND HOP BOILING

In an infusion mash system the concentration of all α amino acids in sweet wort reaches a maximum value when approximately one-third of the total volume extracted has been run from the mashing vessel. The relative concentrations of each α amino acid in wort vary throughout the mash tun extraction owing to differences in rate of extraction of the amino acids and to the quantities produced by peptidase activity in the mash tun. The relative proportions of proline, alanine, glutamine and asparagine in the total α amino nitrogen content of wort decrease appreciably as the mashing process proceeds. Copper boiling results in the partial destruction of methionine, glutamic acid, lysine, arginine and valine present in sweet wort together with an increase in the concentration of ammonium ion in the wort.

The Quantitative Analysis of Amino Acids in Wort and Beer by Gas Chromatography

(1967). The Quantitative Analysis of Amino Acids in Wort and Beer by Gas Chromatography. Proceedings. Annual meeting - American Society of Brewing Chemists: Vol. 25, Proceedings of the Annual Meeting 1967, pp. 37-44.

The Adaptation of a Colorimetric Method to the Determination of Fatty Acids in Wort and Beer

(1965). The Adaptation of a Colorimetric Method to the Determination of Fatty Acids in Wort and Beer. Proceedings. Annual meeting - American Society of Brewing Chemists: Vol. 23, Proceedings of the Annual Meeting 1965, pp. 222-224.