Ethanol In Beer Research Articles

Effects of β-Glucans and Environmental Factors on the Viscosities of Wort and Beer

This paper reports on the influence of molecular weight and concentration of barley β-glucans on the rheological properties of wort and beer. Environmental conditions such as pH, maltose level in wort, ethanol content of beer, shearing and shearing temperature were also examined for their effects on wort and beer viscosities. In the range of 50–1000 mg/L, β-glucans increased solution viscosity linearly with both molecular weights (MW) of 31, 137, 250, 327, and 443 kDa and concentration. The influence of MW on the intrinsic viscosity of β-glucans followed the Mark-Houwink relationship. Shearing wort and beer at approximately 13,000 s−1for 35 s was found to increase the wort viscosity but reduce beer viscosity. Shearing wort at 20°C influenced β-glucan viscosity more than shearing at 48°C and 76°C whereas the shearing temperature (0, 5 and 10°C) did not effect the viscosity of beer. At lower pHs, shearing was found to reduce the viscosity caused by β-glucans in wort but had no effect in beer. Higher concentrations of maltose in wort and ethanol in beer also increased the viscosity of β-glucan polymers. It was found that β-glucans had higher intrinsic viscosities in beer than in wort (5°C), and lower critical overlap concentrations (C*) in beer than in wort.

Graphite–Teflon composite bienzyme amperometric biosensors for monitoring of alcohols

Composite graphite–Teflon electrodes, in which the enzymes alcohol oxidase (AOD) and horseradish peroxidase (HRP), as well as the mediator ferrocene, are incorporated into the electrode matrix, are reported for the reliable monitoring of alcohols in food and beverages. The bienzyme electrodes are constructed by simple physical inclusion of the enzymes and the mediator in the bulk of graphite–70% Teflon rigid cylindrical pellets. The composite biosensors are robust and reusable because of the renewability of the electrode surface by polishing. Reproducible amperometric responses at 0.00 V were obtained with different electrodes constructed from the same pellet and from different pellets. No significant loss of the enzymes activities was found after at least 3 months of storage at 0 °C. The detection limits obtained by amperometry in stirred solutions can be advantageously compared with those achieved with commercial sensors for alcohols. The bienzyme electrodes are suitable to be used under flow-injection conditions, as well as for amperometric detection in HPLC. The bioelectrodes were employed for the determination of ethanol in beers, wines and liquors, using both batch- and flow-injection modes, and for the determination of methanol in wines and liquors by HPLC with amperometric detection. Only a dilution of the beverages was needed as sample treatment in all cases.

Genetic engineering of brewing yeast to reduce the content of ethanol in beer.

The GPD1 gene encoding the glycerol-3-phosphate dehydrogenase was overexpressed in an industrial lager brewing yeast (Saccharomyces cerevisiae ssp. carlsbergensis) to reduce the content of ethanol in beer. The amount of glycerol produced by the GPD1-overexpressing yeast in fermentation experiments simulating brewing conditions was increased 5.6 times and ethanol was decreased by 18% when compared to the wild-type. Overexpression of GPD1 does not affect the consumption of wort sugars. Only minor changes in the concentration of higher alcohols, esters and fatty acids could be observed in beer produced by the GPD1-overexpressing brewing yeast. However, the concentrations of several other by-products, particularly acetoin, diacetyl and acetaldehyde, were considerably increased.

Genetic engineering of brewing yeast to reduce the content of ethanol in beer

Genetic engineering of brewing yeast to reduce the content of ethanol in beer

Preprocessed barley, rye, and triticale as a feedstock for an integrated fuel ethanol-feedlot plant

Rye, triticale, and barley were evaluated as starch feedstock to replace wheat for ethanol production. Preprocessing of grain by abrasion on a Satake mill reduced fiber and increased starch concentrations in feedstock for fermentations. Higher concentrations of starch in flours from preprocessed cereal grains would increase plant throughput by 8-23% since more starch is processed in the same weight of feedstock. Increased concentrations of starch for fermentation resulted in higher concentrations of ethanol in beer. Energy requirements to produce one L of ethanol from preprocessed grains were reduced, the natural gas by 3.5-11.4%, whereas power consumption was reduced by 5.2-15.6%.

Determination of ethanol in beer by flow injection dual-pulse staircase voltammetric detection

Dual-pulse staircase voltammetry (DPSV), was studied for the determination of ethanol in beer using electrochemical detection and flow injection (FI). As the method did not require deaeration and had a sufficiently wide linear range to cover the area of application, it could be used for the direct determination of alcohol without any prior separation. Under the optimized conditions, in a 0.10 mol l–1 NaOH solution, the repeatability (relative standard deviation 1.9%, mean = 0.03 mol l–1 and n= 8), linear range (0.01–10 mol l–1) and detection limit (0.0006 mol l–1, 3s of the background current) of the developed method were found to be satisfactory for the determination of ethanol in beer samples by FI with a flow rate of 0.5 ml min–1, an injection volume of 100 µl and a maximum sample throughput of 60 samples per hour, prior to the overlapping of the FI peaks. No interfering effect was observed for additives at the concentrations commonly encountered in beer samples and the method was found to give similar results to the reference AOAC method. The method developed provides a general method for the electrochemical detection of alcohols and other organic compounds with alcoholic hydroxyl groups.

Biosensors for analysis of ethanol in food: effect of the pasting liquid

An amperometric biosensor for ethanol was constructed by using an alcohol dehydrogenase and NAD + modified carbon paste electrode. The sensor response to ethanol was studied using various pasting liquids. The electrode made with hexadecane as the pasting liquid showed an increase in sensitivity and linearity, compared to the one prepared with paraffin oil. This sensor was tested by assaying ethanol in beer and wine and the results compared favourably with spectrophotometric determinations.

Membrane inlet ion mobility spectrometry for on-line measurement of ethanol in beer and in yeast fermentation

A membrane inlet ion mobility spectrometric method was developed for on-line measurement of ethanol concentration in beer and in yeast fermentation. Main parts of the measurement system are an ion mobility spectrometer, M90, and a custom built membrane inlet. The M90 ion mobility spectrometer is unique in the sense that positive and negative ions are simultaneously measured at 6 different detection channels, 3 for positive ions and 3 for negative ions. The custom built membrane inlet utilized a microporous polypropylene membrane for sample introduction into the M90 instrument. The developed measurement system allowed analysis of ethanol at 0.05% ( v v ) levels, clearly sufficient for the applications reported here. Good signal linearity was observed at positive ion channels 1 and 3 in ethanol concentration range 0.2−10% ( v v ), calculated correlation coefficients were 0.989 and 0.999, respectively. Agreement between the ethanol concentration measured by membrane inlet ion mobility spectrometry and the values declared on the beer bottle labels was good. Reproducibility of signals of the detection channels which gave the best response for ethanol was excellent in ethanol concentration measurement of beer samples, coefficient of variation was 1% for all these channels. Membrane inlet ion mobility spectrometry was also shown to be capable of on-line ethanol measurement, confirmed by membrane inlet mass spectrometry, during yeast fermentations.

DETERMINATION OF ETHANOL IN BEER BY DIRECT INJECTION GAS CHROMATOGRAPHY: A COMPARISON OF SIX IDENTICAL SYSTEMS

Six identical gas chromatographic (GC) systems from the same manufacturer were evaluated for the determination of ethanol in beers. Each system was assessed for detector linearity and drift using standard ethanol solutions. Repeatability (r95) of each machine, repeatability (r95) of the GC method and reproducibility (R95) of the method over a range of ethanol concentrations (1–11% V/V) was determined using commercial beers. All six instruments were linear over the ethanol range 0–12% V/V and were in good agreement. Drift of the machines was negligible over the period of the analysis. Over the ethanol range 0.95 to 6.32% V/V the repeatability (r95) and reproducibility (R95) values were 0.050 and 0.083 respectively. Over the ethanol range 9.48 to 11.15% V/V the repeatability (r95) and reproducibility (R95) values were 0.153 and 0.227 respectively. Comparison of the precision values and those obtained in a recent IOB Analysis Committee Collaborative1 for the determination of ethanol by gas chromatography showed no significant differences between the two methods. The reported method is suitable for determination of ethanol in beers.

Stopped-flow near-infrared spectrometric determination of ethanol and maltose in beers

A near-infrared spectrometric procedure has been developed for the determination of ethanol in beer samples, based on the measurement of the ethanol absorbance maximum at 1693 nm above a base-line established between 1657 and 1720 nm, employing an 1 cm pathlength cell, and using a 4.5% (w/v) aqueous solution of maltose as a reference. For the analysis of real samples the method only requires a previous degassing of the samples, by filtration, and aqueous solutions of ethanol can be employed as standards. All types of beers, from regular beers containing about 5% (v/v) ethanol to low-alcohol beers with less than 1% (v/v) can be analyzed by using the same procedure. The method has a limit of detection of 0.07% (v/v) and a relative standard deviation of 0.2% for regular beer samples, and less than 2% for low-alcohol beer analysis. The use of the stopped-flow strategy provides a fast filling and cleaning of the measurement cells and a sample frequency of 120 injections per hour. Maltose can also be determined by additional measurement at ca. 1410 nm.

Derivative Fourier transform infrared spectrometric determination of ethanol in beers

A direct derivative Fourier transform infrared (FTIR) spectrometric procedure was developed for the determination of ethanol in beer samples. The method can be applied to the analysis of all types of beers, from regular to low-alcohol beers, and only requires a previous de-gassing of the samples as a preparation step. For the analysis of regular samples, with an alcohol content higher than 1% v/v, the method involves the use of the second-derivative FTIR measurements between the baseline, established from 1055 to 1037 cm–1, and the valley at 1046 cm–1 using a micro flow cell with ZnSe windows and a spacer of 0.029 mm after the accumulation of 10 scans. For the analysis of low-alcohol beers with less than 1% v/v of ethanol, the use of the first-derivative FTIR measurements, between the peak at 1052 cm–1 and the valley at 1040 cm–1, is more convenient than the use of the second-derivative measurements. However, in this instance the measurements must be corrected, taking into account the presence of maltose, which can be quantified by measuring the height between the peak at 1160 cm–1 and the valley at 1144 cm–1 in the first-derivative spectra. In the analysis of all types of beers, aqueous solutions of ethanol can be used as standards. The limit of detection of the proposed procedure is 0.025% v/v and typical relative standard deviations of 0.8 and 1% were obtained for five independent analyses of real samples containing 5 and 1% v/v of ethanol, respectively. The aforementioned procedures were applied to the analysis of real samples and the results obtained were coincident with those obtained by a reference method.

On-line determination of ethanol in bioprocesses based on sample extraction by continuous pervaporation

The development of a flow injection analysis system (FIA) based on immobilized enzymes for the on-line determination of ethanol in biological liquids is presented. The FIA system includes prior to enzymatic analysis a continuous purification by pervaporation, which is supplemented with an electronically controlled temperature device. Fundamental experiments with the pervaporation module as well as the application of this system for the monitoring of ethanol in beer and during a bakers' yeast cultivation (measurable range 1–100 mM) are presented. The results show good reproducibility and satisfactory agreement with those of a common enzymatic test kit. Incorporation of the pervaporation module enhanced the stability of the enzyme noticeably.

DETERMINATION OF ETHANOL IN BEER BY GAS CHROMATOGRAPHY (DIRECT INJECTION)-COLLABORATIVE TRIAL

A method employing gas chromatography for the determination of ethanol in beer has been collaboratively tested by the Analysis Committee of the Institute of Brewing. It was judged that precision values were independent of concentration over the range 0.93 to 6.05% V/V ethanol. Repeatability (r95) and reproducibility (R95) values of 0.061 and 0.136 respectively, were obtained over this range. At a mean level of 9.17% V/V, the r95 and R95 values were 0.154 and 0.284 respectively. This was probably due to dilution errors as the sample had to be diluted to bring it within the linear range of the method. A comparison of the precision values given by the gas chromatographic method, with those obtained in 1991/1992 by 8 laboratories in a major brewing company using 12 sample pairs, for the IOB Recommended Distillation Method, revealed that there is no significant difference between the precision data for the two methods.

Direct determination of ethanol in all types of alcoholic beverages by near-infrared derivative spectrometry

A rapid and accurate method has been developed for the direct determination of ethanol in all types of alcoholic beverages. The method, which does not require any sample treatment (except for simple de-gassing for beer samples or dilution with distilled water for spirits), is based on the use of the first derivative of the near-infrared absorbance spectrum. Measurements, carried out between the 1680 nm peak and the 1703 nm valley, provide a typical calibration graph [dA/dλ= 0.00002+ 0.0127 c(where c is the concentration of ethanol in % v/v)] for a concentration range up to 25% v/v with a regression coefficient of 0.999992 and a limit of detection (for k= 3) of 0.1% v/v. The interference of sugars in the determination of ethanol can be seen by the presence of bands in the derivative spectrum in the range between 1300 and 1800 nm and can be corrected. Results comparable to those found by a reference pycnometric procedure or by gas chromatography were obtained when the proposed method was applied to the determination of ethanol in beer, white and red wines, whisky, gin and rum samples and also in sweet wines and fruit liqueurs.

Enzymatic hydrolysis and fermentation of corn for fuel alcohol

The integration of enzyme saccharification with fermentation reduces the total time required to produce acceptable levels of ethanol. The use of a more concentrated mash (84.8 L total mash/bu corn) results in a 26.6% increase in ethanol productivity and a 21.4% increase in beer ethanol concentration compared to standard corn mash (96.6 L total mash/bu corn). Thus, the energy requirement and cost of distillation can be reduced. The addition of waste cola syrup at 30 g invert sugar/L total mash gave a 19% increase in ethanol concentration in the final beer and required only a small increase in the period of fermentation. Surplus laundry starch can replace 30-50% of the weight of corn normally used in fermentation without influencing ethanol production or the time required for fermentation. Both of these waste materials reduce the unit cost of ethanol and demonstrate the value of such substances in ethanol systems.

THE DETERMINATION OF ETHANOL IN BEER USING A BIOELECTROCHEMICAL CELL

A dye-linked alcohol dehydrogenase from Rhodopseudomonas acidophila, with a very high affinity for ethanol, has been incorporated into a bioelectrochemical cell and used for determining the concentration of ethanol in beer. The cell measures as little as 5–25 μg of ethanol, with a coefficient of variation of 3·1%. A wide range of beers and beer distillates have been used and the non-volatile components have been shown not to interfere with the assay. Other primary and secondary alcohols and aldehydes which are substrates for the enzyme do not contribute to the output of the cell at the concentrations in which they are normally encountered in beer. Values obtained using the cell correlate closely with those determined using a commercial test kit which incorporates a NAD-linked alcohol dehydrogenase, but results are obtained more rapidly and economically.

Malt Beverages and Brewing Materials: Gas Chromatographic Determination of Ethanol in Beer

Abstract The American Society of Brewing Chemists collaboratively tested a gas chromatographic method for determination of ethanol in beer. Ten laboratories collaborated in a comparison of the ASBC reference method for alcohol by distillation with the GC method. The latter was shown to be at least as precise as the former, it is more rapid, and it can be used for in-line or process monitoring. The method has been adopted official first action.

Determination of the substrates of dehydrogenases in biological material in flow-injection systems with electrocatalytic NADH oxidation

Flow-injection systems for the sensitive determination of dehydrogenase substrates are constructed by combining small columns of Eupergit-bound dehydrogenases with mediator-impregnated graphite electrodes as NADH sensors. Examples of applications given are the determination of d- and l-lactate in butter, l-glutamate in beef cubes, ethanol in beer, and the control of the enzymatic hydrolysis of N-acetyl- d, l-leucine by aminoacylase.

Determination of Glucose, Sucrose, Lactose, and Ethanol in Foods and Beverages, Using Immobilized Enzyme Electrodes

An enzyme electrode coupling immobilized oxidase enzymes with a hydrogen peroxide-sensitive electrode is described. An enzyme or enzymes are immobilized in a thin microporous membrane which fits directly over a platinum anode held at +0.700 V relative to a Ag/AgCl2 reference electrode. When an enzyme substrate diffuses into the membrane, hydrogen peroxide is produced. The hydrogen peroxide is then oxidized at the platinum anode, producing an electrical current that is directly proportional to hydrogen peroxide concentration, and hence substrate concentration. Glucose and sucrose in cereal samples, lactose in cheese, and ethanol in beer and wine were determined using enzyme electrodes. Relative precision of replicate analyses was better than +/- 2% and agreement with AOAC methods was good.

Biology of Ethanol-Producing Microorganisms

The production of ethanol by microorganisms as a result of the fermentation of substrates such as sugars or starch is a process that predates recorded history. The uses of ethanol can be divided into a number of categories: (1) potable ethanol in beer, wine, sake, cider, and perry, a variety of fermented fruit juices, and in distilled beverages such as whiskey, gin, vodka, brandy, rum, and liquors; (2) solvent ethanol in the laboratory, in pharmaceutical preparations such as tonics and cough syrups, as a solvent for hop constituents, and in cosmetics; (3) as a cosurfactant in oil-water microemulsions; (4) as an antiseptic and sterilant; and (5) as a fuel in automobiles either en its own or more usually admixed with gasoline. It should not be forgotten that by far the largest volume of ethanol produced via fermentation is employed for potable purposes. Consequently, brewing, viticulture, and enology and distilled beverages are biotechnological industries that make a significant contribution to the economy of most countries around the world.