Microbial acidification,alcoholization, and aroma production during spontaneous lambic beer production

Acidic beers, such as Belgian lambic beers and American and other coolship ales, are becoming increasingly popular worldwide thanks to their refreshing acidity and fruity notes. The traditional fermentation used to produce them does not apply pure yeast cultures but relies on spontaneous, environmental inoculation. The fermentation and maturation process is carried out in wooden barrels and can take up to three years. It is characterized by different microbial species belonging to the enterobacteria, acetic acid bacteria, lactic acid bacteria, and yeasts. This review provides an introduction to the technology and four fermentation strategies of beer production, followed by the microbiology of acidic beer production, focusing on the main microorganisms present during the long process used for the production of Belgian lambic beers. © 2018 Society of Chemical Industry     

The Release of Ferulic Acid and Feruloylated Oligosaccharides During Wort and Beer Production

Ferulic acid, a very attractive natural antioxidant is present in beer in free form, but the main form is the bound form as feruloylated oligosaccharides. Previous research showed that feruloylated oligosaccharides more effectively inhibited lipid and Low Density Lipoprotein oxidation than free ferulic acid. The aim of the present study was to evaluate free and bound ferulic acid concentrations throughout the brewing process in experimental mashes (worts, beers during fermentation, maturation and storage), and to conduct a comparison in commercial beers. Another aim of the study was to investigate methods to increase levels of bound ferulic acid in beer due to the potential health benefits. Specifically, the influence of commercial enzyme preparations on both forms of ferulic acid contents was studied. Five commercial enzyme preparations during mashing were examined: Celluclast, Shearzyme, Viscozyme, Cereflo and Ultraflo. In all experimental beers, the concentrations of esterified ferulic acid were 4–6 fold higher than the corresponding free ferulic acid contents, depending on the enzyme preparation used. Ferulic acid contents in the ester form in experimental beers were in the range of 748.4 mg/hL to 1244.3 mg/hL, whereas the contents of free ferulic acid were in the range of 134.6 mg/hL to 275.2 mg/hL. Comparison of free and bound ferulic acid contents in experimental beers, produced using enzyme preparations and commercial beers found in a local market, showed that concentrations of bound ferulic acid in experimental beers were significantly higher than in commercial beers, whereas concentrations of free ferulic acid in experimental and commercial beers were comparable.     

比利时/德国小麦啤酒风味物质差异研究

以大麦芽、小麦芽和未发芽的小麦为原料,添加酒花、橘皮和芫荽籽,使用上面发酵酵母No.303,酿造比利时风格和德国风格小麦啤酒。该研究介绍了两种风格小麦啤酒的酿造工艺,对两种风格的成品小麦啤酒进行风味物质检测分析以及感官品评,探讨了比利时风格小麦啤酒和德国风格小麦啤酒风味物质的差异。结果表明,比利时风格小麦啤酒乙醛含量更为适宜（约为2.6 mg/L）,高级醇和乙酸含量较高（分别为113 mg/L和160 mg/L）,酯类物质含量偏低（约为50 mg/L）,成品啤酒橘香味突出,但酯香味不够充足;德国风格小麦啤酒乙醛和酯类物质含量略高（分别为3 mg/L和63 mg/L）,高级醇含量稍低（约为104 mg/L）,乙酸含量适宜（约为135 mg/L）。     

Development of a quantitative method for organic acid in wine and beer using high performance liquid chromatography

This study was conducted to compare the organic acid content in liquors (red wine, white wine, and beer) using three different high-performance liquid chromatography analysis methods. Post-column reaction methods (method 2 and 3) were found to be more promising than UV-detection method (method 1). Using method 2 (two columns), the analyzed red wine was found to contain 2,652.4 mg/L tartaric acid and 1,392.9 mg/L lactic acid but relatively lower amounts of malic acid (271.0 mg/L). Furthermore, tartaric acid (1,160.8–2,749.1 mg/L) and malic acid (470.2–3,107.9 mg/L) were the major components in white wine. Beers were analyzed using method 3 (one column). In the analyzed foreign beers, lactic acid (95.9–226.4 mg/L), malic acid (62.2–110.5 mg/L), acetic acid (93.5–183.8 mg/L), and succinic acid (37.0–56.2 mg/L) were detected. Similar to the foreign beers, the contents of succinic acid in the domestic beers were the lowest. The proposed methods could be useful for quantitative analysis of organic acids in wine and beer.     

Differences in protein content and foaming properties of cloudy beers based on wheat malt content

To investigate differences in protein content, all barley malt beer, wheat/barley malt beer and all wheat malt beer were brewed, and the protein during mashing, wort, fermentation and beer determined. It was shown that protein was mainly extracted during mashing and the protein rest phase, decreased in the early stages of fermentation and remained almost steady during wort boiling and cooling, in the middle and late stages of fermentation. By separating beer foam from beer, similar protein bands of 51.7, 40.0, 27.3, 14.8, 6.5 and < 6.5 kDa appeared in the three beers, defoamed beers and beer foams using the sodium dodecyl sulphate polyacrylamide gel electrophoresis. Quantitatively, protein bands of 6.5–14.8 and <6.5 kDa had the highest contents in the three beers. Unique bands at 34, 29.2, 23.0, 19.7 and 17.7 kDa were found in beer, defoamed beer and beer foam from wheat beer and all‐wheat malt beer, respectively. Wheat beer foam showed the best foam stability and the protein in all barley malt beer showed the best migration to the foam. The beer foam properties were influenced by not only protein content but also protein characteristics and/or origin. It is suggested that the barley malt contributed the beer foam ‘skeleton protein’ while protein components from wheat malt kept the foam stable. © 2018 The Institute of Brewing & Distilling     

三种不同酵母对啤酒发酵及风味的影响

本实验采用Y1110、安琪、模式三种不同的啤酒酵母,在同种工艺条件下测定发酵过程中α-氨基氮(α-AN)、pH、双乙酰、高级醇等指标,并比较三种不同啤酒的风味物质含量。结果表明:Y1110增殖最快,α-AN和pH值下降最快,双乙酰还原较快,后酵结束双乙酰含量最低,啤酒样品含醇量较高,适于醇厚型啤酒酿造;安琪酵母增殖最慢,α-AN和pH值下降最慢,啤酒样品含酯量较高,适于淡爽型啤酒酿造;模式酵母酯类与醇类含量都很高,不适于实际生产。     

啤酒酿造中二甲基硫、甲基蛋氨酸、二甲基亚砜含量的变化与控制

为控制啤酒风味物质二甲基硫（dimethyl sulfide,DMS）的含量,实验运用气相色谱-氢火焰离子化检测器测定了15 种国内市售啤酒样品DMS的含量,并研究了啤酒酿造中DMS、甲基蛋氨酸（S-methylmethionine,SMM）、二甲基亚砜（dimethyl sulfoxide,DMSO）的含量变化。结果表明,抽取的国内市售啤酒样品中有47%的样品DMS含量超出60 μg/kg,特别是爱尔啤酒（Ale）中71%的样品DMS含量超出60 μg/kg,最高值达到105 μg/kg;实验抽检10 种国内市售麦芽DMS、SMM、DMSO含量,不同麦芽间DMS与二甲基硫前驱体（dimethyl sulfide precursor,DMSP）差异较大,差异最高达160%,且多数小麦芽的DMS与DMSP含量低于澳麦芽。实验研究了麦汁煮沸、发酵过程中的DMS及DMSP含量的变化,在100 ℃、pH 5.6时,麦汁煮沸40 min后DMS含量比初始含量降低92%,SMM的半衰期为31 min。发酵过程中DMS含量在发酵旺盛期时有明显的下降,最高下降41%。     

Predicting acetic acid content in the final beer using neural networks and support vector machine

Most acetic acid found in beer is produced by yeast during fermentation. It contributes significantly to beer taste, especially when its content is higher than the taste threshold in beer. Therefore, the control of its content is very important to maintain consistent beer quality. In this study, artificial neural networks and support vector machine (SVM) were applied to predict acetic acid content at the end of a commercial‐scale beer fermentation. Relationships between beer fermentation process parameters and the acetic acid level in the fermented wort (beer) were modelled by partial least squares (PLS) regression, back‐propagation neural network (BP‐NN), radial basis function neural network (RBF‐NN) and least squares‐support vector machine (LS‐SVM). The data used in this study were collected from 146 production batches of the same beer brand. For predicting acetic acid content, LS‐SVM and RBF‐NN were found to be better than BP‐NN and PLS. For the comparison of RBF‐NN and LS‐SVM, RBF‐NN had a better reliability of model, but lower reliability of prediction. SVM had better generalization, but lower reliability of model. In summary, LS‐SVM was better than RBF‐NN modelling for the prediction of acetic acid content during the commercial beer fermentation in this study. Copyright © 2013 The Institute of Brewing & Distilling     

Development of low-alcohol isotonic beer by interrupted fermentation

Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L⁻¹), osmolality (mOsmol kg⁻¹), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L⁻¹ gallic acid), reducing and total sugars (%) and Na and K contents (mg L⁻¹). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.     

降低啤酒中乙酸含量的初步研究

啤酒中的乙酸主要来自麦芽及发酵过程。不同品种和制麦工艺制作的原料麦芽中乙酸含量有较大差异。麦汁浓度与麦汁pH值的升高均使乙酸增加，尤以后者的影响更显著。发酵前期，乙酸含量不断减少，在后酵过程中到达最低值后缓慢上升，最后趋于稳定。另外，在保证煮沸麦汁质量的前提下，增加煮沸时间和强度能大量减少乙酸含量。空气洗涤处理对麦汁中乙酸量的降低也有明显影响。     

国内啤酒有机酸组成及其综合评价

有机酸是对啤酒质量(口感和稳定性)有重要影响的一类物质,本文通过采用HPLC法测定国内市售的20种啤酒中主要有机酸的含量,且采用统计学中多指标综合评价法,建立了以6种有机酸(丙酮酸、苹果酸、乳酸、乙酸、柠檬酸和琥珀酸)为指标综合评价啤酒的方法。通过该方法可以对啤酒或者试验样品进行整体性比较和“优劣”排序,对研究啤酒中有机酸类物质的组成有重要意义。     

Genetic and physiological characterization of yeast isolated from ripe fruit and analysis of fermentation and brewing potential

‘Wild’ and spontaneously fermented beers are growing in popularity in the craft beer industry. Most of these beers are fermented by the use of either pure cultures of unconventional yeast and bacteria or spontaneous fermentation using mixed local microflora. This study examined the potential of using pure strains of new isolates of wild yeast in the fermentation of a unique beer. The microbial communities from the fruit of pindo palm, loquat, hackberry and blackberry were collected in liquid culture, then plated for isolation. Ten isolates were selected for further analysis. Strains were identified by restriction fragment length polymorphism (RFLP) analysis and analysed for growth in a simple liquid media, fermentation in a complex media, alcohol tolerance and acid tolerance. Despite identification of some strains as the same species, they displayed a wide range of physiological properties. All strains were tolerant of pH values as low as 2.4, but none were tolerant of pH 1.9. Alcohol tolerance of different strains varied from 6 to 12%. Several strains had properties that suggest potential as primary fermenters, including the alcohol fermentation of a beer wort. Organoleptic properties of beers fermented with several of the strains demonstrated potential for commercial brewing. Copyright © 2014 The Institute of Brewing & Distilling     

Phenolic Profiles and Total Antioxidant Capacity of Marketed Beers in Serbia

The aim of this research was to determine the total phenolic and flavonoid contents as well as to measure antioxidant activity of 24 different commercial beers consumed in Serbia. The major phenolic acids (gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, sinapic acid, salicylic), (+)-catechin, and (-)-epicatechin were also determined by high pressure liquid chromatography method using a photodiode array detector. Gallic acid, ferulic acid, and protocatechuic acid are the most abundant phenolic acids in all samples, followed by (+)-catechin. The total phenolic content was determined using the Folin-Ciocalteu assay. The total flavonoids were measured using spectrophotometrics as the aluminum chloride assay. The results showed that the highest total phenolic and flavonoid contents were established in dark and light beer samples. 2,2-Diphenyl-1-picrylhidrazyl radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical cation scavenging activity, and ferric reducing/antioxidant power were used to assess the antioxidant potential of beers. These assays, based on different chemical mechanisms, were selected to take into account the wide variety and range of action of antioxidant compounds present in selected beer samples. All beers showed antioxidant power, but a wide range of antioxidant capacities was observed. Statistical differences between ferric reducing-antioxidant power and the other two antioxidant capacity assays were confirmed. This study will be useful for the appraisal of phenolic profile and antioxidant activities of various beers, and it will also be of interest for people who like drinking this beverage.     

Lachancea thermotolerans as an alternative yeast for the production of beer

The ability of Lachancea thermotolerans strains to ferment brewer's wort has been investigated. Initial fermentations with three L. thermotolerans strains compared the use of maltose and maltotriose, as well as production of glycerol and lactic acid and pH evolution over the course of the fermentation. The most promising strain was subsequently tested for additional traits important for beer production, including pitching rate, generational capacity, foam stability, hop tolerance, vicinal diketone production, oxygen requirement and flocculation. These tests suggest that L. thermotolerans may be a good choice for producing sour beers in a single fermentation step without the use of lactic acid bacteria. Copyright © 2016 The Institute of Brewing & Distilling     

不同原浓啤酒中有机酸的含量分析

以相同原料配比,用下面发酵法酿造6 0、6 5、7 0、7 5、8 0与10 0°P啤酒。样品总酸随原浓上升而提高,原浓低于7 5°P时,啤酒酸味明显。用反相高效液相色谱(RP -HPLC)法在啤酒中检测出了10种有机酸:草酸、酒石酸、丙酮酸、苹果酸、α酮戊二酸、乳酸、乙酸、柠檬酸、富马酸与琥珀酸,总量为738 17～799 5 0mg/L ,各样品间有机酸含量差异明显。琥珀酸含量最高;其次是柠檬酸、苹果酸、丙酮酸、乳酸与草酸。草酸、丙酮酸随着原浓的增加而升高。7 0、7 5、8 0、10 0°P啤酒中乳酸含量相近,6 0、6 5°P啤酒中乳酸含量急剧上升。研究结果表明,啤酒酵母产酸受原浓与发酵度的影响     

FLAVOUR STABILITY OF ALES BREWED USING HYDROLYSED MAIZE SYRUP—SENSORY AND ANALYTICAL ASPECTS

Whereas ales brewed entirely from malt had flavour-lives of 12 weeks, those produced from 70% malt/30% hydrolysed maize syrup had flavour-lives of at least 25 weeks. The latter beers were of sound flavour and quality, and no difficulties were experienced during their production. Their initial flavour was similar to that of beers brewed using an all-malt grist. Analysis by gas chromatography coupled mass spectrometry showed that the all-malt beer underwent a greater degree of change during natural aging than did the beer brewed with maize syrup. A number of compounds, including a series of glycerol/acetaldehyde acetals, have been identified for the first time in beer; the latter compounds were found to increase in level during aging.     

THE QUANTITATIVE DETERMINATION OF GLYCEROL IN BEER BY GAS-LIQUID CHROMATOGRAPHY

The glycerol present In beer in conjunction with the constituent sugars was resolved as the trimethylsilyl derivative on a 2 ft. × 1/4 in. o.d. stainless steel column packed with 1% OV 17 on Chromosorb W-H.P., 80–100 mesh. Complete separation and quantitative estimation were obtained. Coefficients of variation for determination of glycerol in aqueous solution were found to be 2·7% for machine operation alone and 4·1% for the total procedure. For glycerol determination in the presence of beer the coefficient of variation for the total procedure was doubled. A survey of Canadian beers indicated a glycerol level of approximately 2 mg./ml. and showed no trend according to type, locality or brand. Taste test studies revealed the threshold level of glycerol detection in a test beer to be 10 mg./ml. The addition of glycerol to beer above and below the threshold level was found to modify the flavour of the product.     

啤酒中有机酸含量的RP-HPLC检测条件优化及其酿造过程中动态分析

该研究对反相高效液相色谱（RP-HPLC）法测定啤酒中有机酸含量的方法进行优化,最终确定了RP-HPLC法测定啤酒中草酸、乳酸、酒石酸、乙酸、苹果酸、α-酮戊二酸、抗坏血酸、柠檬酸、琥珀酸9种有机酸的检测条件,并结合发酵机理对啤酒酿造过程中的有机酸含量动态变化进行分析。结果表明,RP-HPLC优化条件为：检测波长215 nm、流动相缓冲液0.10 mol/L KH2PO4、pH值3.0、流速0.6 mL/min。有机酸在质量浓度0.2～400.0 mg/L范围内线性关系良好（R2均＞0.99）,加标回收率79.3%～110.0%,精密度试验结果相对标准偏差（RSD）为0.3%～11.5%,表明该方法精密度高、准确性良好。在啤酒酿造过程中有机酸总量及乙酸、琥珀酸、苹果酸、乳酸、柠檬酸、α-酮戊二酸含量呈现先增长后平稳的趋势,草酸、抗坏血酸、酒石酸含量变化相对平稳。