Analysis of flavour compounds in beer with extruded corn starch as an adjunct

Extruded corn starch (ECS) was used as an adjunct during beer fermentation and the fermentable sugars in the wort made with ECS and cooked corn starch (CCS) were determined using high‐performance liquid chromatography. The flavour compounds of beer made using ECS and CCS were determined using headspace solid‐phase micro‐extraction gas chromatography–mass spectrometry, and eight volatile compounds in ECS and CCS beer were quantified using gas chromatography (GC). Five fermentable sugars (fructose, glucose, sucrose, maltose, maltotriose) were detected in both samples, and their content in ECS wort was higher than in CCS wort, except for maltose. Seventy‐three flavour compounds were identified and quantified in ECS beer, while 58 compounds were determined in CCS beer. Both ECS and CCS can be used to produce beer; however, the concentration of characteristic beer flavour compounds in ECS beer was higher than in CCS beer. Copyright © 2018 The Institute of Brewing & Distilling     

Analysis of flavour compounds in beer with extruded sorghum as an adjunct using headspace solid‐phase micro‐extraction and gas chromatography–mass spectrometry

Sorghum is a widely used adjunct that is used in the production of beer and increasingly affects beer flavour as the amount added increases. The aim of this work was to establish a simple, solvent‐free technique, without derivatization, to analyse flavours and typical volatile compounds present in extruded and unextruded sorghum beer, and to compare the flavour differences of the two types of beer. Headspace solid‐phase micro‐extraction gas chromatography–mass spectrometry was used to determine the flavours in the two beers and eight typical volatile compounds were quantified using GC. Forty‐five flavour compounds were identified and quantified in extruded white sorghum beer, while 31 flavour compounds were identified in unextruded white sorghum beer. Extruded or unextruded white sorghum can be used to produce ale beer, but the primary flavour content in the extruded white sorghum beer was higher than in the unextruded white sorghum beer. Copyright © 2016 The Institute of Brewing & Distilling     

全二维气相色谱技术在酒类挥发性化学成分检测中的应用

酒的风味是评价酒质量品质的重要指标,其中的挥发性化学成分是影响风味的关键因素。在酒类挥发性化学成分检测中,与 常用的一维气相色谱相比,全二维气相色谱技术极大地提高了色谱的分离能力和分析速度,具有广泛用途。 该文综述了全二维气相 色谱在中国白酒、葡萄酒、啤酒等不同酒类挥发性物质检测中的应用,为解析不同酒的风味特征提供物质基础和方法参考。     

Determination of flavour compounds in beer using stir‐bar sorptive extraction and solid‐phase microextraction

The analysis of volatile compounds in beer is important for quality control in the brewing industry. In this study, stir‐bar sorptive extraction (SBSE) and solid‐phase microextraction (SPME), two solvent‐less enrichment techniques, were applied in combination with gas chromatography flame ionization detection (GC/FID) for the determination of four flavour compounds (isoamyl acetate, ethyl hexanoate, benzaldehyde, myrcene) in beer. Limits of detection, linearity and repeatability of both methods were determined using standard ethanol solutions, while accuracy was determined by conducting recovery tests on commercial beer samples. Both methods were characterized by high linearity (r > 0.996) and repeatability (RSD = 1.76–10.66%). When both methods were compared, higher recoveries were obtained by SBSE, with limits of detection 1.8–2.8 times lower compared with SPME. In the analysis of commercial beer samples using both methods, SBSE analysis resulted in higher recoveries, therefore demonstrating promise for the analysis of beer volatiles. Copyright © 2015 The Institute of Brewing & Distilling     

N-nitrosodimethylamine analysis in Estonian beer using positive-ion chemical ionization with gas chromatography mass spectrometry

N-nitrosodimethylamine (NDMA) is a potent animal carcinogen that has been detected in trace levels in beers. A total of 264 beer samples were analyzed for their NDMA content. For cleaning of the sample the two-step solid-phase extraction with Extrelut and Florisil sorbents were used. NDMA was separated by gas chromatography and detected by positive-ion chemical ionization using ammonia as reagent gas. The HP 6890 Plus GC/HP 5973 MSD with positive-ion chemical ionization option was used in the selected ion-monitoring mode. The limit of detection for NDMA using this method was 0.15 ppb with about 70–80% recovery. Of 158 Estonian beers analyzed during 2003–2004, the average NDMA level was found to be 0.20 ppb. Of 106 imported beer samples the average NDMA level was found to be 0.21 ppb.     

PHYSIOCHEMICAL PROPERTIES AND DETERMINATION OF BIOGENIC AMINES IN KOREAN MICROBREWERY BEER PRODUCTS

In this study, 20 microbrewery beer samples collected from different regions in Korea were analyzed for their contents of biogenic amines as well as for their physiochemical properties (pH, acidity and alcohol content). The separation of biogenic amines involved derivatization with dansylchroride followed by subsequent analysis by high‐performance liquid chromatography. As a result, biogenic amines such as tryptamine (nd–1.10), 2‐phenylethylamine (nd–0.69), putrescine (0.53–3.56), cadaverine (0.10–1.56), histamine (0.13–2.65), tyramine (0.10–4.96), spermidine (nd–2.29) and spermine (nd–1.02) mg/100 mL were detected in the analyzed beer samples. Agmatine was not detected in any of the beer samples processed. The pH, acidity and alcohol contents of the tested beer samples were found in the range of 3.92–4.57, 0.17–0.38 and 3.8–7.0%, respectively. It was found in this study that threshold toxic level of the beer products analyzed was at acceptable consuming limit.     

Proteins and amino acids in beers,their contents and relationships with other analytical data

Fluorometry, ion-exchange chromatography, electrophoretic separations and Fourier transform–infrared (FT–IR) spectra were used to determine and characterize amino acids and proteins in 15 different beer samples. Proteins precipitated by ammonium sulfate yielded complex electrophoretic patterns. The major bands corresponded to 45–40 kDa as determined by a two-dimensional gel electrophoresis (2-DE). Proteins and some amino acids are partially responsible for nutritional value and stability of beer. Therefore, electrophoretic analysis revealed that protein characterization of beer during all technological stages might be useful in its quality. FT–IR protein spectra showed the presence of I, II and III amide bands. Protein distribution and amino acid composition of beer differ significantly, depending on the raw materials and enzymatic reactions used in beer technology. Concentrations of histamine (3.02–3.23 mg/l), proline (1.60–3.13 mg/l) and tyramine (3.61–7.4 mg/l) increased during beer fermentation. Statistically significant change was registered in the protein content of the final product, which was less than that in wort (p<0.005). Levels of tyramine and proline, which were higher than in wort (p<0.025) showed significant changes. This investigation shows that, in Israeli, Mexican and Brazilian beers, the contents of protein and amino acids are in accordance with the international standards.     

Determination of several flavours in beer with headspace sampling–gas chromatography

In order to determine flavours (diacetyl, pentanedione, acetoin and acetaldehyde) in beer, gas chromatography coupled with headspace sampling technique was developed in our laboratory. The calibrations were accomplished by six level standard addition methods, and relative coefficients were ?0.999. Repeatability experiments were accomplished by detecting 20 successive same standard samples, which showed that detection precision was <2% relative standard deviation (RSD) for three flavours (diacetyl, pentanedione and acetaldehyde), and detection precision of acetoin was <2.5% (RSD). Four flavours gradually increased and then decreased during the process of fermentation, and they leveled off when the fermentation was over. The ratio (diacetyl/pentanedione) reflected the degree of contamination: normal beer had a ratio of approximate 1; the ratio (diacetyl/pentanedione) was higher than 1, displaying that beer was contaminated by microbes. Our data suggested that gas chromatography coupled with headspace sampling technique could be used successfully to determine flavours (diacetyl, pentanedione, acetoin and acetaldehyde) in beer.     

Application of response surface design to optimise the chromatographic analysis of volatile compounds in beer

Solid‐phase microextraction (SPME) combined with gas chromatography and mass spectrometry (GC–MS) is a rapid method for the analysis of different aromatic compounds in beer. However, chromatographic systems are affected by different parameters and optimization is time‐consuming process, but essential for establishing optimal conditions for the quantification of analytes. An automated system consisting of headspace (HS)–SPME extraction combined with GC–MS was optimized for the determination of 19 volatile compounds responsible for important flavours and off‐flavours of beer. The optimisation process consisted of two steps: the SPME fibre type was chosen, and subsequently four extraction parameters (temperature, time, sodium chloride concentration and pH) were optimised by a central composite design model. After optimisation, standard compounds were validated with relative standard deviations not exceeding 15%_rel. The square of correlation coefficient for the calibration curves was ≥0.9559, indicating a linear response and the suitability of these HS‐SPME conditions. Copyright © 2018 The Institute of Brewing & Distilling     

黄秋葵粉对面团和面包质构特性的影响

为研究黄秋葵粉对面团和面包质构特性的影响,按不同添加量(1%~5%)将3种粒度(60、100、200 目)的黄秋葵粉分别添加到小麦粉中,制作面团和面包,对面团和面包质构(硬度、弹性、咀嚼性和回复性)特性进行测定。结果表明:随着黄秋葵粉添加量的增加,面团和面包的硬度和咀嚼性均提高,面团和面包的弹性和回复性均降低;黄秋葵粉的粉碎粒度对面团和面包的质构也有一定影响,在相同的添加量水平下,随着黄秋葵粉粒径的减小,面团的硬度、弹性、咀嚼性和回复性均降低,但变化并不明显;在相同的添加量水平下,黄秋葵粉的粒径变化对面包的硬度、弹性、咀嚼性和回复性有一定影响,但变化并不明显。该研究对开发黄秋葵面包具有一定的指导意义。     

APPLICATIONS OF FAST PROTEIN LIQUID CHROMATOGRAPHY (FPLC) TO THE ANALYSIS OF THE NITROGENOUS CONSTITUENTS OF BEER

The nitrogenous constituents of beer were investigated by several Fast Protein Liquid Chromatography (FPLC) techniques. Size exclusion chromatography of dialysed beer material using columns of Superose 6 and Superose 12 suggested that beer polypeptide material was distributed across a wide relative molecular mass (Mr) range with discrete fractions of high Mr (Mr 300 000, Mr 500 000), Mr c60 000, Mr c40 000 and relatively low Mr (Mr 5 000–20 000). The composition of fractions Mr >40 000 and Mr 40 000–60 000 was investigated by ion exchange chromatography. Differences were detected in the elution profiles of fractions prepared from beers brewed from grists comprising 100% malt, 80% malt plus 20% torrfied wheat and 100% malted wheat consistent with differences in the polypeptide composition of these fractions. The Superose 12 column, although designed for the fractionation of high molecular weight components, also provided a method of fractionating low molecular weight nitrogenous materials directly from beer (for example fractions containing purine nucleosides). Reverse phase chromatography was employed in the analysis of beer peptides and demonstrated the complex composition of beer peptide fractions.     

打瓜啤酒生产工艺的优化

在啤酒生产过程中添加打瓜,通过单因素和正交试验对打瓜啤酒酿造工艺进行优化,利用电子舌、气相色谱（GC）和高效液相色谱（HPLC）测定打瓜啤酒味觉特征、香味物质和有机酸。结果表明,打瓜啤酒最佳生产工艺条件为打瓜汁添加量18%,酵母添加量为1.0 g/L、初始pH值5.2、主发酵温度10.5 ℃。在此优化条件下,打瓜啤酒的感官评分为93.3分。打瓜啤酒丰富度饱满,整体滋味偏咸味和鲜味;通过GC在打瓜啤酒中检测出10种香气成分,其中醛类物质1种、醇类物质4种、酯类物质5种;HPLC检测分析的9种有机酸均有检出,其中柠檬酸含量最高,为（9.30±0.038）g/L,是打瓜啤酒有机酸组成的主体。     

Quantification of Six Phthalates and One Adipate in Luxembourgish Beer Using HS-SPME-GC/MS

A simple, low-cost and sensitive method for the determination of six phthalate acid esters (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate and dioctyl phthalate) and one adipate (bis(2-ethylhexyl) adipate) in beer has been developed using head-space solid-phase microextraction (HS-SPME) followed by gas chromatography coupled to mass spectrometry (GC/MS). SPME conditions were optimised, and optimum extraction parameters were found to be 95 °C at 100 min, without addition of NaCl. Matrix interference was avoided by using a deuterated internal standard (ISTD). Limits of detection ranged from 0.006 to 0.590 μg/L. The method showed good linearity with coefficients of determination ranging from 0.963 to 0.999 and satisfactory accuracy (74–101 %) and repeatability (3.56–27.86 %) values. The method was applied to 15 samples of beer from Luxembourgish breweries, stored in different containers (can, glass and aluminium bottle), and phthalates were detected in all samples with concentrations as high as 61.56 μg/L for total phthalates. The exact origins of phthalates in beer were difficult to determine from the data in this study, though the brewing and bottling process seems to be a major contributor.     

啤酒酿造过程中萜烯醇类化合物变化规律

采用基于顶空固相微萃取-气相色谱质谱技术(HS-SPME/GC-MS)建立的啤酒中酒花物质的检测方法,跟踪了啤酒酿造过程中源自酒花的5种萜烯醇类香气化合物的变化规律,初步为啤酒厂酒花配方及工艺调整奠定了理论基础。通过对糖化过程中不同酒花配方、不同煮沸方式及酒花添加工艺对冷麦汁中萜烯醇类化合物含量影响的研究,发现冷麦汁中的萜烯醇类化合物主要受最后一次添加酒花的添加量和添加时机影响,最后一次酒花在煮终回旋前添加较煮终前10 min添加,更利于萜烯醇类化合物在冷麦汁中的保留,这与国外的late-hopping工艺相一致;与煮终前10 min最后一次添加相比,在煮终回旋前最后一次添加酒花能使冷麦汁中里那醇含量提高209.4%,α-萜品醇为91.2%,香叶醇为31.4%,橙花醇175.0%。通过研究发酵过程中萜烯醇类化合物的变化规律,发现5种萜烯在发酵过程中呈上升趋势,且它们之间可能被酵母相互转化。     

Changes in the hop-derived volatile profile upon lab scale boiling

Hop terpenes might be oxidized during kettle boiling into more water soluble compounds that could contribute to ‘hoppy’ aroma of kettle hopped lager beers. Our current research proves that the boiling process induces significant changes in the hop oil volatile profile. The discrimination between volatile profiles of unboiled and boiled hop essential oil was evaluated via principal component and cluster analysis (PCA and CA). HS–SPME–GC–MS analysis revealed quantitative changes (e.g. increases in the levels of oxygenated α-humulene and β-caryophyllene derivatives) as well as qualitative changes (i.e. detection of compounds, not found in unboiled hop essential oil) in the hop oil volatile profile upon boiling. Many of these compounds were previously found in lager beer and may therefore contribute to beer flavor. Interestingly, the analytical difference between unboiled and boiled hop essential oil proved to be more pronounced as the initial hop essential oil concentration used for boiling was increased. In addition, lager beers spiked with boiled hop oil were described as ‘hoppy/spicy’ during sensory evaluations. Therefore, the newly formed products and hop oil constituents that are characterized by an increased recovery after boiling, are candidate compounds for ‘hoppy’ aroma in real brewing practice.     

γ-氨基丁酸对黄秋葵采后品质及生理特性的影响

为研究γ-氨基丁酸(γ-aminobutyric acid,GABA)处理对采后秋葵常温贮藏品质及生理特性的影响,分别用不同浓度(5、10、15 mmol/L)GABA水溶液浸泡黄秋葵3 min,以清水处理为对照,室温下(25℃)贮藏,并定期测定黄秋葵贮藏过程中失重率、叶绿素、V_C含量、丙二醛含量、抗氧化酶活性等生理指标的变化。结果表明,10 mmol/L的GABA处理效果最好,能够明显减缓黄秋葵的采后失水,延缓叶绿素和V_C的降解,能明显提高过氧化氢酶(Catalase,CAT)和超氧化物歧化酶(Superoxide dismutase,SOD)活性,降低过氧化物酶(Peroxidase,POD)活性和减少丙二醛(Malondialdehyde,MDA)的积累。其中贮藏21 d的叶绿素含量比对照组(0.074 mg/g)高出37.49%,V_C含量比对照组(3.61 mg/100 g)提高了69.23%,SOD活性相比对照组(47.05 U/g)提高了30.35%。相关性和主成分分析表明,黄秋葵贮藏时间和失重率、MDA含量呈极显著正相关(P<0.01),与叶绿素含量、V_C含量、CAT活性和POD活性呈极显著负相关(P<0.01);黄秋葵贮藏品质和综合评价指数均随贮藏时间增加而逐渐降低,而不同浓度的GABA处理能延缓黄秋葵贮藏品质的下降。这些结果表明适宜浓度的GABA处理可以延缓黄秋葵果荚的采后衰老,并保持良好的采后品质和营养价值,为GABA的应用及黄秋葵的采后保鲜提供理论依据。     

Improvement of beer flavour with extruded rice as adjunct

Extruded rice used as adjunct for beer fermentation was prepared using a single‐screw extruder. Extrusion pretreatment facilitated the saccharification and gelatinization of the rice starch as well as the formation of a glassy cellular structure, which was evaluated through scanning electron microscopy analysis. The effects of different parameters, including barrel temperature, water content, nozzle diameter and screw speed, as well as their interactions with rice expansion rate, were evaluated by response surface methodology to determine the optimum extrusion conditions. Extruded rice was acquired using the optimum extrusion parameters (water content, barrel temperature, screw speed and nozzle diameter of 22.4%, 103°C, 8 mm and 191.6 rpm, respectively), and the expansion rate reached 275.1%. The effect of the extruded rice adjunct on beer flavour compounds was investigated by comparing flavour compounds with those of traditional rice‐adjunct beer through sensitive static headspace–capillary gas chromatography spectrometry. The contents of esters, a highly important flavour group, in extruded‐rice‐adjunct beer (ethyl acetate, isoamyl acetate, ethyl hexanoate and ethyl caprylate at 11.6, 2.4, 0.2 and 0.3 mg L⁻¹, respectively) were higher than those of the traditional rice‐adjunct beer. The contents of high alcohols were lower in the traditional rice‐adjunct beer than those in the extruded‐rice‐adjunct beer, but both levels satisfied the national standard for beer. Gas chromatography–mass spectrometry was employed to identify the flavour compounds of both beer samples through headspace–solid‐phase microextraction. Copyright © 2017 The Institute of Brewing & Distilling     

Rice vinegars of different origins: discriminative characteristics based on solid‐phase microextraction and gas chromatography with mass spectrometry,an electronic nose,electronic tongue and sensory evaluation

Eight kinds of commercial rice vinegars from Korea, China and Japan were selected to evaluate their flavour‐related discriminative characteristics based on solid‐phase microextraction and gas chromatography with mass spectrometry (SPME/GC–MS), an electronic nose (e‐nose), electronic tongue (e‐tongue) and subjective sensory evaluation. Principal component analysis patterns based on SPME/GC–MS provided a clear categorical discrimination among the vinegars of three origins. The distribution patterns of the samples were similar between SPME/GC–MS and e‐nose analyses and Korean vinegars were clearly discriminated. A high correlation coefficient was determined between SPME/GC–MS and e‐nose on acetaldehyde (0.948) and diacetyl (0.970). e‐Tongue‐based principal component analysis patterns were subdivided into three regions according to the origin, and Chinese vinegars were clearly discriminated. Sensory panelists recorded origin‐specific scores on flavours for all the samples. In conclusion, SPME/GC–MS, e‐nose and e‐tongue analyses may be useful for discrimination of flavour profiles of rice vinegars of different producer origin. Copyright © 2017 The Institute of Brewing & Distilling     

食品包装薄膜残留苯和甲苯在食品中的迁移研究

为了解食品包装薄膜溶剂残留的危害现状及包装各类食品的安全性,试验采用气相色谱法对市场中常见的9种食品包装薄膜中苯和甲苯的残留及两者在包装过程中对苹果、油条、煎饺、啤酒的迁移进行了研究。结果表明,未检出苯或甲苯的薄膜在其相应包装的食品中也未检出苯或甲苯;在苹果和啤酒中均为检出两者;迁移量与包装时间有密切关系,油条和煎饺在包装过程中的最初10min均未检出两者,包装60min时最大迁移量达到1.168mg/kg。     

Changes in protein molecular weight during cloudy wheat beer brewing

To investigate the changes in protein in cloudy wheat beer (CWB) brewing, the molecular weight (M_w) of protein components in wort, fermenting wort, beer and beer foam were analysed by high‐performance size‐exclusion chromatography. It was found that the M_w of protein during brewing was mainly distributed between 100 and 0 kDa. From mash to the final beer, the most abundant protein component was the 7.6–2.1 kDa fraction, which occupied more than 40% of the total protein. The extraction of soluble protein from malts into wort mainly focused on the protein rest process, where the 100.0–32.1 and 7.6–2.1 kDa fractions increased significantly. In addition, the 100.0–13.2 kDa fraction was the predominant thermolabile protein that decreased during lautering and boiling. The dominant protein constituting the fine coagulum, the 100.0–13.2 kDa fraction, also decreased during fermentation and maturation. The CWB, defoamed CWB and CWB foam had similar protein M_w distributions, while the CWB foam concentrated much more protein and the 7.6–2.1 kDa fraction was the major protein in the CWB foam. Copyright © 2015 The Institute of Brewing & Distilling