AN IMMUNOCHEMICAL ANALYSIS OF BEER FOAM

Beer foam produced in a continuous foaming tower in volumes representative of commercial dispense, was analysed by immunoelectrophoretic and immunoblotting techniques to identify antigens involved in foam structural stability. In crossed immunoelectrophoresis (CIE), only one antigen precipitated from foam in the homologous foam antiserum. This antigen was shown to be of malt origin by rocket-line immunoelectrophoresis and was also present in 11 commercial beers (5 bitters, 4 lagers and 2 stouts). However, the foam preparation separated into more than 20 polypeptides by SDS polyacrylamide gel electrophoresis. Immunoblotting showed that at least 12 of these reacted with foam antiserum and that they originated from either malt or yeast. Similar polypeptides were also identified in the antigen precipitated in CIE, suggesting that these polypeptides were probably present in the foam as a complex. It is concluded that the stability of foam reflected molecular interactions between these polypeptides (and possibly other components such as carbohydrates) in the liquid film of the bubble structure.     

VARIETAL DEPENDENCE OF HOP FLAVOUR VOLATILES IN LAGER

A series of lagers brewed with single hop varieties was analysed via extraction and gas chromatography/mass spectrometry. Each hop variety contributed a small number of unique flavour compounds to the beers. Significant, reproducible differences were found between the concentrations of individual hop compounds and hop compound classes in the different beers.     

A Comparison of Three Methods for the Assessment of Foam Stability of Beer

Three methods for measuring foam stability were assessed using nine different beers. The methods were the NIBEM instrument of Haffmans, the device marketed by Steinfurth and the manual procedure developed by Constant. There were reasonable‐to‐good correlations when the foam stability of all the beers, as determined by the individual methods, were compared one with another. However when individual beers were studied, it appeared that different techniques rank them in somewhat different sequences. All of the methods demonstrated the superior foam stability of examined ales over lagers, however there were some differences in ranking of beer foam quality, in particular with the beers bittered with reduced iso‐α‐acids, which performed better when assessed by methods that quantified the foam itself, rather than drainage.     

Relationships of Sensory Bitterness in Lager Beers to Iso‐α‐Acid Contents

Iso‐α‐acids and their chemically modified variants play a large role in evoking the bitter sensory attributes of lager character, but individual consumers may vary in their perception of bitterness. Sixteen lagers were scored in rank‐rating for bitterness by 14 trained assessors and the concentrations of the six bitter components in these beers were determined by high performance liquid chromatography. Relationships between bitterness intensity and the bitter components were modelled well using partial least square regression with a correlation value of 0.92. When 8 assessors carried out time‐intensity scoring of bitterness, profiles for single products were very different. However, single assessor profiles for multiple products showed qualitative similarities but quantitative differences. That individual assessors perceived bitter characters differently in relation to time has implications for new product development.     

Investigation of sensory attributes contributing to beer preference among Koreans by using fuzzy reasoning

The sensory attributes which contribute to preferences for different beers amongst Koreans were investigated and ranked in terms of their priority. The priority sensory attributes were those with high contribution weights to overall preference. Three sets of contribution weights of the attributes were determined by fuzzy reasoning from the votes through a survey from the groups of all consumers (group I), lager‐preferring consumers (group II) and ale‐preferring consumers (group III). In order to investigate the most reliable contribution weights, the overall preferences of 20 beers were sensory‐evaluated and compared with those estimated by fuzzy reasoning with the contribution weights. When the contribution weights of the attributes were most reliable, the estimates were equal to the total preferences of the samples. It was found that the estimates from groups II and III agreed with the experimental data better than those from group I. This indicates that the contribution weights from group I were less reliable, most likely because there are several groups of Korean consumers with a wide variety of preferences. Therefore, Korean priority sensory attributes for groups II and III were as follows. For group II, the attributes with the contribution weights in decreasing order were found to be ‘total CO₂’ > ‘bitterness’ > ‘duration aftertaste’ > ‘aromatic’ > ‘foam volume’ > ‘density’; for group III, the contribution weights were in the order of ‘aromatic’ > ‘total CO₂’ > ‘bitterness’ > ‘duration aftertaste’ > ‘density’ > ‘foam volume’. These findings will help develop beers appropriate for Korean tastes. Copyright © 2017 The Institute of Brewing & Distilling     

Relationship of Sensory Staleness in Two Lagers to Headspace Concentrations of trans‐2‐Nonenal and Three Staling Aldehydes

Key compounds in lager staling include furfural, hexanal, 5‐ hydroxymethyl furfural (5‐HMF), and trans‐2‐nonenal. Quantitative data of headspace concentration in two lagers — one premium at 5% (abv), the other a standard product at 4% (abv) — were obtained by solid phase microextraction (SPME) followed by gas chromatography using a mass selective detector (GCMS). The concentrations of the aldehydes were used to predict overall stale scoring from sensory assessor data, of lagers stored at 4, 12, 30, and 37°C for 7, 14, 21 and 28 days. Concentrations of all four aldehydes increased with time of storage and with higher temperatures. Correlation coefficients for prediction of staleness in the premium lager were similar at 0.81 and 0.84 for partial least square regression (PLS1) and artificial neural network (ANN) modelling respectively, and the latter showed a lower root mean square error (RMS error). For the standard product, the correlation coefficients were 0.72 and 0.86, with ANN showing lower RMS error respectively. In both PLS models, E‐2‐ nonenal had high regression coefficients and 5‐HMF lower coefficients. Furfural and hexanal differed in contributions to the lagers.     

Determination of Prolamins in Beers by ELISA and SDS‐PAGE

Coeliac disease is triggered by exposure to the prolamin protein fraction of wheat, barley, or rye. The prolamin content of five lager beers and one wheat beer were analyzed by sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting and seven lager beers and three wheat beers were analyzed by enzyme‐linked immunosorbent assay (ELISA). Most of the lager beers were made from barley and some had varying amounts of rice or corn as adjuncts. One of the beers was “gluten‐free”, having been produced from corn and buckwheat without barley. The lager beer samples were gel‐filtered before ELISA or SDS‐PAGE analysis. Prolamin proteins were found in all but one beer which was made of corn, rice and barley and which was not the “gluten‐free” beer. ELISA analysis was done using a commercially available gluten assay kit. For lager beers, a barley prolamin standard for ELISA was propanol‐extracted from barley malt instead of using the prolamin standard of the gluten assay kit. As expected, the wheat beers contained much higher amounts of prolamins than the lager beers. The samples were studied by SDS‐PAGE to identify different prolamin fractions. Proteins having a relative molecular mass in the range of 8000–17,000 and 38,000 and above were detected in immunoblotting by the prolamin sensitive antibody in the lager beers.     

免疫亲和净化-液相色谱-串联质谱法测定贝类中腹泻性贝类毒素

建立贝类中腹泻性贝类毒素的免疫亲和净化-液相色谱-串联质谱分析方法。样品采用80%甲醇溶液提取,选择磷酸盐缓冲液与提取液(4∶1,V/V)混合稀释后,免疫亲和选择专一净化,液相色谱-串联质谱分析。根据腹泻性免疫亲和柱的使用特性,对上样液、淋洗液、洗脱液等参数进行优化。质谱采用电喷雾负离子电离,多反应监测模式,外标法定量。3种分析物在1.0~100μg/L质量浓度范围内线性相关系数均大于0.996,对应的检出限和定量限均为0.3μg/kg和1.0μg/kg,平均回收率为82.7%~94.3%,相对标准偏差为0.70%~7.61%。本方法基质干扰小、净化效果强、灵敏度高,适合贝类中腹泻性贝类毒素的分析测定。     

高效液相色谱法测定酒中的赭曲霉毒素A

研究了单克隆免疫亲和柱-高效液相色谱法测定酒中赭曲霉毒素A的方法。脱气后的酒类样品用1%PEG和5%NaHCO3的水溶液稀释,然后通过Ochra Test免疫亲和柱净化,净化液经Hypersil BDS C18柱反相色谱柱分离、荧光检测器检测、外标法定量。对添加不同含量的赭曲霉毒素A进行6次反复实验,得其平均回收率为92.8%-99.5%,RSD%〈10,最低检测限为0.04ng/mL,线性范围为0.1-10ng/mL。     

Impact of colour adjustment on flavour stability of pale lager beers with a range of distinct colouring agents

The impact of colour adjustment on the flavour stability of five pale lager beers with a range of colouring agents such as specialty malts, colouring beer and artificial caramel colourant was investigated. The research focused on determination of the endogenous anti-oxidative potential (EAP) of the beer samples using a novel Electron Spin Resonance (ESR) method. The results were correlated with the concentration levels of a portfolio of compounds formed during beer ageing, which were detected and quantified by GC–MS. The beer samples were also assessed by the ICBD sensory panel. Additionally, the quantification of organic radicals of the specialty malts and the roasted barley were conducted by ESR (whole intact kernel and milling fraction measurement). Based on the results of this holistic approach, a colouring agent was identified that enhanced the flavour stability of pale lagers based on the final beer’s physical-, chemical-, and sensory-properties.     

苏丹红Ⅰ免疫亲和柱的研制与鉴定

以羧基化的琼脂糖凝胶4FF为载体,采用碳化二亚胺法偶联抗苏丹红Ⅰ(SudanⅠ)单克隆抗体,制备苏丹红Ⅰ免疫亲和柱(IAC)。将SudanⅠ样品过免疫亲和柱,乙腈洗脱后以高效液相色谱法(HPLC)检测,紫外检测波长为478nm,流动相为0.1%甲酸水溶液-乙腈-0.1%甲酸乙腈溶液-丙酮(体积比为21.25:3.75:60:15)。抗SudanⅠ单克隆抗体免疫亲和柱以0.3g带羧基的琼脂糖凝胶4FF与1mg SudanⅠ单抗偶联,柱容量为1.6μg。辣椒粉以0.25～3mg/kg水平添加SudanⅠ标准品,平均回收率为44.52%～77.40%,相对标准偏差为4.6%～8.3%。信噪比(RSN)为3:1时的最低检测限为15ng/mL。本实验成功制备出苏丹红免疫亲和柱。     

Wheat Variety and Barley Malt Properties: Influence on Haze Intensity and Foam Stability of Wheat Beer

Laboratory wheat beers were brewed with different wheat varieties of different protein content (8.7–14.4%) and with five different barley malts, varying in degree of modification (soluble protein: 3.9–6.9%). In a first series of experiments, it was investigated whether wheat positively influences the foam stability, a major characteristic of wheat beers. NIBEM and Rudin (CO₂) foam analyses revealed that the effect of wheat on foam stability depended on the barley malt used for brewing. When using malt with high foaming potential, wheat exerts a negative influence. However, wheat added to over‐modified malt with less foam promoting factors, ameliorates beer foaming characteristics proving that wheat contains foam active compounds. In addition, Rudin (N₂) values suggested that wheat positively influences foam stability by decreasing liquid drainage, probably caused by a higher beer viscosity and/or a finer foam bubble size distribution. Furthermore, the haze in wheat beers, which is another important quality characteristic of these beers, was investigated. Permanent haze readings of the 40% wheat beers were lower than 1.5 EBC haze units. For 20% wheat beers, an inverse relation between the permanent haze (9.4–19.3 EBC haze units) and the protein content of the wheat was established. The barley malt used for brewing also influenced permanent haze readings. A positive correlation between the modification degree of the malt and the permanent haze intensity was found. It was concluded that the choice of raw materials for wheat beer brewing considerably influences the visual properties of the beer.     

Effects of high hydrostatic pressure on shelf life of lager beer

Filtered bright lager beer samples were either treated with high hydrostatic pressure (HHP, 350 MPa for 3 and 5 min at 20 °C) or conventional heat pasteurization (60 °C for 15 min). A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color (p<0.05). However HHP-treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples at the end of the storage period. The microbiological stability of HHP-treated beers was the same as that of heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Although more studies should be carried out to investigate the effects of HHP treatment on different types of lagers and ales, our results revealed that HHP could be successfully used to increase the shelf life of beer even at temperatures well below those required for heat pasteurization.     

Levels of gliadin in commercial beers

The gliadin contents of twenty-eight commercially available beers spanning the range of grist material and alcohol level were determined using a competitive enzyme immunoassay (RIDASCREEN competitive ELISA kit). The gliadin levels ranged from <3 mg/l for gluten-free beers to 145.8 mg/l for filtered American Pale Wheat beers, with: American light lagers (3.9–12.2 mg/l), alcohol free beer (6.5 mg/l), American lagers (7.1–12.3 mg/l), English Pale Ale (7.3 mg/l), English Brown Ale (8 mg/l), European Pale lager (8.3 mg/l), Scottish Ale (12 mg/l), Low carb American lager (12.1 mg/l), American India Pale Ales (11.8–19.3 mg/l), American Pale Ales (14.6–15.3 mg/l), Czech Pilsner (14.9 mg/l), Sweet Stout (17.1 mg/l), Dry Stout (18.9 mg/l), Oktoberfest/Marzen (21.5 mg/l), Russian Imperial Stout (21.3 mg/l), Kolsch (24.9 mg/l), American Porter (28.5 mg/l), and Dunkelweizen (98.2 mg/l) within this range. Ten of the twenty-eight (34%) beers contained less gluten than the guidelines established by Codex Alimentarius Standard (20 ppm gluten). The calculation of gluten is based on the assumption of a 1:1 ratio between gliadin and glutenin.     

Total hordatine content in different types of beers

Hordatines are phenolic secondary metabolites typical of barley. Hordatines withstand at least moderate processing, and thus they are also found in barley malts and beer. So far, no published data on the hordatine content has been available in beers or different styles of beer. The aim of this study was to produce information on the total hordatine content in beers and statistically compare the hordatine content of different beer types. In the current study, hordatines were analysed in 208 beers by high‐performance liquid chromatography equipped with a diode array detector (HPLC‐DAD). The average total hordatine content of all beer samples was 5.6 ± 3.1 mg L^?1 as p‐coumaric acid equivalents (PCAE), with a minimum values 0 to a maximum value 18.7 mg L^?1 PCAE. The total hordatine content correlated positively to the alcohol content in lagers, ales, stouts and porters, but not in wheat beers. There was no statistically significant difference in hordatine content in different types of beer, excluding the non‐alcoholic group of beers. It is noteworthy that non‐alcoholic beers also contained hordatines. More research would be needed to understand how parameters, such as mashing, should be chosen in order to achieve maximum recovery of hordatines in wort and beer.     

Survey of aflatoxins in beer sold in Canada

Between March 1998 and March 2002, 304 samples of domestic (Canadian) and imported beers from 36 countries were picked up for the determination of aflatoxins B₁, B₂, G₁ and G₂. Twelve samples were positive with aflatoxins greater than the limit of quantitation (LOQ) (aflatoxin B₁, 4.4 ng l^-1; aflatoxin B₂, 3.4 ng l^-1; aflatoxin G₁, 11.2 ng l^-1; and aflatoxin G₂, 6.2 ng l^-1). Five samples from Mexico, two samples from Spain and one from Portugal contained aflatoxin B₁. Four samples from India contained aflatoxins B₁ and B₂. The remaining samples contained less than the LOQ for aflatoxins B₁, B₂, G₁ and G₂. The analytical method for this survey was based on that of Scott and Lawrence (Scott PM, Lawrence GA. 1997. Determination of aflatoxins in beer. Journal of AOAC International 80:1229-1234.). Aflatoxins B₁, B₂, G₁ and G₂ were determined at parts per trillion (ng l^-1) levels in beer by immunoaffinity column cleanup followed by derivatization with trifluoroacetic acid and reversed-phase liquid chromatography with fluorescence detection.     

药食两用类食品中赭曲霉毒素A的高效液相色谱-荧光检测方法

目的:采用免疫亲和净化和高效液相色谱技术,建立淀粉、糖类药食两用食品中赭曲霉毒素A的测定方法。方法:样品粉末经甲醇-水(8:2,V/V)涡旋、超声及振摇提取,提取液以磷酸盐缓冲液稀释后,用商品免疫亲和柱净化,含有赭曲霉毒素A的甲醇洗脱液用高效液相色谱技术分析,C18反相色谱柱分离,荧光检测器测定。结果:赭曲霉毒素A的最低检出浓度为1.0μg/kg(RSN=3);在0.5～100ng/mL范围内,峰面积与质量浓度呈线性关系(r=0.9995);以不含赭曲霉毒素A的太子参、莲子、薏苡、麦冬和龙眼肉为加标基质,加标水平为1～8μg/kg时,平均回收率在81.8%～107%之间,RSD为1.66%～15.0%(n=3)。结论:免疫亲和柱能和高效液相色谱-荧光检测相结合取得较为满意的结果,准确度高、精密度好,满足欧盟对食品饲料中OTA检测方法的要求,适合于淀粉、糖类药食两用食品中赭曲霉毒素A的测定。     

高效液相色谱法检测粮油中黄曲霉毒素方法验证

该文报道验证同时检测粮食、植物油中黄曲霉毒素B1、B2、G1和G2的免疫亲和柱净化-柱后光化学衍生-高效液相色谱方法.样品经甲醇-水(体积比为70∶30)提取,通过免疫亲和柱富集和净化,采用Cloversil C18色谱柱(4.6mm×150 mm,粒度5μm),以甲醇:水(50∶50)溶液为流动相,柱后光化学衍生,利...     

Relationships of Overall Estery Aroma Character in Lagers with Volatile Headspace Congener Concentrations

In lager beers the intensity of “estery” aroma character is regarded as an important component of sensory quality, but its origins are somewhat uncertain. Overall “estery” aroma intensity was predicted from capillary gas chromatographic (GC) data following solid phase micro extraction (SPME) of headspaces. Estery character was scored in 23 commercial lagers using rankrating, allowing assessors (13) constant access to a range of appropriate standards. From univariate data analysis, all assessors behaved similarly and lagers fell into three significantly different groups: low (1), high (1) and intermediate (21). The quantification of 36 flavour volatiles by SPME of headspaces was reproducible and principal component analysis explained 91% total variance. Multiple linear regression could utilise only a restricted (26) set of flavour volatiles, whereas partial least square regression, that considered all flavour components, showed significant differences and improved prediction. However, an artificial neural network that could compensate for non‐linearities and interactions in ester perception gave the most robust prediction at R² = 0.88.     

环丙沙星免疫亲和柱的制备及优化

制备环丙沙星(Cip)抗生素的免疫亲和柱(IAC),研究优化IAC 柱的鉴定和洗脱条件,并测试其最佳性能,最终洗脱液选择4ml 50% 的甲醇,在重复使用5 次后,其柱容量仍能达到开始柱容量的25% 左右,采用高效液相色谱荧光检测器(HPLC-FLD)对IAC 进行回收率测定,以0.05% 的甲酸水溶液- 甲醇体系作为流动相,梯度洗脱HPLC-FLD 方法的线性范围10～1000ng/ml,相关系数大于0.99,测定出IAC 柱对环丙沙星的回收率为74.38%～105.552%。