Optimised quantification of the antiyeast activity of different barley malts towards a lager brewing yeast strain

The brewing of beer involves two major biological systems, namely malted barley (malt) and yeast. Both malt and yeast show natural variation and assessing the impact of differing malts on yeast performance is important in the optimisation of the brewing process. Currently, the brewing industry uses well-established tests to assess malt quality, but these frequently fail to predict malt-associated problem fermentations, such as incomplete fermentations, premature yeast flocculation (PYF) and gushing of the final beer product. Antimicrobial compounds, and in particular antiyeast compounds in malt, may be one of the unknown and unmeasured malt factors leading to problem fermentations. In this study, the adaptation of antimicrobial assays for the determination of antiyeast activity in malt is described. Our adapted assay was able to detect differing antiyeast activities in nine malt samples. For this sample set, malts associated with PYF during fermentation and gushing activity in beer showed high antiyeast activity. Both PYF and gushing are malt quality issues associated with fungal infection of barley in the field which may result in elevated antimicrobial activity in the barley grain. Also, two more malts that passed the normal quality control tests were also observed to have high antiyeast activity and such malts must be considered as suspect. Based on our results, this assay is a useful measure of malt quality as it quantifies the antiyeast activity in malt which may adversely impact on brewery fermentation.     

Chemical composition, in vitro anti-yeast activity and fruit juice preservation potential of lemon grass oil

The anti-yeast activity of lemon grass oil was evaluated against several food spoiling yeasts (Saccharomyces cerevisiae, Zygosaccharomyces bailii, Aureobasidium pullulans, Candida diversa, Pichia fermentans, Pichia kluyveri, Pichia anomala and Hansenula polymorpha) through disc diffusion and microbroth dilution method. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) varied from 0.28 to 1.3 mg/ml and 0.56 to 4.5 mg/ml, respectively, where highest MIC (2.25 mg/ml) was shown by A. pullulans and lowest MIC (0.28 mg/ml) was shown by C. diversa and P. anomala. Kill time assay was conducted for selected three yeast strains where S. cerevisiae showed highest reduction (3 log cfu) in viability within 24 h exposure of lemon grass oil at MFC level. Further, the anti-yeast efficacy of lemon grass oil alone and in combination with thermal treatment was evaluated in real food system i.e. mixed fruit juices. Chemical composition analysis of lemon grass oil by gas chromatography–mass spectrometry (GC–MS) revealed that the dominant compounds were geranial (40.5%), neral (30.7%), geranyl acetate (5.1%), caryophyllene (2.5%). Present results established the superior performance of integrated (thermal–lemon grass oil) treatment over the individual exposure (lemon grass oil or thermal treatment alone) for fruit juice preservation.     

Comparison of beer quality attributes between beers brewed with 100% barley malt and 100% barley raw material

BACKGROUND: Brewing with 100% barley using the Ondea^® Pro exogenous brewing enzyme product was compared to brewing with 100% barley. The use of barley, rather than malt, in the brewing process and the consequences for selected beer quality attributes (foam formation, colloidal stability and filterability, sensory differences, protein content and composition) was considered. RESULTS: The quality attributes of barley, malt, kettle‐full‐wort, cold wort, unfiltered beer and filtered beer were assessed. A particular focus was given to monitoring changes in the barley protein composition during the brewing process and how the exogenous OndeaPro^® enzymes influenced wort protein composition. All analyses were based on standard brewing methods described in ASBC, EBC or MEBAK. To monitor the protein changes two‐dimensional polyacrylamide gel electrophoresis was used. CONCLUSION: It was shown that by brewing beer with 100% barley and an appropriate addition of exogenous Ondea^® Pro enzymes it was possible to efficiently brew beer of a satisfactory quality. The production of beers brewed with 100% barley resulted in good process efficiency (lautering and filtration) and to a final product whose sensory quality was described as light, with little body and mouthfeel, very good foam stability and similar organoleptic qualities compared to conventional malt beer. In spite of the sensory evaluation differences could still be seen in protein content and composition. Copyright © 2011 Society of Chemical Industry     

Quantification of strains in mixed lager yeast cultures using microsatellite PCR and GeXP

Mixed culture fermentation with lager yeast is relatively new in brewing. Maintaining the proportion of strains during fermentation is important to assure the quality of beer and accordingly needs to be monitored. The current discriminatory methods have limited application for lager strains. In the present study, a rapid method to monitor the strain proportion of strains in mixed samples of two different lager yeast strains was developed using microsatellite polymerase chain reaction (PCR) and GeXP Genetic Analysis System. Microsatellite markers in the lager yeast genome were searched using SSR Hunter software. Quantitative PCR using these microsatellite markers was performed and PCR products were analysed by capillary electrophoresis. One locus - mitochondrial carnitine acetyltransferase – was found to discriminate the two strains. A standard curve was generated based on the premixed samples of the two strains enabling the proportion of the stains to be determined. This method is a fast and reliable approach to monitor the strain proportion of mixed lager yeast fermentation. © 2020 The Institute of Brewing & Distilling     

青岛啤酒酵母与高浓酵母筛选高浓酿造酵母融合亲株

以青岛啤酒酵母和高浓精酵母为供试菌株,筛选出生长良好的酵母,为选育具有青岛啤酒风味的高浓酵母做准备.比较了7株酵母不同糖类发酵、离子抗性、二氧化碳减重、发酵液风味品评等指标.结果表明:T1、T2和T3是传统的青岛啤酒发酵菌株,其发酵液口味符合青岛啤酒口味要求,且对Cu2+均不耐受;而G4和G6发酵减重试验和风味物质分析中的乙醛含量指标的评价均优于G5和G7菌株,且它们的发酵液的风味也接近青啤口味.因此,选择T1、T2、T3和G4、G6作100L酿造试验,进一步确定融合亲株.     

Antioxidant composition and activity of barley (Hordeum vulgare) and malt extracts and of isolated phenolic compounds

Phenolics have been identified and quantified in nine varieties of barley and their corresponding malts as flavan-3-ols, flavonols, phenolic acids and apolar esters. Flavan-3-ols are monomers, (+)-catechin and (−)-epicatechin, and polymers constituted mainly by units of (+)-catechin and (+)-gallocatechin. The most abundant compounds were the dimers procyanidin B3 and prodelphinidin B3. The main trimeric procyanidin was procyanidin C2. After malting, the phenolic content decreased for all varieties. Catechin monomers were the most affected. Beside polyphenols, barley and malt extracts contained other antioxidants: carotenoids (lutein and zeaxanthin) and tocopherols (α, δ and γ). The antioxidant activity was measured using three methods: capacity to react with DPPH^. (ARP), inhibition of lipoxygenase activity (LoxI) and inhibition of cooxidation of β-carotene in a linoleate model system (AOP). The inhibition of cooxidation of β-carotene in a linoleate model system did not allow varieties to be discriminated. They all have high antioxidative properties. Using this assay, tocopherols were the best antioxidants. The ARP (antiradical power) was correlated positively with the amount of total flavan-3-ols (r = 0.89) and increased with the degree of polymerisation. The LoxI assay allowed discrimination of the nine varieties of barley and their corresponding malts but was not correlated with any compound, although flavan-3-ols were good inhibitors of lipoxygenase activity. © 1999 Society of Chemical Industry     

青岛啤酒酵母与高浓酵母筛选高浓酿造酵母融合亲株100L发酵分析

以青岛啤酒酵母T1、T2、T3和高浓酵母G4、G6为供试菌株,筛选生长良好的酵母,为筛选具有青岛啤酒风味的高浓酵母原生质体融合亲株做指导。比较了5株酵母菌100L发酵过程中酵母菌数量、双乙酰变化及待滤酒发酵度、酸度、α-氨基氮同化率等指标。结果表明:G4和G6酵母数量变化、双乙酰变化、发酵度和α-氨基氮同化率指标优于T1、T2和T3,青岛啤酒酵母中T1和T3除酵母凝聚性外其他指标都优于T2。因此,确定T1、T3和G4、G6为融合亲株。      

添加不同水果的柑橘果酒酿造与品质分析

为解决柑橘果酒营养功能单一、香气滋味结构欠佳等不足,实验研究了柑橘分别与不同用量苹果、雪梨、猕猴桃果醪混合发酵对酒体品质的影响,考察了黄酮、多酚、V_C和总氨基酸含量等营养成分差异。结果显示,苹果等其它水果的添加对发酵过程总糖降低有一定延缓效应,但对果酒总酸含量有促进作用。与单一柑橘果酒相比,黄酮含量随着苹果用量的增加而显著增加(p<0.05),在苹果最大用量(1:1)酒样中,黄酮含量达到393.43 mg/L。在添加猕猴桃的果酒中V_C含量增加显著(p<0.05),等量柑橘和猕猴桃混酿果酒中V_C含量最高,是柑橘果酒的4.38倍。此外,苹果和猕猴桃的添加对果酒中总氨基酸含量也有一定的促进作用,其中柑橘和苹果1:1用量果酒中总氨基酸含量最高,达到604.11 mg/L,比柑橘果酒高出了9.11%。感官分析结果显示,柑橘猕猴桃2:1的酒样感官品评分值最高,达到81.73分,最低的为单一柑橘果酒(76.73分)。综合各项指标的主成分分析(PCA)结果进一步验证了添加苹果等其它水果对柑橘混酿果酒品质改善和提升方面的显著效果。     

Optimization of alcohol‐free beer production by lager and cachaça yeast strains using response surface methodology

Alcohol‐free beers (AFBs) are an attractive segment of the beer market both for the brewing industry and for consumers. While AFBs produced by arrested/limited fermentation often suffer from a lack of volatile compounds, beer flavour can be improved by yeast selection and optimization of fermentation conditions. The yeast selection strategy was demonstrated by comparing traditional lager yeast with selected cachaça yeast strains. Correspondingly, response surface methodology was used to enhance the formation of the flavour‐active volatile compounds by optimization of the fermentation conditions (original wort extract, fermentation temperature, pitching rate). Statistical analysis of the experimental data revealed the relative significance of process variables and their interactions. The developed quadratic model describing the responses of total esters and higher alcohols to changes in process variables was used to predict the ideal fermentation conditions in terms of flavour formation. The predicted conditions were experimentally verified and alternative strategies of AFB production are suggested. Copyright © 2016 The Institute of Brewing & Distilling     

不同冲泡次数普洱生茶浸出物含量及滋味品质变化分析

采用超高效液相色谱-高分辨质谱联用技术结合茶叶感官审评方法，分析普洱生茶不同冲泡次数茶汤中浸出物的变化和滋味特征。从普洱生茶茶汤中共检出138 种浸出物，主要为氨基酸类、儿茶素及其衍生物、酚酸及其衍生物、黄酮类、生物碱类5 类物质，其对茶汤的主要滋味贡献为鲜味与苦涩味。普洱生茶茶汤的滋味总体评分与苦度、涩度、厚度呈显著正相关，不同冲泡次数下的浸出物总量与滋味总体评分呈显著正相关。浸出物总量及滋味品质均在第2泡时达到最大，后随冲泡次数的增加，浸出物总量不断减少，茶汤滋味逐渐淡薄。本研究围绕普洱生茶冲泡过程中浸出物的变化及其与滋味品质的关系进行分析，有助于揭示云南普洱生茶的耐泡性以及冲泡过程中茶汤滋味的变化特点。     

Rheological properties and stability of low-in-fat dressings prepared with high-pressure homogenized yeast

The aim of present study was to investigate the feasibility of application high-pressure homogenized (HPH) yeast aqueous dispersions with low nucleic acid content for the formulation of low-in-fat dressings. The HPH treatment (1500 bar, 3 passes) in alkaline medium improved the protein dispersibility (>50%). Emulsions were prepared using sunflower oil (12.0% or 25% w/w oil), xhantan/guar gums (0.5% w/w), modified starch (0–4.0% w/w), salt, sucrose, acidulants, EDTA, and antimicrobial agents. All emulsions (pH 3.97 ± 0.27; a_w = 0.97 ± 0.01), whatever the starch content, behaved clearly as pseudoplastic fluids in steady flow measurements. Moreover, as the frequency sweep measurements were made they also exhibited a weak gel behavior. Although the presence of starch produced an increase of mean particle size (D_3,2 values), the rheological parameters (consistency index, proportionality coefficient and coordination number) also increased, so that the starch contributes to reinforce the three-dimensional network formed by oil droplets, protein aggregates and other polysaccharides. Yeast dressings were stable to coalescence after 28 days of quiescent storage (7.0 ± 0.5 °C) and only the highest starch concentration at 25% w/w oil was sufficient to maintain the stability of network.     

Relationship of ergosterol content and fungal contamination and assessment of technological quality of malting barley preserved in a metal silo using the near-ambient method

Environmental microbiologists frequently use ergosterol, a fungal-specific membrane lipid, as an indicator of fungal infection in grain and other plant materials. Microbiological loading and technological quality of barley was determined directly after harvest, after post-harvest drying, and during storage. The conventional plate count method was used to measure fungal contamination (CFU). Ergosterol concentration (ERG) was determined by extraction, saponification and quantification using high-performance liquid chromatography (HPLC) with UV detection. The laboratory malting method was used to determine technological quality of the malt. Results showed a significant correlation between ERG and CFU (the coefficient of correlation was 0.92). Analyses also indicated that the high germinative energy and technological quality of the malt produced from dried barley was retained.     

Phenolic acid analysis and antioxidant activity assessment of oil palm (E. guineensis) fruit extracts

Phenolic compounds in oil palm fruit (E. guineensis) were extracted in soluble free (SFP), insoluble-bound (ISBP) and esterified (EFP) forms. The total phenolic content (TPC) of the oil palm fruit extracts was determined using the Folin–Ciocalteu method and found to range from 5.03 to 9.04 g/L per g of dried weight (DW). The antioxidant activities of oil palm phenolic extracts were analysed using free radical scavenging assays and results showed that oil palm phenolic extracts contained antioxidant activities in the order of ISBP > EFP > SFP. Eight different phenolic acids were identified and quantified using a simple reversed-phase high performance liquid chromatography (HPLC) with a diode array detector (DAD) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). Ferulic, p-hydroxybenzoic and p-coumaric acid were the dominant phenolic acids found in oil palm fruit extracts and ranged from 55 to 376 μg/g of DW.     

Comparison of the impact on the performance of small‐scale mashing with different proportions of unmalted barley,Ondea Pro®, malt and rice

The impact of using different combinations of unmalted barley, Ondea Pro® and barley malt in conjunction with a 35% rice adjunct on mashing performance was examined in a series of small scale mashing trials. The objective was to identify the potential optimal levels and boundaries for the mashing combinations of barley, Ondea Pro®, malt and 35% rice (BOMR) that might apply in commercial brewing. Barley and malt samples used for the trials were selected from a range of Australian commercial barley and malt samples following evaluation by small‐scale mashing. This investigation builds on previous studies in order to adapt the technology to brewing styles common in Asia, where the use of high levels of rice adjunct is common. Mashing with the rice adjunct, combined with differing proportions of barley, Ondea Pro® and malt, resulted in higher extract levels than were observed for reference mashing, using either 100% malt reference or 100% barley reference and Ondea Pro® enzymes. Synergistic mashing effects between barley, Ondea Pro® and malt were observed for mash quality and efficiency parameters, particularly wort fermentability. The optimum levels of barley in the grist (with the relative level of Ondea Pro®) were assessed to be in the range 45–55% when paired with 10–20% malt and 35% rice. When the proportion of malt was reduced below 10% of the grist, substantial reductions in wort quality were observed for wort quality parameters including extract, lautering, fermentability, free amino nitrogen and haze. Extension of this new approach to brewing with rice adjuncts will benefit from further research into barley varietal selection in order to better meet brewer's quality requirements for the finished beer. Copyright © 2016 The Institute of Brewing & Distilling     

Post-harvest assessment of wheat and barley kernel infections with fungi of the genus Fusarium using thermal analysis

The aim of this study was to evaluate the applicability of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for discriminating wheat and barley kernels naturally infected with fungi of the genus Fusarium from healthy kernels. Differences in selected thermal parameters were observed between infected and healthy kernels. In infected wheat kernels, the 2nd endothermic peak occurred at 58.6–62.3 °C, the 3rd endothermic peak at 270.1–279.7 °C; the area under the DSC curve was determined at 1842–2246 J g⁻¹, and mass loss at 76.26–80.39%. In healthy wheat kernels, the above parameters were determined at 77.0–78.9 °C, 292.6–311.0 °C, 1180–1432 J g⁻¹, and 71.10–74.92%, respectively. In infected barley kernels, the 2nd endothermic peak occurred at 51.6–56.4 °C, the 3rd endothermic peak at 286.1–290.1 °C; the area under the DSC curve was determined at 1752–1998 J g⁻¹, and mass loss at 78.65–81.22%. In healthy barley kernels, the investigated parameters were determined at 69.1–74.3 °C, 310.0–324.9 °C, 1187–1249 J g⁻¹, and 72.18–74.09%, respectively.     

Quality assessment of ready-to-eat Pacific saury (Cololabis saira) using microwave-assisted thermal sterilisation combined with olive oil vacuum impregnation

Although microwave-assisted thermal sterilisation (MATS) held great potential to sterilise ready-to-eat (RTE) products compared with traditional retort sterilisation, the quality improvement effect of MATS treatment on shelf-stable RTE products has not been extensively studied. This study was performed to evaluate the efficacy and applicability of MATS combined with olive oil vacuum impregnation against lipid oxidation and microbial growth in RTE Pacific saury during storage. MATS combined with olive oil vacuum impregnation (MTSO) effectively reduced processing time (by 57%) compared to retort-treated RTE Pacific saury at the same thermal lethality value. The lower cooking loss (6.19%) and colour damage indicated that MTSO enhanced water retention and the stability of tissue structure compared to retort-treated group (9.88%) or no olive oil group (7.11%). Lipid oxidation and protein degradation were effectively inhibited in MATS groups compared to retort-treated ones during storage; such effect was more effective in olive oil impregnated group. Likewise, microbial activity and electronic sensory evaluations showed that the shelf life of MTSO group was extended by 1 week compared to retort-treated groups. Overall, MTSO had considerable industrial potential to yield RET Pacific saury and even RTE products with better quality attributes than retort-treated ones.     

Antioxidant and antimicrobial activity of Cynara cardunculus extracts

The whole, fresh involucral bracts of cardoon, Cynara cardunculus L. (Compositae), were extracted with EtOH and an aqueous suspension of the obtained EtOH extract was partitioned successively with CHCl₃, EtOAc and n-BuOH, leaving a residual water extract. All obtained extracts were evaluated for their antioxidant and antimicrobial properties. The antioxidant potential was evaluated using following in vitro methods: FRAP (ferric reducing antioxidant power) assay, and scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. Antimicrobial activity was estimated using a microdilution technique against food-borne, mycotoxin producers and human pathogenic bacteria and micromycetes. The following bacteria were tested: Salmonella typhimurium, Escherichia coli, Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, as well as micromycetes: Aspergillus niger, Aspergillus ochraceus, Aspergillus flavus, Penicillium ochrochloron, Penicillium funiculosum, Trichoderma viride, Fusarium tricinctum and Alternaria alternata. Results showed that all extracts possessed concentration-dependent antioxidant activity. In biological assays, C. cardunculus extracts showed antimicrobial activity comparable with standard antibiotics.     

Determination of tetracyclines in pig and other meat samples using liquid chromatography coupled with diode array and tandem mass spectrometric detectors

Two high performance liquid chromatographic methods (HPLC–DAD and LC–MS/MS) were developed to analyze tetracycline (TC) residues in pig meat (pork) samples. The method involved a sample preparation using a solid–liquid extraction (SLE) by McIlvaine buffer, followed by a solid-phase extraction (SPE) clean-up using Strata-XL cartridges. The developed sample clean-up resulted in a selective chromatogram in the HPLC–DAD separation and a reduced matrix effect (ME) in LC–MS/MS analysis. Moreover, HPLC columns packed with core–shell particles were tested for separation, which further enhanced the sensitivity and the selectivity of determinations. The validation of the methods for pig samples was carried out according to European Union 2002/657/EC decision. In addition, validation was also performed for bovine, chicken, and turkey meat samples using HPLC–DAD method. The performance characteristics of determinations were evaluated with both spiked and incurred samples, and were systematically compared. LC–MS/MS technique was found to be more accurate for spiked samples; however, HPLC–DAD method resulted in more reliable concentrations for incurred samples.     

Quality and antioxidant activity detection of Crataegus leaves using on-line high-performance liquid chromatography with diode array detector coupled to chemiluminescence detection

An on-line high-performance liquid chromatography–diode array detector combined with chemiluminescence detection (HPLC–DAD–CL) method was developed to evaluate the antioxidant activity and quality of Crataegus leaves derived from different species and habitats. The chromatographic fingerprint and active profiles of Crataegus leaves were simultaneously achieved by HPLC–DAD–CL. Main antioxidants in Crataegus leaves were identified by HPLC–DAD–CL and HPLC/ESI/MS. Data analysis based on the total antioxidant activities of 10 batches of samples indicated that there were obvious differences among samples from different species and habitats. Good precision and reproducibility were obtained for DAD and CL detection with relative standard deviations less than 1.0% for retention time and 4.0% for intra and inter-day variations. The results suggested that the on-line method might provide potential information for the identification and quantitation of active markers, which were directly associated with the quality of herbal medicines.