酒花香气成分的检测及富含典型酒花香气啤酒的试验研究

单萜类物质是贡献啤酒酒花香气的重要成分。本研究在100L中试规模,原麦汁浓度为14°P,苦味质为20BU的条件下,从不同酒花添加工艺、添加量和品种三方面分析了啤酒中8种单萜类酒花香气物质的含量,并进行感官品评,发现在发酵罐中添加l％o香花的效果最好,啤酒风格因酒花品种不同而有异。8种酒花香气物质中里那醇、香叶醇、口．香茅醇和α-萜品醇最为重要,其啤酒中的含量与酒花中里那醇和香叶醇含量密切相关,前三者与前人研究-致,但本研究发现“α-萜品醇”也是重要香气物质之-。但啤酒中的酒花香气物质含量高,酒花香味不-定强,这可能与其构型有关,因此,又研究了三种酒花在啤酒酿造过程中酒花香气物质的同分异构体,包括（R）-（-）-里那醇、（S）-（＋）-里那醇、（-）-α-萜品醇、（十）-α-萜品醇、（R]-（＋）-卢-香茅醇、（S）-（-）-卢-香茅醇的含量。研究发现酒花品种的差异会引起同分异构体含量及比例的显著差异,加上其阈值的变化。进-步验证了同分异构体对啤酒中酒花香味的影响。     

酒花萜烯醇及其立体异构体在啤酒酿造中的检测及其变化研究

采用顶空固相微萃取-气相色谱质谱技术(HS-SPME/GC-MS),跟踪检测了啤酒酿造过程中(R)-(-)-里那醇、S-(+)-里那醇、(R)-(+)-β-香茅醇、(S)-(-)-β-香茅醇、(+)-α-萜品醇、(-)-α-萜品醇、香叶醇、橙花叔醇等12种香气化合物。通过控制酿造过程中不同的香花添加工艺,发现在煮沸结束、回旋沉淀槽及主酵结束后添加香花工艺较煮沸结束前10 min添加工艺,能显著提高萜烯醇及其立体异构体保留在啤酒中的含量,其中对酒花香气具有重要贡献的四种萜烯醇:R-(-)-里那醇、香叶醇、R-(+)-β-香茅醇及橙花叔醇在啤酒中的含量范围分别为1.94¹4.39μg/L、9.8314.39μg/L、9.83¹2.10μg/L、2.9112.10μg/L、2.91⁶.79μg/L、5.346.79μg/L、5.34⁶.81μg/L,它们的风味强度OAV值范围在0.296.81μg/L,它们的风味强度OAV值范围在0.29⁶.54,并对上述4种物质在啤酒发酵过程中的变化规律展开了进一步探究。结合感官评品结果显示,发现回旋沉淀槽添加香花工艺最好,主酵结束后添加香花工艺次之。     

采用手性色谱柱对啤酒中12种酒花香气及异构体的分析研究

为研究啤酒中酒花香气,采用单一手性色谱柱结合实验室现有的四级杆气质联用仪,建立了12种酒花香气成分及立体异构体的分析方法。色谱柱类型为:RESTEK Rt?-βDEXsa手性色谱柱。样品在45℃的水浴温度下,以550 r/min搅拌并萃取40 min后,取出手柄,直接进样,并解析5 min。采用标准加入法定量,相关系数为0.9900~0.9993;精密度2.26%~11.35%;检出限0.21~1.18μg/L;回收率81.10%~118.70%,表明该法准确可靠。研究检测了国内6种知名啤酒中酒花香气及立体异构体,其与富含典型酒花香气的国外2种啤酒存在着明显的分布差异。其中R-(-)-里那醇占里那醇总含量的55.47%~70.07%,S-(+)-里那醇占29.93%~44.53%;香叶醇含量差异也非常显著;β-香茅醇和α-萜品醇二者有85%及以上的比例都是以(+)形式存在。     

酒花香气物质检测方法的建立及评估

本文主要建立及评估了酒花油和啤酒中酒花香气的检测方法。采用蒸馏法-气相色谱仪测定酒花油中香气组分,酒花样品采用酒花蒸馏装置蒸馏后,将酒花油共定量了香叶烯、里那醇、香叶醇、石竹烯、草烯5种酒花香气组分;为检测值更为准确,采用多点校正内标法定量,内标物为十四烷,所得曲线的相关系数均大于0.995,5种酒花香气组分的RSD值在4.34%-9.45%之间,而回收率在87.50%-111.95%之间。本文另采用顶空固相微萃取-气质联用法测定啤酒中酒花香气组分,啤酒样品采用85μm PA萃取头萃取,在45℃水浴保温45min,共定量了里那醇、香茅醇、香叶醇、香叶酸甲酯、乙酸香茅酯、乙酸香叶酯、反式橙花叔醇等7种酒花香气组分,为减少基体干扰,采用啤酒为基体建立标准曲线,所得曲线的相关系数均大于0.995,7种酒花香气组分的RSD值在4.63%-9.82%之间,而回收率在80.63%-119.38%之间。在以上两种检测方法的基础上,检测了20种酒花和38种啤酒的酒花香气,发现不同品种其酒花香气含量差异较大。     

酒花内生菌转化β-月桂烯合成芳樟醇和香叶醇

利用微生物催化酒花油中β-月桂烯生成芳樟醇和香叶醇是一种理想的生物转化途径,有利于提升酒花β-月桂烯的经济价值。该文从酒花雌花果中筛选出一株内生菌Z1,通过菌落形态观察、生理生化以及16S rDNA序列分析鉴定该菌株;研究其催化β-月桂烯合成芳樟醇和香叶醇的条件,并用于转化酒花油的β-月桂烯。结果表明,酒花内生菌Z1与菠萝泛菌（Pantoea ananatis）的菌落形态和生理生化特点相同,16S rDNA的同源性为98.2%,命名为Pantoea ananatis Z1。将该菌株于葡萄糖蛋白胨酵母麦芽粉（glucose peotone yeast and malt,GPYM）培养基中培养,转化14.1 g/L的β-月桂烯,产物芳樟醇和香叶醇浓度分别为0.89 mg/L和1.09 mg/L。对含有1.41 g/L β-月桂烯的酒花油进行转化,芳樟醇和香叶醇生成量达0.52 g/L和0.09 g/L,转化率分别提高了10 248倍和1 483倍。研究表明,P.ananatis Z1可将酒花油中的β-月桂烯一次性转化为芳樟醇和香叶醇,初步分析认为酒花油中β-月桂烯和芳樟醇的共同存在促进P.ananatis Z1对β-月桂烯转化。     

啤酒中酒花香组分分析方法的研究及其在啤酒酒花香气质量评定中的应用

采用顶空固相微萃取-GC／MS技术，建立了啤酒中酒花香组分的分析方法，可以准确测定里哪醇、β-香茅醇、α-萜品醇、香叶醇、反式-橙花叔醇、乙酸香茅酯、香叶酸甲酯、乙酸香叶酯等8种酒花香组分。应用本方法测定了市售不同品牌啤酒的酒花香组分含量，通过统计分析并结合感官评定，评价了不同品牌啤酒的酒花香质量，本方法的建立有助于啤酒酒花香的量化评定。     

顶空固相微萃取-气相色谱-氢火焰离子化法检测啤酒中的酒化香气成分

来自酒花的微量香气成分会影响啤酒的感官评价和质量。为评价酒花香气对啤酒的影响,本文采用顶空固相微萃取（Hs—SPME）对啤酒前处理后,使用常见且低成本维护的气相色谱一氢火焰离子化法fGC—FID）进行定性定量。以2一壬醇为内标,测定出里那醇、乙酸香茅酯、仪一萜品醇、B一香茅醇、香叶醇5种酒花香气成分。此法的精密度为4．69％～13．41％,回收率为74．95％～106．09％,检出限为0．005～O．028μg·L-1。通过此法进行啤酒检测,结果显示：啤酒中这5种酒花香气含量均〈10μg·L-1,大部分在0．10～5．00μg·L-1之间。研究表明：该法测定准确可靠;与已有方法如顶空固相微萃取一气质联用法（HS—SPME—GC—Ms）相比,该法的仪器常见,维护成本更低,更适合啤酒厂推广使用。     

酒花中萜烯醇类化合物的研究进展

酒酒花添加可赋予啤酒特有的风味,使酒体丰满协调。萜类物质对酒花风味的贡献发挥着重要作用。其中,萜烯醇类物质（如里那醇、香叶醇、β-香茅醇、α-萜品醇、橙花醇等）是影响酒花香气的关键性成分,其在发酵过程中含量的微小变化对啤酒的品质及感官评价影响很大。啤酒中的萜烯醇类物质不仅与酒花品种有关,还与发酵过程中的生物转化有关,甚至在储存时期也有变化。了解酒花中的萜烯醇类香气化合物在啤酒酿造过程中的含量及变化规律与控制和稳定啤酒的风味质量密切相关。该文就酒花中萜烯醇类物质的国内外研究现状做一综述。     

玫瑰深加工产品关键香气成分的分析

采用顶空固相微萃取-气质联用定量与闻香仪相结合的方法,对包括细胞液、玫瑰纯露与玫瑰饮料在内的3种玫瑰深加工产品的关键香气成分进行了分析研究,并结合香气值理论,确定了玫瑰细胞液的关键香气成分为β-苯乙醇、香茅醇、香叶醇和丁子香酚;决定玫瑰纯露质量的主要风味化合物包括:β-苯乙醇、香茅醇、香叶醇、丁子香酚、芳樟醇和玫瑰醚;玫瑰饮料中4种主要呈香化合物分别为:β-苯乙醇、丁子香酚、香茅醇和芳樟醇。     

顶空固相微萃取-气相色谱-质谱法分析啤酒的酒花香组分

采用顶空固相微萃取-GC/MS技术,建立了啤酒中酒花香组分的分析方法。啤酒样品采用PA萃取头,在40℃萃取30 min后直接进行GC/MS分析,鉴定了含量在μg/L量级的里哪醇、β-香茅醇、α-萜品醇、香叶醇、反式-橙花叔醇、乙酸香茅酯、香叶酸甲酯、乙酸香叶酯等8种酒花香组分,随后又以选择离子监测模式(SIM)并以萜品烯-4-酵为内标,实现了定量测定。样品重复测定的相对标准偏差为1.6%～14.9%,回收率为70.4%～128.6%。应用该方法测定了市售的7种啤酒中上述酒花香组分的含量。     

The Contribution of Geraniol Metabolism to the Citrus Flavour of Beer: Synergy of Geraniol and β‐Citronellol Under Coexistence with Excess Linalool

The behaviour of hop‐derived monoterpene alcohols during fermentation by lager yeast was previously investigated in this laboratory. It was suggested that the concentration of geraniol and β‐citronellol in the finished beer increased depending on the initial concentration of geraniol in the wort. In addition, an additive effect among linalool, geraniol and β‐citronellol was found and 5 ug/L of geraniol and β‐citronellol was enough for this effect. In this paper, conditions regarding the enrichment of the initial concentration of geraniol in the wort were investigated. From the screening of various hop cultivars, Citra hop was selected as a geraniol‐rich cultivar. In addition, it was observed that coriander seed, which can be used in beer production as a flavourant, contained not only linalool but also geraniol at high levels. The use of Citra hop or coriander seed was effective for enriching the concentration of geraniol and β‐citronellol in the finished beers. In the Citra beer and in the coriander beer, the content of linalool was excess in comparison with the content of geraniol and β‐citronellol. Therefore, the synergy of geraniol and β‐citronellol, under coexistence of excess linalool, was examined. It was found that the flavour impression of excess linalool became more fruity and citrus by coexistence with geraniol and β‐citronellol and that the coexistence of all three monoterpene alcohols was effective for this synergy. The flavour characteristics of the Citra and coriander beer and the importance of geraniol metabolism for a citrus flavour in beer are discussed.     

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。     

青稞精酿啤酒酿造工艺优化

以大麦芽、青稞为原料，制备青稞精酿啤酒，以感官评分为响应值，通过单因素试验和响应面法对青稞精酿啤酒酿造工艺进行优化，并对青稞精酿啤酒的基本指标和生物活性物质进行分析。结果表明，青稞精酿啤酒的最佳酿造工艺条件为：酒花添加量2 g/L，初始麦汁浓度14 °P，主发酵温度12 ℃。在此优化条件下，青稞精酿啤酒的感官评分为86.7分，外观鲜亮金黄，泡沫细腻，香气丰富，杀口力强。青稞精酿啤酒的酒精度为5.28%vol，β-葡聚糖、总黄酮和γ-氨基丁酸含量分别为（124.26±9.74）mg/L、（138.65±2.07）mg/L和（81.79±6.37）mg/L。     

Biotransformation of monoterpene alcohols by Saccharomyces cerevisiae, Torulaspora delbrueckii and Kluyveromyces lactis

Monoterpenoids are important flavour compounds produced by many plant species, including grapes (Vitis vinifera) and hops (Humulus lupulus). Biotransformation reactions involving monoterpenoids have been characterized in filamentous fungi, but few examples have been observed in yeasts. As monoterpenoids are in contact with yeasts during beer and wine production, biotransformation reactions may occur during the fermentation of these beverages. This paper describes the biotransformation of monoterpene alcohols, of significance in the alcoholic beverage industries, by three yeast species. All three species analysed had the ability to convert monoterpenoids. Saccharomyces cerevisiae and Kluyveromyces lactis reduced geraniol into citronellol, whilst all three yeasts produced linalool from both geraniol and nerol. Monocyclic alpha-terpineol was formed from both linalool and nerol, by all three yeasts. alpha-Terpineol was then converted into the diol cis-terpin hydrate. K. lactis and Torulaspora delbrueckii also had the ability to form geraniol from nerol. Finally, the stereospecificity of terpenoid formation was analysed. Both (+) and (-) enantiomers of linalool and alpha-terpineol were formed in roughly equal quantities, from either geraniol or nerol.     

RAPID GAS CHROMATOGRAPHIC EXAMINATION OF BEER FLAVOUR

Gas chromatographic analysis of the headspace vapour of beer permits rapid measurement of the concentration of myrcene and the principal volatile alcohols, esters and carbonyl compounds in beer. In some cases the results obtained can be correlated with differences in flavour associated with changes in brewing procedure. The strength of the hop aroma of beers which had been dry-hopped, or to which hop oil had been added, was broadly reflected by the content of myrcene, which varied from 7 to 120 μg. per litre. A similar range was found in wort, the content depending on the conditions of boiling. However, the major part of this was lost during fermentation.     

Biotransformation of hop derived compounds by Brettanomyces yeast strains

Several hop derived compounds in wort are known to be converted by yeast during fermentation, influencing the overall perception of the beer. A deeper understanding of such metabolic processes during fermentation is needed to achieve better control of the outcome. Here, the interaction between hop derived compounds and the yeast genera Brettanomyces was studied. Several Brettanomyces strains with different genomic backgrounds were selected, focusing on two traits: beta-glucosidase activity and nitrate assimilation. The role of three beta-glucosidases present in Brettanomyces bruxellensis and Brettanomyces anomalus and their impact on the final monoterpene alcohol profile was analysed. The beta-glucosidase activity was highly strain dependent, with B. anomalus CRL-49 exhibiting the highest conversion. Such activity could not be related to the release of aglycones from hops during fermentation, as a substantial part of such activity was intracellular. Nevertheless, the reduction of geraniol to β-citronellol was remarkably efficient for all Brettanomyces strains during fermentation, and it is suggested that two oxidoreductases BbHye2 and BbHye3 may have an influence. Moreover, the transfer of nitrate from hops to wort and its further assimilation by Brettanomyces species was analysed. The amount of nitrate in wort proved to be linearly proportional to the contact time of the hops with the wort. The level of nitrate assimilation by yeast was shown to be dependent on the nitrate assimilation cluster (YNR, YNI, YNT). Hence, the desired yeast strains may be selected according to the genetic make-up. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling