Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693?×?10^?2 and 1.397?×?10^–2?min^?1 for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79–84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p?<?0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.     

Occurrence of biogenic amines in beers produced with malted organic Emmer wheat (Triticum dicoccum)

Because several groups of microorganisms are able to decarboxylate amino acids, the presence of biogenic amines (BA) can be seen as an index of the microbiological quality of the brewing process. BAs were quantified for the first time in the intermediate products and craft beers produced with malted organic Emmer wheat (Triticum dicoccum) in a small size brewery in order to assess the possible presence of critical control points related to biological hazard in the brewing process. BA levels in beers produced exclusively from malted organic Emmer wheat were between 15.4 and 25.2 mg l^–1 in the samples of light beer (Lt) and between 8.9 and 15.3 mg l^–1 in double malt beers (DM) ready for consumption (the beers stored for 90 days at 1–2°C). Cadaverine and tyramine were the main BAs in the Lt and DM beers, respectively. Increased concentrations of BAs seemed to be more related to the heat treatment of the processing product during mashing and wort boiling, rather than to the fermentation process. Much lower concentrations were found in finished beers obtained from 50% malted organic Emmer wheat and 50% malted barley (up to 3.2 mg l^–1) or from 30% malted Emmer wheat (up to 8.3 mg l^–1). Thus, Emmer wheat malt can be a useful alternative to wheat and spelt for the production of beer with a limited content of BA, if the processing technology is kept under control.     

细菌污染对啤酒的影响

概述了重要细菌群的特征 ,及其初始和二级代谢终产物对啤酒香味风味的影响 ,提出了针对主要污染菌在生产过程中应采取的有效微生物控制和卫生措施     

HPLC法检测纯生啤酒蔗糖转化酶活性的研究

本试验采用HPLC法对纯生啤酒中蔗糖转化酶活性进行了定量分析。对市售不同品牌8度纯生啤酒的蔗糖转化酶活性进行了连续四个月的检测,市场上三个月货架期的纯生啤酒蔗糖转化酶活性水平有较大差异,最低0．24×10^-4,最高1．68×10^-4U。同时进行了温瓶试验,并实际取样评价了生产上温瓶工艺对蔗糖转化酶活性的影响。温瓶工艺对蔗糖转化酶活性影响较大,是蔗糖转化酶活力降低的关键因素。并进行了消费周期对蔗糖转化酶活性的影响研究,蔗糖转化酶的活性随着消费周期的延长逐渐降低。     

HPLC法测定啤酒中嘌呤含量的方法研究

对某知名品牌啤酒中的嘌呤含量进行了测定。通过高效液相色谱分析技术,确定了水解条件以及色谱分离条件。研究结果表明,该品牌啤酒中腺嘌呤、鸟嘌呤、黄嘌呤和次黄嘌呤的含量分别为0．01724mg／mL、0．30968mg／mL、0.01806mg／mL、0．005092mg／mL,水解条件为：三氟乙酸与甲酸（1：1）混合液在100℃下水解1．0h。     

高效液相色谱在啤酒检测中的应用

高效液相色谱法（HPLC）已成为应用极为广泛的化学分离分析的重要手段。本文主要介绍了高效液相色谱法（HPLC）原理、维护以及在啤酒检测中的应用。     

HPLC与苯胺法测定啤酒中木聚糖的研究

研究了高效液相色谱法和苯胺法测定啤酒中的木聚糖。色谱法和苯胺法检测啤酒中的木聚糖加标回收率分别为93.36%和87.85%,相对标准偏差RSD值为1.73%和2.46%。结果显示液相色谱法可以准确分析啤酒中木聚糖的含量,优于苯胺比色法。     

啤酒中脱氧雪腐镰刀菌烯醇含量的测定

采用高效液相色谱法对啤酒中脱氧雪腐镰刀菌烯醇(DON)进行分析检测。选用色谱柱Zorbax Eclipose XDB-C18(4.6mm×250mm,5μm),流动相为甲醇-0.05%磷酸水溶液(体积比20∶80),柱温30℃,流速1.0mL/min,检测波长210nm。在此条件下,DON得到很好分离,在0.75～100mg/L范围内线性关系良好,R2=0.999 3,外加标回收率在85.36%～96.92%之间,RSD为4.21%,该方法可以简便、准确地测定啤酒中DON含量。     

Dietary acrylamide exposure among Finnish adults and children: the potential effect of reduction measures

A deterministic exposure assessment using the Nusser method that adjusts for within-subject variation and for nuisance effects among Finnish children and adults was carried out. The food consumption data covered 2038 adults (25–74 years old) and 1514 children of 1, 3 and 6 years of age, with the data on foods’ acrylamide content obtained from published Finnish studies. We found that acrylamide exposure was highest among the 3-year-old children (median?=?1.01?µg?kg^?1?bw^?day^?1, 97.5th percentile?=?1.95?µg?kg^?1?bw^?day^?1) and lowest among 65–74-year-old women (median?=?0.31?µg?kg^?1?bw^?day^?1, 97.5th percentile?=?0.69?µg?kg^?1?bw^?day^?1). Among adults, the most important source of acrylamide exposure was coffee, followed by casseroles rich in starch, then rye bread. Among children, the most important sources were casseroles rich in starch and then biscuits and, finally, chips and other fried potatoes. Replacing lightly roasted coffee with dark-roasted, swapping sweet wheat buns for biscuits, and decreasing the acrylamide content of starch-based casseroles and rye bread by 50% would result in a 50% decrease in acrylamide exposure in adults. Among children, substituting boiled potatoes for chips and other friend potatoes and replacing biscuits with sweet wheat buns while lowering the acrylamide content of starch-based casseroles by 50% would lead to acrylamide exposure that is only half of the original exposure. In conclusions, dietary modifications could have a large impact in decreasing acrylamide exposure.     

温度和氧对啤酒老化的影响

研究了4℃、20℃和38℃三种温度条件下,不同溶解氧含量的啤酒其老化物质和香气成分的变化。贮存6个月后有关风味稳定性指标结果如下:贮存温度升高时5-羟甲基糠醛(5HMF)含量显著增加,从20℃到38℃增加了244%,氧含量对5HMF影响很小。TBN变化与5HMF相似,但不如5HMF敏感,从20℃到38℃只增加了5.3%。色度随着氧和贮存温度的增加而增加,38℃贮存的溶氧高的啤酒比4℃对照啤酒色度增加了3.18EBC。DPPH还原力随着贮存温度的升高而下降。贮存期间,对主要挥发性香气的跟踪分析表明,双乙酰在贮存过程持续增加,溶氧高的啤酒其含量更高,贮存2个月后,含量达到其风味阈值,导致啤酒产生“双乙酰”味。乙酸乙酯和乙酸异戊酯在贮存过程含量下降,38℃贮存6个月后,2种酯含量比4℃对照分别降低了18%和21%,溶氧高的啤酒降低程度更大,将会影响啤酒的香气。因此,减少成品啤酒的溶解氧含量,降低贮存温度,可以提高啤酒的抗老化能力。     

保健燕麦茶啤酒的工艺研究

阐述了保健燕麦茶啤酒的生产工艺流程及生产工艺要点,采用大麦芽60%,燕麦20%,糖浆20%的原料配比,并在85℃对茶水比为1:180进行20min的绿茶浸提,生产过程中浸提后茶汁添加量为5%,酒花添加量0.02%,添加时间初沸后20min。经过中试生产,保健型燕麦茶啤酒各项指标均符合GB。     

ANALYSIS OF BEER CARBONYLS AT THE PART PER BILLION LEVEL BY COMBINED LIQUID CHROMATOGRAPHY AND HIGH PRESSURE LIQUID CHROMATOGRAPHY

Carbonyl compounds have been isolated from lager by low pressure distillation and recovered from the distillate as their 2,4-dinitrophenylhydrazone derivatives. The derivatives were subsequently separated into four monocarbonyl classes on a magnesia-silica gel column, and then each class resolved by HPLC. This technique has proved to be sensitive to carbonyls in lager at concentrations below 0·1 ppb and shows a high degree of resolution. So far, twelve methyl ketones, eleven saturated aldehydes and eight alkenals have been separated. The content of both fresh and aged lagers has been examined and changes in concentration discussed in relation to their reported taste thresholds.     

调味品中罗丹明B的HPLC-FLD-DAD测定方法研究

建立了高效液相色谱(HPLC)-荧光检测器(FLD)-二极管阵列检测器(DAD)测定调味品中罗丹明B的方法.不同基质样品采用适宜的提取液提取后,以甲醇和0.02 mol/L的乙酸铵溶液(70 ∶ 30)为流动相,经C18色谱柱分离,用荧光-二极管阵列检测器串联测定,FLD激发波长为547 nm,发射波长为573 nm,DAD检测波长为550 nm,外标法定量.实验结果表明:罗丹明B用FLD检测在1～2000 ng/mL浓度范围内呈良好的线性关系,定量限为0.005 mg/kg;DAD检测在100～2000 ng/mL浓度范围内呈良好的线性关系,定量限为0.5 mg/kg.方法回收率在83.1％～105.1％之间,RSD为1.64％～5.42％(n=6).该方法准确、灵敏,前处理简单,适用于调味品中罗丹明B的定性、定量分析.     

Analysis of Aldehyde-bisulfites in Beer by HPLC-Fluorescence Detection with Post-column Derivatization

An analytical method was based on the aldehyde-bisulfite (separated by HPLC) reaction with o-phthalaldehyde in the presence of ammonium acetate, producing a fluorescent compound. Detection limits of alkanalbisulfite (from formaldehyde- to octylaldehyde-bisulfite) and 2-alkenalbisulfite (from trans-2-hexenal- to trans-2-nonenal-bisulfite) ranged from 5 nM to 25 nM. The method was less sensitive for free sulfite (detection limit 100 μM) than for aldehyde-bisulfite. Increasing acetaldehyde-bisulfite with addition of 25 mM acetaldehyde to a beer sample showed free sulfite in the beer. Free sulfite and acetaldehyde-bisulfite were detected in commercial beers but other aldehyde-bisulfites were not.