Hop maturation and resin formation. Effects of extended harvestings on subsequent hop crops

Commercial harvestings of hops (Humulus lupuhlus L, var., Pride of Ringwood) were conducted over a 5 week period encompassing normal harvest time. The effect on yield and α-acid content of the crop was determined, as was the effect on the subsequent crop. Although the yields of hops and α-acid from the first crop were found to plateau for at least 4 weeks, beginning 2 weeks prior to normal harvest, the time of harvesting exercised a significant effect on the yield for the following season. The magnitude of the effect was generally found to correlate with the length of time between training and harvesting of the initial crop, i.e. the shorter the time, the lower the yield of the subsequent crop.     

Cellulose xanthate as a soil conditioner: Field trials

The soil conditioning effects of cellulose xanthate were investigated in eight field trials conducted at widely distributed sites, which were chosen for their records of depressed seedling emergence caused by soil capping. At those sites where weather conditions produced a cap strong enough to reduce seedling emergence, cellulose xanthate, as a 1% aqueous solution applied at 22 kg cellulose ha^?1, prevented capping and improved emergence. At other sites, where caps developed only after emergence, cellulose xanthate also prevented capping and increased the water stability of soil aggregates on the treated plots. The material had no depressive effect on growth of any of the crops (lettuce, onions, carrots, leeks, sugar beet), nor was there any interaction with herbicides. Tasting trials failed to detect any taint in lettuce or parsnips grown on treated plots.     

酒花多酚-潜在的啤酒风味和风味稳定物质

从CO2萃取后的废酒花中获得的多酚提取物，可以在啤酒生产中评价它们的抗氧化力和潜在的风味特征。由LC-MS和LC-UV的分析数据可知获得的多酚提取物具有较高的选择性，且含有所有的多酚物质。采用固相萃取技术，提取的总多酚物质可以进一步被分级为原花青素、黄酮苷和异戊烯基黄酮。除原花青素外，所有多酚溶液都有很强的风味活性且对口感有利。在啤酒酿造过程中添加这些多酚提取物可以明显延长啤酒的风味稳定性？这些新的酒花制品能赋予啤酒独特的风味并提高啤酒的风味稳定性。     

啤酒腐败细菌与酒花抗性

啤酒的腐败细菌有革兰氏阳性菌（乳酸菌、片球菌、M．kristinae等）和革兰氏阴性菌（Pectinatus、巨型球菌、Z．raffinosivorans等）。啤酒中的酒花具有抑制腐败菌的作用，主要物质为异α-酸；酒花能对微生物体内的酶起药物钝化、改变目的底物、抑制药物流入等作用。对啤酒腐败菌的检测方法有聚合酶链式反应（PCR）、伏安型生物传感器检测鉴定微生物细胞、自动微生物检测系统（AMS）、改良MRS培养基检测啤酒中乳酸茵和ATP法。（孙悟）     

Oak barrel maturation vs. micro-oxygenation: Effect on the formation of anthocyanin-derived pigments and wine colour

The objective of this study was to check whether micro-oxygenation (MO) could mimic oak barrel ageing as regard the effect on wine colour. A red wine was submitted to micro-oxygenation for three months while another lot from the same wine was matured in oak barrels for three or six months. After these times, oak-matured and micro-oxygenated wines were bottled and analyzed six months later. The chromatic characteristics of these wines were also compared with those of a control wine that remained in a stainless steel tank all the time. Anthocyanins and anthocyanin-derived compounds were studied by LC–ESI-MS. Monomeric anthocyanins and other compounds including direct anthocyanin–flavanol adducts, ethyl-linked anthocyanin–flavanol compounds, and pyranoanthocyanins were detected. The application of MO for three months produced wines with a lower concentration of monomeric anthocyanins and a higher concentration of vitisin-related pigments than the control wine, the oak mature wines showing similar results than MO wines when aged for the same period of time. Differences were also observed in the chromatic characteristics, the micro-oxygenated and the oak matured wines showing a higher colour intensity than control wine. However, after six months in bottle differences were found between the micro-oxygenated wines and oak matured wines, the latter showing a more stable colour, probably due to the beneficial effects of compounds extracted from the wood (e.g. ellagitannins or wood aldehydes).     

Antioxidant Characteristics of Hops and Hop Products

The method based on the reaction of stable DPPH radical proved to be the best for the determination of antioxidant characteristics of hops and hop products. Antioxidant activity is expressed as the rate of decline in absorbance of the reaction environment and assessed in relative percents. Differences in the values of antioxidant activity were determined in Czech and foreign hop varieties. The highest antioxidant activities in the scope of 70 to 80% rel. were measured in Saaz and Spalter Select. Antioxidant activity in most of the varieties moved in the scope of 40 to 60% rel. A part of antioxidant activity of hops is irreversibly lost in the course of drying. The loss does not usually exceed 5% of the original RA_DPPH value. Drying also resulted in a decrease of polyphenol compound contents. Drying in belt and chamber kilns is comparable from the point of view of preserving hop antioxidant properties. Results of determination of antioxidant activity in hot water extracts of raw hops and ground hops were comparable and statistically non‐significant. The same held true for pelletizing of ground hops. The antioxidant activity of raw hops declined in the course of long‐term storage in dependence on storage temperature. Storage temperature had no effect on the antioxidant activity of the hop pellets packed in a multi‐layer foil without air access.     

Ochratoxin A occurrence and formation in Portuguese wine grapes at various stages of maturation

A total of 93 Portuguese grape samples destined for wine production were examined for the presence of ochratoxin A (OTA) and the OTA producing fungi Aspergillus carbonarius and A. niger aggregate. Samples came from 11 vineyards from four winemaking regions in the North and South of the Portuguese mainland, during the harvest seasons of 2001, 2002 and 2003. Grapes were examined at 3 maturation stages, from setting to the harvesting period, to evaluate when contamination with OTA producing fungi and OTA synthesis occur. The detection of fungi in grape samples was made by plating methods with and without surface disinfection. OTA was formed by 14% of the 650 isolates tested. Most of the OTA producing strains (96%) were isolated at harvest time. At this stage, the percentage of grape samples with OTA producing strains detected without surface disinfection was 56%. With surface disinfection, A. carbonarius was isolated from 10% of the samples. OTA was detected in grapes at the 3 maturation stages. The average OTA concentrations in 60 samples at pea berry (28 samples), early veraison (22 samples) and ripe berry (20 samples) were 263, 149 and 35 ng/kg, respectively. Experiments with an A. carbonarius strain demonstrated that OTA production differs significantly with the composition of the berries at different maturation stages (P<0.001), with a mean value of OTA production at pea berry, early veraison and ripe berry of 3402, 1530 and 22 mug/kg, respectively. The production of OTA by A. carbonarius was correlated positively and negatively with the total acidity of grapes (r(s)=0.855, P<0.001) and reducing sugars content (r(s)=-0.835, P<0.001), respectively. Our data demonstrate that OTA synthesis in grapes occurs since early maturation stages.     

Influence of bunch maturation and chemical precursors on acrylamide formation in starchy banana chips

The present study investigated the effect of ripening stages and chemical precursors on acrylamide formation in deep-fried chips of five plantains and one cooking banana. The highest level of acrylamide was found in the cooking banana, followed by False Horn plantain and French plantain, respectively. French plantain hybrids exhibited a significantly lower (P < 0.05) level of acrylamide when compared to French plantain. The ripening stage demonstrated a positive Pearson correlation (P < 0.05, r = 0.57) with acrylamide formation. As ripening progressed, the levels of glucose and fructose significantly increased (P < 0.05) and showed a positive correlation with acrylamide formation (r = 0.85 and 0.96, respectively). The level of the amino acid asparagine during ripening was not correlated with acrylamide formation. In contrast, the level of histidine, arginine, iso-leucine and cystine during ripening was positively correlated (P < 0.05, r > 0.60) with acrylamide formation in fried chips. The higher level of TP was significantly related (P < 0.05) to the lower level of acrylamide (r = −0.62). The reduced levels of carotenoid isomers, except lutein, during fruit ripening were positively correlated (P < 0.05) with acrylamide formation, especially trans-BC (r = 0.72) and 9-cis-BC(r = 0.64).     

Field trials to control insect pests of farm-stored maize in Zambia

Severe infestations of Sitophilus zeamais Motsch and Sitotroga cerealella Oliv. occur in maize cobs stored under farm conditions in Zambia causing up to 92% damaged grains 8 months after harvest. Shelling the maize reduced S. cerealella damage to low levels and also stabilized the moisture content of the grain providing a more suitable substrate for insecticide application and c control of S. zeamais. Malathion at 12 ppm a.i., tetrachlorvinphos (12 ppm), and jodfenphos (12 ppm), applied as dust admixtures to shelled maize in traditional mud-walled, timber and thatch storage cribs, all kept damaged grains below 10% up to 10 months after harvest. Pirimiphos-methyl (4 ppm) and fenitrothion (2 ppm) maintained these low damage levels up to 8 months after harvest, but there was evidence of continued S. cerealella infestation with these two insecticides.     

RAPD和STS分子标记技术鉴定酒花品种和纯度

运用 DNA 片断的多态性分析判定酒花品种指纹,以5个随机引物成功鉴定了11个常用酒花品种,包括4个香花,5个苦花,青岛大花和 Cluster。Kirin一段多态的随机扩增多态性 DNA(RAPD)片段被转化成序列标记位点(STS),STS 扩增可以检测到青岛大花中5%的麒麟丰禄混合率。     

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。     

酒花多酚对高脂血症小鼠的降脂与抗氧化作用

啤酒酿造废酒花（超临界CO2萃余物）中富含多酚,评价从废酒花中分离的多酚提取物（hop polyphenolextract,HPE,纯度为88.7%）对高脂血症小鼠的降脂抗氧化作用,并与同剂量的茶多酚降脂抗氧化效果进行比较。用HPE以200～800 mg/（kg·d）的剂量持续灌胃高脂小鼠5 周,高脂血症小鼠血清和肝脏中的总胆固醇和甘油三酯以及血清中的低密度脂蛋白胆固醇水平和动脉粥样硬化指数显著下降,血清中高密度脂蛋白水平显著升高。另外,小鼠血液、肝脏中的脂质过氧化产物丙二醛含量显著减少,过氧化氢酶活力显著提高,红细胞和肝脏中的超氧化物歧化酶活力、全血和肝脏中谷胱甘肽过氧化物酶活力均显著提高。研究结果表明,HPE对高脂血症小鼠具有显著的降脂和抗氧化作用。     

Volatile compounds formation in alcoholic fermentation from grapes collected at 2 maturation stages: influence of nitrogen compounds and grape variety

The aim of this work was to study the influence of nitrogen compounds on the formation of volatile compounds during the alcoholic fermentation carried out with 4 nonaromatic grape varieties collected at 2 different maturation stages. To do this, Monastrell, Merlot, Syrah, and Petit Verdot grapes were collected 1 wk before harvest and at harvest. Then, the musts were inoculated with the same Saccharomyces cerevisiae yeast strain and were fermented in the same winemaking conditions. Amino acids that showed the highest and the lowest concentration in the must were the same, regardless of the grape variety and maturation stage. Moreover, the consumption of amino acids during the fermentation increased with their concentration in the must. The formation of volatile compounds was not nitrogen composition dependent. However, the concentration of amino acids in the must from grapes collected 1 wk before harvest can be used as a parameter to estimate the concentration of esters in wines from grapes collected at harvest and therefore to have more information to know the grape oenological capacity. Application of principal components analysis (PCA) confirmed the possibility to estimate the concentration of esters in the wines with the concentration of nitrogen compounds in the must.     

国产酒花颗粒制品关键有效成分分析及在贮藏中的变化

对3个国产酒花品种青岛大花、扎一香花、马可波罗颗粒制品的的关键有效成分进行了测定并对其潜在的酿造价值进行了探讨,同时对其贮藏特性进行了研究。结果表明:3个品种的酒花颗粒制品的HSI值均高于0.35。马可波罗具有较高的酒花油和α-酸含量(分别为1.04 mL/100 g和(9.67±0.15)%),但从葎草烯/石竹烯比值、香叶烯/(石竹烯+葎草烯)比值、法呢烯的含量和α-酸/β-酸比值这3个指标来看,扎一香花具有较高的酿造价值,而马可波罗的酿造品质不佳。在惰性气体氮气条件下加速贮藏,3个品种酒花的α-酸和酒花油含量逐渐减少,但损失速率逐渐降低,β-酸、总酚、水分含量的变化无明显趋势。     

中国香型啤酒花札一的品质分析和评价

采用顸空固相微萃取方法对国产香型啤酒花品种札-的压缩花和液态CO2浸膏中的挥发性成分进行了分析,并测定了该啤酒花品种的总树脂、软树脂、硬树脂、α-酸、β-酸和啤酒花多酚等多项指标,并与国外优质香型花SAAZ的各项影响酿造性能的参数进行了比较.结果表明,札-啤酒花具有较低的α-酸含量(3.40%,w/w),其β-酸含量在3.50%(w/w),合葎草酮在α-酸中所占的比例为23.92%;挥发性成分中β-法呢烯的相对含量达到了11.52%(w/w),在浸膏中的相对含量更高(14.48%);α-香柠檬烯的含量在压缩花和浸膏中分别为0.90%和1.56%,与国际优质香型啤酒花的含量指标相符合,表明札-具有优质香型啤酒花的品质,其液态CO2浸膏基本保持了压缩花的风味特征.     

Enhanced Quantitative Extraction and HPLC Determination of Hop and Beer Bitter Acids

A pleasant and consistent bitterness is an essential flavour attribute of beer. Hop‐derived iso‐α‐acids are largely responsible for beer bitterness and accurate determination of these primary flavour compounds is very important in relation to quality control. The most widely used way to determine beer bitterness is based on spectrophotometry, measuring the absorbance of an iso‐octane extract of acidified beer. However, this approach is far from specific as it measures all of the extracted compounds, including non‐bittering principles. For that particular reason, High Performance Liquid Chromatography (HPLC) is increasingly applied for the quantitative determination of hop‐derived iso‐α‐acids and, if present, reduced iso‐α‐acids. However, to obtain accurate data on beer bitterness profiles, both quantitative sample preparation and state‐of‐the‐art HPLC are essential. In this paper, several extraction procedures based on solid phase extraction (SPE) and liquid‐liquid extraction (LLE), respectively, were evaluated and an optimised extraction methodology using H₃PO₄ for sample acidification prior to extraction is presented. The proposed extraction/HPLC methodology allows for the quantitative recovery and analysis of hop‐derived beer bitterness.