The challenge of Brettanomyces in wine

Brettanomyces spp. is an indigenous yeast that can grow during wine fermentation and impact its flavor. The characteristic flavor is often described as phenolic/medicinal, spices, cloves, earthy, barnyard, and horsy. The acceptability of Brettanoymces-induced flavors depends on the flavor intensity, personal preference, and consumer expectations. The yeast has been isolated from grapes, barrels, and winery equipment. It impacts wines from all the top producing regions in the world, with associated flavors most often found in red wines. Prevention of growth of this yeast in wine involves attention to fruit quality and winery sanitation, control of sulfite and oxygen levels, and the use uncontaminated barrels. Greater understanding of how Brettanomyces and its metabolites contribute to wine flavor is required to recognize its impact on consumer acceptability.     

ESTERASE ACTIVITY IN THE GENUS BRETTANOMYCES

During the spontaneous fermentation of Iambic and the production of the typical Belgian beer Gueuze, yeasts of the genus Brettanomyces are always found. They are especially active in the 6 to 12 months fermentation period and during refermentation in the bottle. It was found that Brettanomyces yeasts show esterase activity towards a large number of esters but especially towards esters normally found in Gueuze: ethyl acetate, ethyl lactate, iso-amyl acetate and phenethyl acetate. The esterase activity is expressed by whole cells of all Brettanomyces strains in our collection, but not by Saccharomyces or Kloeckera. The enzyme is partially purified by ammonium sulphate precipitation. It shows optimal activity at pH 7·6 for the hydrolysis of ethyl acetete and relative good stability at around 2°C. Levels of whole cell esterase activity are dependent on growth medium, aeration rate and temperature. Most interesting is the ester-synthesising activity of this esterase. Its role and influence on the ester fraction of Iambic and Gueuze seem very likely, which may then be considered as the first confirmed function of Brettanomyces during this special fermentation process.     

Role of oxygen on acetic acid production by Brettanomyces/Dekkera in winemaking

Since the large occurrence of Brettanomyces yeasts in strict anaerobiosis environments (sparkling wines) has been found without an increase in acetic acid content, we evaluated the influence of the oxygen concentration on acetic acid production. Results showed that the oxygen concentration exerted a strong influence on both growth and acetic acid production by Brettanomyces yeasts in winemaking. Full aerobiosis lead to a large production of acetic acid causing a block of metabolic activity. Semi-aerobiosis resulted in the best condition for alcoholic fermentation (Custers effect) combined with acetic acid production. In anaerobic condition Brettanomyces yeasts did not result in high acetic acid production and a pure, even if slow, alcoholic fermentation occurred. The absence of an increase in acetic acid in wines, does not exclude the active presence of Brettanomyces yeast since the characteristic ‘high acetic producer’ in Brettanomyces yeast is linked to the presence of oxygen. ©1997 SCI     

IDENTIFICATION OF LAMBIC SUPERATTENUATING MICRO-ORGANISMS BY THE USE OF SELECTIVE ANTIBIOTICS

The microbial population present in Iambic beer after one year of spontaneous fermentation consists mainly of Brettanomyces yeasts, lactic acid bacteria and acetic acid bacteria. The density of the wort by that time has decreased to around 3.5° Plato. At that time a period of superattentuation is initiated, resulting in a Iambic with sometimes less than 1° Plato. Such old Iambics are used in the production of gueuze. In order to find out which organisms are really necessary for this process. Iambic attenuated to around 3.5° Plato was pasteurized and re-inoculated with a mixed microbial population obtained from fermenting Iambic. By the addition of the antibiotics actidione, pimaricin, gentamycin, oxytetracycline and nisin it was found that Brettanomyces was the main organism responsible for superattenuation, although this was less pronounced when Pediococcus was absent. Acetic acid bacteria were not involved. Bacteria alone were not really superattenuating. The process with Iambic wort which had reached the 3.5° Plato value by a natural spontaneous fermentation was slower than with a Iambic wort pre-fermented to 3.5° Plato with S. cerevisiae. It was found that Brettanomyces but not Saccharomyces survives well under the conditions normally found for a 1 year old Iambic.     

搅拌型酸奶后酸化控制的初步研究

文中针对搅拌型酸奶成熟后在贮存、运输、销售、食用前出现的后酸化现象(postacidification)文中进行了初步研究。在无水乙醇抑制后酸化的实验中,4%的无水乙醇能明显抑制乳酸菌的进一步产酸,且不影响其优良的感官指标。进一步研究发现,每40mL酸奶制品分别添加1.4mL酒精度为38%的汾酒、1.0mL酒精度为62%的高度酒均可明显抑制后酸化现象。文中还尝试了酵母菌抑制后酸化的效果,结果发现,1株从牧区家庭自制酸奶中分离的酵母菌以2.0×107个/mL的浓度,每40mL酸奶制品添加0.1mL不仅可抑制后酸化现象,而且轻微的乙醇发酵改善了酸奶的口味,提高了酸奶的感官品质。经细胞形态、菌落特征、生理生化及产孢子类型可初步判断该酵母菌为异酒香酵母。     

黑加仑果渣提取物抗氧化活性研究

以黑加仑果汁加工后的果渣为原料,通过微波-超声辅助提取法提取果渣中多糖及水、醇萃取物;采用体外抗氧化体系研究果渣提取物超氧自由基、羟基自由基、DPPH自由基的清除能力,采用红外对多糖进行表征。结果表明:多糖为α-吡喃糖;多糖、醇提取物浓度在0.8 mg/mL时DPPH自由基、羟基自由基清除率达到90%以上,水提取物达到80%以上;其多糖超氧自由基清除率达到60%以上;水、醇提取物超氧自由基在50%以上。所以,提取物具有显著抗氧化活性,具有好的开发前景。     

对葡萄酒酒香酵母属不良风味抑制的研究进展

酒香酵母属是葡萄酒中固有的一种微生物,影响葡萄酒的品质.它在葡萄酒酿制的整个过程中代谢产生一种以4-乙基苯酚和4-乙基愈创木酚为典型的风味特征的一类不良风味,这些不良风味的存在降低了葡萄酒的品质,从而对葡萄酒工业造成严重的经济损失.本文对酒香酵母属的生理特征和葡萄酒易受其感染的原因进行综述以及对不良风味的抑制方法进行分类综述,以期国内葡萄酒工业对酒香酵母属不良风味的抑制有所借鉴.     

苹果渣及板栗渣黄芪酒加工工艺研究

以苹果渣和板栗渣为主要原料,添加黄芪提取液,研究配制酒的最佳前处理条件.苹果渣和板栗渣分别经前处理、酶解后,按比例混合发酵后经常压蒸馏制酒,考察黄芪提取液的最佳制备工艺,将其添加到蒸馏酒中配制成苹果渣板栗渣黄芪配制酒.结果表明,最佳苹果渣前处理条件为蒸煮时间30 min、果胶酶添加量0.3％、酶解时间3 h、酶解温度5...     

红枣果汁果渣与果酒果渣中色素抗氧化活性的比较

为比较红枣果汁果渣与果酒果渣中色素抗氧化活性的差异,以红枣果汁及果酒果渣为原料,碱法提取红枣色素,运用比色法测定红枣果汁果渣、果酒果渣色素中抗氧化活性成分含量,测定DPPH·、ABTS⁺·、·OH、O₂^-·清除能力和还原力,比较红枣果汁果渣与果酒果渣色素的抗氧化活性,采用SPSS软件分析抗氧化活性成分含量与抗氧化活性之间的相关性。结果表明:红枣果汁果渣与果酒果渣色素抗氧化活性成分含量间存在显著差异(P<0.05),且随着发酵时间延长,色素抗氧化活性成分含量逐渐降低;红枣果汁果渣与果酒果渣色素清除DPPH·、ABTS⁺·、·OH、O₂^-·能力和还原力差异显著(P<0.05),随着发酵时间延长,色素抗氧化活性逐渐降低;相关性研究显示,果汁果渣色素抗氧化活性成分含量与抗氧化活性相关性较强,果酒果渣色素总黄酮含量与抗氧化活性相关性相对较弱,表明红枣果汁果渣色素抗氧化活性显著高于果酒果渣(P<0.05)。     

亚硫酸铵和卤水制无水亚硫酸钠工艺研究

亚硫酸铵和卤水在60℃下,n(NaCl)/n[(NH4)2SO3]=2.0～2.1的条件下反应得Na2SO3晶体,经分离、洗涤、干燥后得无水亚硫酸钠产品.分离Na2SO3后的母液Ⅰ冷至20℃,析出NH4Cl晶体,将分离NH4Cl后的母液Ⅱ浓缩结晶得Na2SO3晶体,分出Na2SO3后的残液与母液Ⅱ混合,送去浓缩结晶.将分出的NH4Cl干燥得氯化铵副产品.该工艺的优点是原料成本低,副产氯化铵,经济效益好,无污染.     

亚硫酸铵和卤水制无水亚硫酸钠工艺研究

亚硫酸铵和卤水在60℃下，n（NaCl）／n[（NH4）2SO3]：2．0～2．1的条件下反应得Na2SO3晶体，经分离、洗涤、干燥后得无水亚硫酸钠产品。分离Na2SO3后的母液Ⅰ冷至20℃，析出NH4Cl晶体，将分离NH4Cl后的母液Ⅱ浓缩结晶得Na2SO3晶体，分出Na2SO3后的残液与母液Ⅱ混合，送去浓缩结晶。将分出的NH4Cl干燥得氯化铵副产品。该工艺的优点是原料成本低，副产氯化铵，经济效益好，无污染。     

红枣果汁果渣与果酒果渣膳食纤维功能特性的比较研究

为了探究红枣果汁果渣与果酒果渣膳食纤维功能特性的差异,以红枣果汁果渣和果酒果渣为原料制备膳食纤维,通过测定膳食纤维的持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力,评价红枣果汁果渣与果酒果渣膳食纤维的功能特性。结果表明:红枣果酒果渣膳食纤维的持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力均显著高于果汁果渣膳食纤维(P<0.05),且随发酵天数延长,红枣果渣膳食纤维的功能特性均逐渐增加。发酵8 d时,果酒果渣膳食纤维持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力较果汁果渣膳食纤维分别提高了1.10、1.11、1.75、1.39、2.03、1.49、1.10和1.83倍,表明发酵有助于提高红枣果渣膳食纤维的功能特性。     

对碱性和中性亚硫酸盐法制浆废液综合利用的探讨

从综合利用的角度出发,对比了AS-AQ法落叶松蒸煮废液(AS-L)、NS-AQ法杨木蒸煮废液(NS-L)及二者按1:4体积比混合而成的废液(M-L),与钙盐基酸性亚硫酸盐法木浆蒸煮废液(Ca-L)和亚硫酸氢镁法苇浆蒸煮废液(Mg-L)的组成成分、表面活性、废液粘度等基本性质,也对作为粘结剂、木素铁铬盐、水泥减水剂等应用性质进行了比较.与Ca-L和Mg-L相比,AS-L、NS-L和M-L的无机物含量高20%～30%,木素磺酸盐含量较Ca-L和Mg-L低2～4个百分点,废液粘度远低于Ca-L和Mg-L,但表面活性高于Ca-L和Mg-L.将固含量为50%的废液直接用作锌矿粉的粘结剂、合成油田钻井用木素铁铬盐及水泥减水剂,AS-L、NS-L和M-L的使用效果都相当于或优于Ca-L和Mg-L.     

红薯、苹果醋饮品的开发

介绍了以红薯淀粉提取过程中的废液和苹果渣为主要原料生产红薯、苹果醋饮品的生产工艺及操作要点.     

油橄榄果渣油的提取工艺及其脂肪酸组成研究

以油橄榄加工废渣为原料,研究了提取条件对果渣油提油率的影响.结果表明:果渣水分含量在10％以下时适宜果渣油的提取,最佳的萃取溶剂为正己烷;响应面法优化的正己烷萃取条件为提取转速200 r/min、提取时间3h、提取温度55℃、料液比1:9;在此优化条件下的预测提油率为9.46％,验证值为9.16％,模型预测精度达96.8％.气相色谱-质谱(GC -MS)分析结果表明,正己烷萃取的果渣油主要脂肪酸为油酸(68.73％)、棕榈酸(15.28％)、8,10-二甲氧基-十八烷酸(6.65％)、亚油酸(2.80％)、硬脂酸(2.78％)和棕榈油酸(0.97％),其主要脂肪酸组成与橄榄油类似.