食品专业英语Lesson 5课文与讲解

Lesion 5 Alcoholic Beverages 1 课题引入课题引入 时间 5 分钟 1 结合食品业中酒精类饮料的现状和发展前景 说明学习酒精类饮料的英 文资料的必要性 讲授新内容讲授新内容 一 前言部分的翻译学习一 前言部分的翻译学习 时间 20 分钟 前言一般包括对题目研究的意义 研究的状况以及相关研究的评述和目的 等 了解前言内容 即可获知全文涉及的相关内容 Alcoholic beverages are produced from a range of raw materials but especially from cereals fruits and sugar crops They include non distilled beverages such as beers wines ciders and sake Disitlled beverages such as whisky and rum are produced from fermented cereals and molasses respectively while brandy is produced by distillation of wine Other distilled beverages such as vodka and gin are produced from neutral spirits obtained by distillation of fermented molasses grain potato or whey A variety of fortified wines are produced by addition of include sherries port and Madeira wines 二 二 正文正文 Biology of yeast fermentation 部分的翻译部分的翻译 时间 30 分钟 Biology of yeast fermentation Over 96 of fermentation ethanol is produced using strains of saccharomyces 从最初 发展和利用遗传工程技术受到相当严 格的规章控制 其涵盖了含转基因生物的利用 释放到环境中危害性 也包括现在市场上销售 的含有或由转基成分组成的食品的安全问题 很多未加工的原料都可用于生产酒精饮料 特别包括谷类 水果和糖类作物 这些酒精饮料包括非蒸馏饮料 如啤酒 葡萄酒 苹果酒和米酒 还保留蒸馏饮料 如威士忌酒和朗姆酒 这两种分别是从谷类和糖浆发酵而来 而白兰地酒是从葡萄酒蒸馏生产的 其他的蒸馏酒饮料 如伏特加酒和杜松子酒 是从发酵的糖浆 谷类 土豆或 乳清中提纯酒精而生产出的 多种加酒井的葡萄酒通过附加雪利酒 波特酒和马德拉酒而生产出的 酵母发酵的生物学 超过 96 的酒精发酵是采用的菌种都是啤酒酵母或与其相关的酵母 尤其是 奶酒酵母 葡萄糖酒 精 cerevisae or species related to it particularly saccharomyces uvarum Ethanol is produced by the Embden Meyerhof Parnas EMP parthway Pyruvate produced during glycolysis is converted to acetaldehyde and ethanol The overall effect is summarized as follows Glucose 2ADP 2Ethanol 2CO2 2ATP Theoretical yield from 1g glucose are 0 51g ethanol and 0 49g CO2 However in practice approximately 10 of the glucose is converted to biomass and yield of ethanol and CO2 may reach 90 of theoretical values The ATP formed is used to supply other cell energy requirements The yeast cell envelope contains a plasma membrane a periplasmic space and a cell wall consisting mainly of polysaccharides with a small amount of peptide material The wall component is a semi rigid but solute permeable structure which provides considerably compressional and tensile strength to yeasts Carboxyl groups of cell wall peptides confer important flocculating characteristics on brewing yeasts facilitating post fermentation solid liquid separation Flocculation is thought to result 奶酒酵母 啤酒酵母 EMP 途径是产生酒精的代谢途径 在糖酵解过程中 丙酮酸盐被转化成乙醛和酒精 全部总反应见下面公式 理论上 1 克葡萄糖可产生 0 51 克酒精和 0 49 克的二氧化碳 然而 实际生产中 近 10 的葡萄糖被转化为生物量 产生的酒精和二氧化碳的 量接近理论值的 90 形成的 ATP 用于满足其他细胞的能量需要 葡萄糖酒 精 酵母细胞的胞膜含一层质膜 周质空间和一个细胞壁 细胞壁主要由大部分多聚 糖和小部分的肽组成 该细胞壁是一种半硬质 但可溶的有透过性的结构 能够赋予酵母相当的抗压和抗张强 度 该壁中肽的羧基基团赋予细胞在发酵过程中重要的絮凝特性 这促进了发酵后期物质的固 液 分离 from salt bridge formation between calcium ions and these cell wall carboxyl groups 三 三 正文正文 Fermentation conditions 部分的翻译部分的翻译 时间 30 分钟 Fermentation conditions Fermenting S cerevisiae brewing yeast cells utilize the sugars sucrose fructose maltose and maltotriose in that distinct order Sucrose is first hydrolyzed by invertase located in the extracellular periplasmic space Sugars are transported across the cell membrane by either active or passive transport mediated by inducible or constitutively produced permeases Maltose and maltotroise are hydrolyzed intracellularly by glucosidase Saccharomyces uvarum S carlsbergensis is taxonomically distinguished from S cerevisiae in that it can also utilize melibiase Kluyveromyces fragilis and Kluyveromyces lactis which unlike S cerevisiae can ferment lactose contain a lactose permease system for lactose transport into the cell where it is hydrolyzed to glucose and galactose which enter glycolysis With the exception of Saccharomyces diastaticus which is not suitable for brewing 酵母细胞的胞膜含一层质膜 周质空间和一个细胞壁 细胞壁主要由大部分多聚 糖和小部分的肽组成 该细胞壁是一种半硬质 但可溶的有透过性的结构 能够赋予酵母相当的抗压和抗张强 度 该壁中肽的羧基基团赋予细胞在发酵过程中重要的絮凝特性 这促进了发酵后期物质的固 液 分离 认为这种絮凝是由于钙离子和细胞壁羧基集团搭建的盐桥而形成的 发酵条件 啤酒酵母利用糖进行发酵时 对蔗糖 果糖 麦芽糖和麦芽三糖有着独特的 利用次序 首先在胞外周质空间水解蔗糖 糖类再由诱导型或组成型的透性酶被主动或 被动的进行跨膜转运至胞内 麦芽糖和麦芽三糖在胞内被 葡萄糖苷酶水解 奶酒酵母 卡尔酵母 奶酒酵母 卡尔酵母 因为也可以利用蜜二糖酶 所以其在分类学上区别于啤酒酵母 脆壁克鲁维酵母乳酸克鲁维酵母 这两种克鲁维酵母不同于啤酒酵母 它们含有乳糖透性酶系统 可将乳糖转运至细胞内 从而能够将乳糖水解为葡萄糖和半乳糖而进入糖酵解途径 酵母菌属中除了糖化酵母之外 其他的不能水解淀粉和胡精 而糖化酵母不适用于酿造 Saccharomyces yeasts are incapable of hydrolyzing starches and dextrins Use of starch based materials for alcoholic fermentations requires addition of exogenous enzymes such as and amylase of malt or microbial enzymes such as amylase amyloglucosidase glucoamylase and pullulanase The major sugars of grape juice are glucose any umfermented sugar left in the resulting wine is fructose In contrast Sauterne wine yeasts ferment fructose faster than glucose 以淀粉为底物进行发酵需要额外添加酶 如麦芽中的 和 淀粉酶或者微生物中的 淀粉 酶 葡萄糖苷酶 葡萄糖化酶 和支链淀粉酶 葡萄果汁中主要的糖是葡萄糖 在葡萄酒发酵中被剩 下的糖时果糖 相反 白葡萄酒酵母发酵时果糖却比 葡萄糖快的多 Lesion 5 Alcoholic Beverages 2 课题引入课题引入 时间 5 分钟 1 复习上节课的内容 连贯起发酵控制调节部分的翻译学习 讲授新内容讲授新内容 一 正文一 正文 Fermentation conditions 部分的翻译部分的翻译 时间 70 分钟 Brewer s wort produced from barley malt contains 19 amino acids and a range of other nutrients These amino acids are assimilated at different rates during fermentation A general amino acid permease GAP can transport all basic and neutral amino acids except proline At least 11 other more specific amino acid transport systems exist in yeast Proline permease is repressed by other amino acids and ammonia While alcoholic fermentations are largely anaerobic some oxygen is needed to enable the yeast to synthesize some sterols and unsaturated fatty acid membrane components Brewer s wort normally contains sub optimal levels of sterols and unsaturated fatty acids but if the medium is supplemented with oleic or oleanoic acid the requirement for oxygen disappears Many strains of S cerevisiae can attain ethanol concentration of 12 14 Interest 从大麦芽产出的酿造麦芽汁 含有 19 种氨基酸和其他大量的营养成分 这些 氨基酸在发酵过程中以不同的速度被利用 常见的氨基酸透性酶可转运除脯氨酸之外的所有的基础型氨基酸和中间型氨基酸 至少其他 11 种特定氨基酸转运系统存在于酵母中 脯氨酸透性酶被其他氨基酸和氨抑制了活性 虽然酒精发酵一般都是在厌氧的环境中 但还是需要一些氧气来使酵母合成固醇 和不饱和脂肪酸 组成膜的成分 酿造的麦芽汁通常是包含的固醇和不饱和脂肪酸的量不充足 但在培养基中添加 油酸或油酸衍生物 则发酵过程就不需要任何氧气 多数啤酒酵母菌株都可使酒精发酵浓度达到 12 14 发酵中虽久久浓度增加 发酵速度一般降低的极快 但人们还是希望选择出可 产生 18 20 酒精的菌株 含高糖的葡萄汁仅仅可被耐高渗酵母发酵 例如鲁氏酵母菌和 baili 酵母菌 这两 株菌可高效的发酵果糖 质膜中的磷脂对于细胞耐受酒精具有重要作用 当膜不饱和脂肪酸含量增加时 细胞耐受酒精的能力也增加 在培养基中补充不饱和脂肪酸 维生素和蛋白质 可以增强细胞的耐受酒精的能力 has developed in the use of high alcohol production for distillation with a view to increasing plant productivity and decreasing distillation costs Select strains are able to produce 18 20 alcohol although fermentation rate is generally greatly reduced as ethanol concentration increase Grape juices with very high sugar and concerntrations are only fermented by osmophilic yeasts such as Saccharomyces rouxii and Saccharomyces bailli which have a high capacity to ferment fructose Plasma membrane phospholipid composition is important for ethnal tolerance Increased ethanol tolerance is observed when membrane unsaturated fatty acid content is increased Alcohol tolerance may be enhanced by supplementing the growth medium with unsaturated fatty acids vitamins and proteins Physiological factors such as the method of substrate feeding intracellular ethanol accumulation osmotic pressure and temperature all contribute to yeast ethanol tolerance Yeast glycolytic enzyme hexokinase gluceraldhydes 3 phosphate dehydrogenase and pryruvate decarboxylase have been shown to be sensitive to ethanol concentration For yeasts pH values between 3 and 6 are most favourable for growth and 考虑到降低蒸馏成本和增加产量 在高比例酿造过程和酒精蒸馏中 人们对耐酒 精能力强的酵母的利用产生越来越强的兴趣 生理学上的那些方法 如添加底物 胞内酒精积累 改变渗透压和温度 都能使 酵母耐受酒精的能力增加 酵母中分解糖的酶 己糖激酶 甘油醛 3 磷酸脱氢酶和丙酮酸脱羧酶 都对酒精 浓度敏感 pH 可影响副产物的形成 高 pH 值可增加甘油的产量 葡萄汁的 pH 一定在 3 0 3 9 范围 因为其主要含酒石酸或苹果酸而表现出的高酸度 5 15 l 除乙酸和乳酸细菌外 大多数细菌都更适宜中性 pH 值环境 从而使葡萄汁对细菌污染的敏感性大大降低 发酵中虽久久浓度增加 发酵速度一般降低的极快 但人们还是希望选择出可 产生 18 20 酒精的菌株 含高糖的葡萄汁仅仅可被耐高渗酵母发酵 例如鲁氏酵母菌和 baili 酵母菌 这两 株菌可高效的发酵果糖 质膜中的磷脂对于细胞耐受酒精具有重要作用 当膜不饱和脂肪酸含量增加时 细胞耐受酒精的能力也增加 在培养基中补充不饱和脂肪酸 维生素和蛋白质 可以增强细胞的耐受酒精的能力 fermentation activity Fermentation activity is higher at higher pH values and there is a noticeable lag in fermentation activity at pH 3 4 pH affects formation of by products High pH values increase glycerol formation The pH of grape must is usually in the range 3 0 3 9 because of its high acid content 5 15 l mainly tartaric and malic acids Since most bacteria with the exception of acetic acid and lactic acid bacteria prefer more neutral pH values the susceptibility of wine musts to infection is greatly reduced Temperature optima are distinctly different for yeast fermentation yeast respiration and cell growth Fermentation rate generally increase with