酵母菌发酵实验报告英文
关于发酵食品的英语作文
The Fascinating World of Fermented FoodsFermentation is one of the oldest and most widespread food preservation techniques known to humanity.This ancient process,which involves the transformation of food by microorganisms,has given rise to a diverse array of flavors,textures,and nutritional benefits.From tangy sauerkraut to creamy yogurt,fermented foods are enjoyed across cultures and have become a staple in many diets.This essay delves into the fascinating world of fermented foods,exploring their history,the science behind fermentation,and the various health benefits they offer.A Brief History of FermentationFermentation has been practiced for thousands of years,with evidence of fermented foods dating back to ancient civilizations.The earliest records of fermentation can be traced to the Neolithic period,around 7000-6600BCE,when people began to ferment grains and fruits to produce alcoholic beverages.Ancient Egyptians,Greeks,and Romans also embraced fermentation,using it to make bread,wine,and cheese.Throughout history,fermentation has played a crucial role in food preservation,allowing communities to store food for extended periods. This was particularly important before the advent of refrigeration. Fermented foods also became integral to cultural and religious practices, with many traditional recipes being passed down through generations. The Science of FermentationFermentation is a metabolic process in which microorganisms such as bacteria,yeast,and molds convert sugars and other carbohydrates into alcohol,acids,and gases.This process not only preserves food but also enhances its flavor,texture,and nutritional value.There are several types of fermentation,each involving different microorganisms and resulting in distinct products:Lactic Acid Fermentation:This type of fermentation is carried out by lactic acid bacteria,which convert sugars into lactic acid.It is responsible for the tangy taste and extended shelf life of foods like yogurt, sauerkraut,kimchi,and pickles.Alcoholic Fermentation:Yeasts,particularly Saccharomyces cerevisiae, convert sugars into alcohol and carbon dioxide.This process is used to produce alcoholic beverages such as beer,wine,and sake,as well as leavened bread.Acetic Acid Fermentation:Acetic acid bacteria convert alcohol into acetic acid,resulting in the production of vinegar.This type of fermentation is used to make various types of vinegar,including apple cider vinegar and balsamic vinegar.Mold Fermentation:Certain molds,such as Aspergillus oryzae and Penicillium roqueforti,are used in the fermentation of foods like soy sauce,miso,and blue cheese.These molds contribute to the unique flavors and textures of these products.Health Benefits of Fermented FoodsFermented foods are not only delicious but also offer a range of health benefits.The fermentation process enhances the nutritional profile of foods and introduces beneficial microorganisms,known as probiotics, which support gut health.Some of the key health benefits of fermented foods include:Improved Digestion:Probiotics in fermented foods help maintain a healthy balance of gut bacteria,which is essential for proper digestion. They can alleviate symptoms of digestive disorders such as irritable bowel syndrome(IBS)and reduce bloating and gas.Enhanced Nutrient Absorption:Fermentation breaks down complex compounds in food,making nutrients more bioavailable.For example, the fermentation of dairy products increases the availability of calcium and B vitamins.Boosted Immune System:A healthy gut microbiome is closely linked to a strong immune system.Probiotics in fermented foods can enhance the body's ability to fight off infections and reduce inflammation. Reduced Risk of Chronic Diseases:Regular consumption of fermented foods has been associated with a lower risk of chronic diseases such as heart disease,diabetes,and certain cancers.The antioxidants and anti-inflammatory compounds produced during fermentation contribute to these protective effects.Mental Health Benefits:Emerging research suggests that gut health is connected to mental health through the gut-brain axis.Probiotics in fermented foods may help alleviate symptoms of anxiety and depression by promoting a healthy gut microbiome.Popular Fermented Foods Around the WorldFermented foods are enjoyed in various forms across different cultures, each with its unique flavors and traditions.Here are some popular fermented foods from around the world:Yogurt:A staple in many diets,yogurt is made by fermenting milk with lactic acid bacteria.It is known for its creamy texture and tangy flavor.Sauerkraut:This German delicacy is made by fermenting shredded cabbage with salt.The result is a tangy,crunchy,and probiotic-rich food.Kimchi:A traditional Korean dish,kimchi is made by fermenting vegetables,usually cabbage and radishes,with chili peppers,garlic, ginger,and fish sauce.It is known for its spicy and pungent flavor.Kombucha:A fermented tea beverage,kombucha is made by fermenting sweetened tea with a symbiotic culture of bacteria and yeast(SCOBY).It is fizzy,tangy,and slightly sweet.Tempeh:Originating from Indonesia,tempeh is made by fermenting soybeans with a mold called Rhizopus.It has a firm texture and nutty flavor,making it a popular plant-based protein source.Miso:A staple in Japanese cuisine,miso is a fermented soybean paste used to flavor soups,sauces,and marinades.It has a rich,umami flavor.Cheese:Various types of cheese,such as blue cheese,cheddar,and brie, are made through fermentation.The process involves the action of bacteria and molds,contributing to the distinct flavors and textures of each cheese.ConclusionThe fascinating world of fermented foods offers a rich tapestry of flavors, textures,and health benefits.From ancient preservation techniques to modern culinary delights,fermentation has played a vital role in shaping our diets and cultures.By embracing fermented foods,we can enjoy their unique tastes and reap the numerous health benefits they provide. Whether it's a spoonful of tangy yogurt,a bite of spicy kimchi,or a sip of fizzy kombucha,fermented foods continue to captivate and nourish people around the world.。
酵母菌实验报告
酵母菌实验报告酵母菌是一种单细胞真菌，广泛存在于自然界中，可以进行无性繁殖和有性繁殖。
酵母菌被广泛应用于食品工业、生物科技、医药领域和环境保护等领域。
为了更好地了解酵母菌的生长和繁殖规律，我们开展了一项实验。
实验设计本次实验主要是研究酵母菌的生长曲线和pH值对其生长的影响。
实验共分为三组。
第一组：不加pH调节液，观察酵母菌的生长情况。
第二组：加入pH调节液，将pH值保持在6左右，观察酵母菌的生长情况。
第三组：加入pH调节液，将pH值保持在4左右，观察酵母菌的生长情况。
实验过程我们选取了常见的酵母菌——啤酒酵母（Saccharomyces cerevisiae）进行实验。
首先，我们制备了发酵液，将其注入培养皿中。
然后，我们将酵母菌取出，在无菌条件下添加到发酵液中。
在第一组中，不进行pH值调节；在第二组和第三组中，加入适量的pH调节液，以调整pH值。
接下来，我们将培养皿放入恒温培养箱中，设置温度为30℃，并对三组实验进行观察。
实验结果我们观察发现，在没有进行pH调节液的情况下，酵母菌在第一组中的生长情况非常不稳定。
在第六天，酵母菌生长达到了峰值，但在第七天开始急剧下降，到第十天时基本上停止生长。
相比之下，加入pH调节液的第二组和第三组，酵母菌的生长情况更加稳定。
在第二组中，pH值维持在6左右，酵母菌的生长情况一直保持在适宜的水平。
在第三组中，pH值维持在4左右，酵母菌的生长速度略有下降，但仍然保持了相对稳定的生长状态。
结论通过此次实验，我们可以得出以下结论：1. pH值对酵母菌的生长有很大的影响。
在酵母菌的生长过程中，pH值的变化会引起酵母菌的代谢和繁殖速度变化，影响其生长状态。
2. 在没有进行pH调节液的情况下，酵母菌的生长非常不稳定，生长速度快慢不一，难以控制。
3. 通过适当调节pH值，可以使酵母菌的生长更加稳定，有利于生产过程的控制和优化。
本次酵母菌实验结果较为成功，我们除了发现了pH值对酵母菌的生长影响外，还得到了很多有利的数据和图表。
酵母菌培养研究报告怎么写
酵母菌培养研究报告怎么写1. 引言酵母（Saccharomyces cerevisiae）是一种常见的单细胞真菌，可广泛应用于食品、药物和生物燃料等领域。
酵母菌培养研究旨在探究酵母生长和代谢特性，以及相关因素对酵母生长的影响。
本报告将介绍酵母菌培养研究的基本步骤、实验设计和数据分析方法。
2. 实验设计2.1 实验目的本实验旨在研究不同培养基组分对酵母菌生长速率的影响。
2.2 实验材料•酵母菌培养基•不同组分的培养基配方•培养皿•离心机•显微镜2.3 实验步骤1.准备不同组分的培养基。
2.将酵母菌菌种接种到不同培养基中。
3.以相同温度（例如25°C）下培养不同组的酵母菌培养基。
4.在培养一定时间后，观察酵母菌的生长情况。
5.通过显微镜观察和计数酵母菌细胞数量。
3. 数据分析3.1 数据采集在实验过程中，观察并记录酵母菌在不同组分培养基中的生长情况，包括菌落大小、颜色和细胞数量。
3.2 数据处理对采集的数据进行统计和分析，计算平均菌落直径、平均菌落颜色的变化以及细胞数量的平均值。
3.3 数据展示使用统计图表展示数据结果，例如绘制柱状图展示不同培养基对酵母菌生长速率的影响。
4. 结果与讨论4.1 实验结果根据数据分析，不同组分的培养基对酵母菌生长速率有显著影响。
结果表明XXX培养基对酵母菌生长的影响最显著，其菌落直径达到最大值，颜色变化明显。
而在XXX培养基中，酵母菌生长速率较低。
4.2 结果讨论从实验结果可以推测，酵母菌对培养基中特定组分的反应较为敏感。
XXX组分可能含有有利于酵母菌细胞生长和繁殖的营养成分，从而促进了菌落的增长和细胞数量的增加。
该实验结果对酵母菌培养研究具有重要意义，为进一步探索酵母菌代谢特性和应用提供了理论基础和实验依据。
5. 结论本研究结果表明，不同组分的培养基对酵母菌生长速率有显著影响。
未来的研究可以进一步探究不同组分对酵母菌代谢产物的影响，以及酵母菌与其它微生物的相互作用。
酵母菌培养实验报告
酵母菌培养实验报告
酵母菌是一类单细胞真菌，广泛存在于自然界中，其具备着高效
的发酵能力，因此在生产中有着极为重要的地位。
为了更好地研究和
利用酵母菌，我们进行了酵母菌的培养实验，下面是本次实验的详细
过程和结果。
材料与方法：
材料：枸杞果酱、葡萄糖、酵母菌（Saccharomyces cerevisiae）方法：
1、准备培养基：按照配方将枸杞果酱、葡萄糖和蒸馏水混合均匀，加热至沸腾，去掉表面的泡沫；
2、接种：在无菌条件下，取一小块酵母菌添加至培养基中；
3、培养：常温下放置培养瓶中，观察酵母菌生长情况并记录；
4、观察和记录：每隔一段时间观察培养瓶中的酵母菌生长情况，如形态、数量、颜色等，并记录；
5、计算生长曲线：根据观察结果，绘制出酵母菌生长曲线。
结果分析：
酵母菌培养过程中，最初的24小时内酵母菌数量迅速增长，然后
逐渐趋于平稳。
观察到酵母菌形态呈圆形或椭圆状，颜色为乳白色或
淡黄色。
而后续的观察结果表明，酵母菌的生长速度会随着时间的推
移而下降。
此时，我们计算了酵母菌生长曲线，发现其呈现出“S”形状，这表明酵母菌的生长具有较好的适应性。
结论：
通过本次实验，我们了解到了酵母菌在不同条件下的生长情况，以及如何绘制酵母菌生长曲线。
同时，我们也将在未来的实验中，更加深入地研究酵母菌的特性与应用，来促进食品、饮料等领域的技术进步。
酵母发酵外文
Electronic Journal of Biotechnology ISSN: 0717-3458DOI: 10.2225/vol14-issue2-fulltext-5 RESEARCH ARTICLE Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast densityAdemola O. Olaniran1 · Yushir R. Maharaj1 · Balakrishna Pillay11 Discipline of Microbiology, School of Biochemistry, Genetics and Microbiology, Faculty of Science and Agriculture, University of KwaZulu-Natal, Republic of South AfricaCorresponding author: olanirana@ukzn.ac.zaReceived May 3, 2010 / Accepted January 3, 2011Published online: March 15, 2011© 2011 by Pontificia Universidad Católica de Valparaíso, ChileAbstract Production of good quality beer is dependent largely on the fermentation temperature and yeast strains employed during the brewing process, among others. In this study, effects of fermentation temperatures and yeast strain type on beer quality and spent yeast density produced after wort fermentation by two commercial yeast strains were investigated. Beer samples were assessed for colour, clarity and foam head stability using standard methods, whilst the compositions and concentration of Beer Volatile Compounds (BVCs) produced were assessed using GC-MS. The spent yeast density, measured as dry cell weight, ranged between 1.84 - 3.157 mg/ml for both yeast strains with the highest yield obtained at room temperature fermentation. A peak viable population of 2.56 x 107 cfu/ml was obtained for strain A, also during fermentation at room temperature. The foam head of the beers produced at 22.5ºC was most stable, with foam head ratings of 2.66 and 2.50 for yeast strain A and B, respectively. However, there was no significant (p= 0.242) difference in colour intensity between the beers produced at the different fermentation temperatures. Eight different BVCs were detected in all beer samples and were found to affect the organoleptic properties of the beer produced. Further optimizations are required to determine the effects of other parameters on beer quality. Keywords: beer volatile compounds, fermentation temperature, organoleptic quality, spent yeast densityINTRODUCTIONBeer brewing is an established ancient art from as far back as 6000 B.C., during the building of the ancient cities of Mesopotamia (Cortacero-Ramirez et al. 2003) and has been practised for thousands of years. The practice of producing beer in small micro-breweries has been replaced by magnificent industrial production plants that push out volumes of beer that early brew-masters could only dream about (Rojas and Peterson, 2008). To facilitate effective fermentation process, the yeast is often pitched at a specific population size and allowed to grow via an aerobic step in the fermentation process (Tanguler and Erten, 2008). Fermentation temperature is known to influence beer aroma composition (Bekatorou et al. 2002). Low temperature brewing; in particular, has been reported to result in the production of beer with improved taste and aroma as well as high ethanol and beer productivities (Bardi et al. 1996a; Bardi et al. 1997). Immobilized cell technology processes have been shown to shorten the production time of beer from 12-15 days to 1-3 days, however, the major difficulty is to achieve the correct balance of sensory compounds to create an acceptable flavour profile within the time frame (Willaert and Nedovic, 2006). Beer produced by fermentation of wort by cells immobilized on glutten pellets have been reported to have reduced higher alcohols and higher ethyl acetate (Bardi et al. 1996b).After the fermentation process, there is often a much greater amount of spent yeast present in the fermenter than that present at pitching (Shotipruk et al. 2005). The spent yeast generated during the fermentative process is often used as an inoculum for subsequent fermentations (Blieck et al. 2007). InOlaniran et al.addition, yeast cell wall fractions contain a large percentage of β-glucans, which is highly advantageous in improving the physical and functional properties of foods, as a thickening and water-holding agent (Thammakiti et al. 2004) and for the gelatinization and retrogradation of starch (Satrapai and Suphantharika, 2007). β-glucans isolated from the cell wall fractions of spent brewer’s yeast are good emulsifying stabilizer and are finding application as a form of fat replacement in the production of low-fat mayonnaise (Burkus and Temelli, 2000). The partial replacement of vegetable oil in mayonnaise using β-glucans derived from spent yeast extract has two distinct advantages; firstly, it decreases the calorie content of the emulsification and secondly, it results in the utilisation of industrial by-products (Worrasinchai et al. 2006). In addition, β-glucans have been reported to have been used as a form of immunomodulator in livestock (Eicher et al. 2006).The fermentation step in beer production is facilitated through the metabolic activities of yeast, resulting in the conversion of fermentable sugars to carbondioxide (CO2) and ethanol (Piškur et al. 2006). Whilst these metabolic activities produce the required ethanol from the fermentation, they also result in the production of large amounts of metabolic by-products, beer volatile compounds (BVCs), such as esters, ketones and higher alcohols which if present in high concentrations can influence the final aroma and flavour profile of the beer (Hansen, 1999; Šmogrovičoví and Dömény, 1999; Brown and Hammond, 2003; Vanbeneden et al. 2008). These compounds are derived from precursors of yeast metabolic pathways and some of them are essential for growth of the yeast (Brown and Hammond, 2003). Whilst the presence of these compounds may be considered as detrimental to many (especially those in industry), there are a select few that regard these compounds as important flavour enhancers, especially those with an acquired taste for speciality beers. It is therefore important to determine the effects of these BVCs on beer quality as well as the mechanisms involved in their generation in order to develop methods to facilitate their control.Over the past three decades, research in brewing has focussed on the application of immobilized cells, mainly to facilitate continuous processing, shorten maturation time and consequently reduce production costs (Kopsahelis et al. 2007). However, there appears to be limited studies on the effects of fermentation parameters on the production of BVCs and the consequences on the organoleptic quality of the final product as well as on the spent yeast density produced. This study is therefore aimed at investigating the effects of fermentation temperatures and yeast strain type on the production of spent yeast and BVCs as well as on the overall quality of beer produced. This would have significant repercussions on the South African economy, especially because the beer industry is a considerable player in the country’s economy, and the continuous increase in demand by the consumer.MATERIALS AND METHODSWort preparation and fermentationThe wort used for the fermentation was made using canned-hopped malt extract purchased from National Food Products (Johannesburg, South Africa) and was prepared according to the manufacturer’s instructions. Fermentations were set-up to determine the effects of different fermentation temperatures and commercial yeast strains on beer quality using mini-fermenters (3.5 L) designed to facilitate the fermentation process on a small scale. Two litres of wort was dispensed into each sterile fermenter vessels after being allowed to cool and sterile standard rubber tubing (5 mm inner diameter) was attached to the outlets for sampling. The free end of the tubing was placed into a 2 l flask containing sterile distilled water to form the air-lock. Two commercial yeast strains, National Food Product yeast and Anchor yeast (designated as “strain A” and “strain B”, respectively) were used to pitch the fermentation. The yeast strains were grown in malt extract broth for 24 hrs at 30ºC with shaking at 120 rpm and then pitched at an optical density of 0.4 at an absorbance of 600 nm, which corresponds to a cell density of 5 x 106Colony forming units per millilitre (cfu/ml) according to the McFarland standard. The fermenters containing each type of yeast were then incubated at one of three fermentation temperatures viz., room temperature (RT) (± 18ºC), 22.5ºC and 30ºC for a period of one week. These temperatures were chosen to check the effects of the varying temperature ranges on the composition and concentrations of volatile compounds in the final beer. Gas evolution was monitored from the air-lock mechanism to ensure that fermentations were not stuck.Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density Bottling and bottle conditioningAfter a period of one week, the beer from each fermenter was aseptically transferred into sterile 500 ml sample bottles. To each bottle, a teaspoon of sugar was added prior to the addition of beer for bottle conditioning and the bottles were sealed and allowed to condition for a period of one week. After bottle conditioning, all bottles were stored at 4ºC to facilitate yeast settlement and the maturation process.Measurement of spent yeast density and viabilitySpent yeast density was measured by the method of Soley et al. (2005). Ten millilitre samples were removed from each fermenter after fermentation and centrifuged (6000 rpm for 10 min at 4ºC). The pellet was washed and resuspended in a normal saline solution (0.9% w/v NaCl), filtered through a previously dried and pre-weighed Whatman grade GF/A (Ø 47 mm) glass microfiber filter, and dried to a constant weight at 105ºC. Thereafter, weight of the filter was subtracted from the weight of the filter containing the dried cellular material to acquire the mass of spent yeast produced. Viable yeast cell population was determined by the method of Nagodawithana et al. (1974). Yeast cells present in fermentation reactor were first thoroughly dispersed to ensure equal distribution of cells. Thereafter, a 1-ml sample was serially diluted before spread plating 0.1 ml of appropriate dilutions onto malt extract agar. The plates were incubated at 30ºC for 48 hrs, and the number of colonies on plates for the dilution containing 30 to 300 colonies were counted and expressed as colony forming units per millilitre (cfu/ml).Analysis of BVCsAnalysis of BVCs present in the beer samples was measured using dynamic headspace extraction methods and analyzed by gas chromatography and mass spectrometry (GC-MS). The volatiles from 100 ml of each sample was assessed by enclosing the sample bottle in a polyacetate bag and pumping air from the bag through a small cartridge filled with 1 mg of tenax® and 1 mg of carbotrap® activated charcoal at a flow rate of 50 ml/min for 30 min. A control was taken from an empty polyacetate bag sampled for the same duration. GC-MS analysis of the samples was carried out using a Varian CP-3800 GC (Varian, Palo Alto, California) with a 30 m x 0.25 mm internal diameter (film thickness 0.25 µm) Alltech EC-WAX column coupled to a Varian 1200 quadruple mass spectrometer in electron-impact ionization mode. Cartridges were placed in a Varian 1079 injector equipped with a “Chromatoprobe” thermal desorbtion device. Helium was used as a carrier gas at a flow rate of 1 ml min-1. The injector was held at 40ºC for 2 min with a 20:1 split and then increased to 200ºC at 200ºC min-1 in splitless mode for thermal desorbtion. After a 3 min hold at 40ºC, the GC oven was ramped up to 240ºC at 10ºC min-1and held there for 12 min. Compounds were identified using the Varian workstation software with the NIST05 mass spectral library and verified, where possible, using retention times of authentic standards and published Kovats indices. Compounds present at similar abundance in the control were considered to be contaminants and excluded from analysis. To ensure accuracy with quantification of emission rates, standards were injected into cartridges and thermally desorbed under identical conditions to the samples.Measurement of foam head stabilityThe foam head stability was assessed according to the modified mini foam shake test developed by Van Nierop et al. (2004). A 20 ml sample of each beer (in triplicate) was dispensed into 50 ml glass measuring cylinders and all of the cylinders were sealed with parafilm. Each set of cylinders were shaken at the same time, vigorously up and down 10 times, after which the cylinders were set down on the counter, the parafilm pierced, and a timer set for 15 min. The foam was evaluated visually and the cylinders were arranged from best to worst. Ratings of 1 through 3 were given, where 3 was the greatest stability and 1 the worst.Analysis of beer clarity and colourThe clarity of the beer was determined using a Hach P2100 Turbidimeter, while beer colour was measured spectrophotometrically at a wavelength of 430 nm as described elsewhere (Seaton and Cantrell, 1993). In both cases, distilled water served as a blank and a commercial beer was included in the analysis as positive control.Olaniran et al.Organoleptic quality assessmentThe taste profile of beer produced was assessed by a survey conducted with 10 independent samplers, with no previous beer quality assessment skills. The survey consisted of questionnaires asking the samplers to rate beer from 1 to 10 (1 being very bad and 10 being excellent), for the presence of 10 different characteristics such as; banana aromas, sour apple taste, sweet “butterscotch” aroma, etc. Samplers were asked to give a rating of 0 if they felt a certain trait was absent. These values were assigned categories such that a rating from 0 - 3 was regarded as “low”, 4 - 6 as “medium” and 7 - 10 “high”. The data obtained was then used to determine the percentage of samplers which felt that the presence of the compounds was “low”, ”medium” or “high”. A commercial beer was also sampled to serve as the control.RESULTS AND DISCUSSIONSpent yeast density and viable yeast population recovery after fermentationEffect of the different fermentation temperatures on the spent yeast density and viable yeast population was investigated. Spent yeast density decreases with increasing fermentation temperature (Figure 1a). Fermentation at room temperature produced the most spent yeast density with a yield of 2.47 mg/ml and 3.15 mg/ml obtained for strain A and strain B, respectively. Spent density of strain A produced at a fermentation temperature of 22.5ºC was almost equal to that produced at room temperature, with only 1.215% reduction in the spent yeast density whilst only 8.25% less of strain B spent density was produced at 22.5ºC compared to that produced at the room temperature. It is possible that the available fermentable sugars present at these temperatures were converted into biomass at a similar rate as these temperatures are relatively close to 18ºC, which is the upper temperature limit that is commonly used for lager beer fermentations (Brown and Hammond, 2003). The 30ºC fermentation resulted in the lowest spent yeast density production of both strains with a 25.50% and 32.06% reduction in spent density produced compared to the room temperature fermentations for strain A and strain B, respectively. The reduction of spent yeast density and viable yeast population after fermentation at 30ºC could be attributed to increased metabolic rate at this higher temperature which could have led to faster utilization of sugars, and resulting in cell starvation, cell death and autolysis (Blieck et al. 2007).Similarly, an increase in fermentation temperature led to a steady decrease in the viability of yeast cells (Figure 1b). A peak density of 2.56 x 107 cfu/ml was obtained for strain A at room temperature, which is about 2-fold higher than those obtained for strain B at 22.5ºC fermentation. The least viable population of both strains was observed at 30ºC fermentation, with about 11-fold and 3-fold reduction in population of yeast strain A and B, respectively, obtained compared to the peak population. In this study, fermentations was conducted for a period of 7 days disregarding the specific gravity of the wort, which is generally used to determine the remaining fermentable sugar concentrations in the wort solution in order to know when to terminate the fermentation process. Thus, it is possible that all fermentable sugars have been utilised before termination of the fermentation. Previous studies have shown a decrease in cell density as a result of decrease in fermentable sugars present in the wort. The decrease in cell viability with time has also been attributed to nutrient depletion and early entry of the organisms into the death phase (Blieck et al. 2007).Beer colour, clarity and foam head stabilityThere was no significant (p = 0.242) difference in colour developed between the experimental beers produced by the yeast strains under the different fermentation temperatures; however, the colour intensity of all experimental beers was significantly (p < 0.05) lower than that of the control beer. The control beer had the deepest colour intensity with an absorbance of 0.198, while the maximum absorbance for beer produced with strain A and B at room-temperature was 0.149 and 0.143, respectively, with a maximum absorbance of 0.144 obtained for beer produced with the two strains at 22.5ºC (Figure 2a). Also, the absorbance of beer produced with strain A and B at 30ºC was 0.143 and 0.135, respectively (Figure 2a). Colour development in beer has been mostly attributed to the malt extract used in the respective beers instead of the fermentation parameters (Kopsahelis et al. 2007). Generally, the malt extract used has been reported to have the greatest effect on beer colour as the degree of colour intensity of the malt extract depends on the degree of kilning or roasting of the maltedEffects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast densitybarley (Seaton and Cantrell, 1993; Kopsahelis et al. 2007). Thus, it is possible that the control beer may have been produced from a malt extract which was differentially roasted compared to the malt extract used in this study.There was no direct correlation between fermentation temperature and the clarity of beer produced with the two yeast strains. However, beers produced with strain B were generally clearer compared to those produced using strain A, with 56.13%, 21.46% and 57.58% reduction in turbidity at room temperature, 22.5ºC and 30ºC fermentation temperatures, respectively (Figure 2b). All the experimental beers produced were relatively turbid compared to the control. The extremely good clarity found in the control beer may be attributed to additional processing steps, such as centrifugation and microfiltration, that are used in the production of commercial beers (such as the control) to increase clarity (Seaton and Cantrell, 1993; Kuiper et al. 2002; Shotipruk et al. 2005). The beers produced inthis experiment were bottle conditioned and were not subjected to further processing as the control beer. Also, it has been generally observed that bottle conditioned beers are more turbid than their commercial counterparts due to the presence of the residual yeast used for conditioning (Kuiper et al. 2002). It was also noted that yeast strain A produced beer with higher turbidity than strain B and this could be that yeast strain A produced and released higher concentrations of haze active proteins since the presence of these proteins has been shown to increase turbidity in beer (Seaton and Cantrell, 1993).The control beer used had the best foam head stability compared to the experimental beers. The foam head of the experimental beers produced at 22.5ºC was most stable, retaining as high as 88.67% foam head stability compared to the control beer, while those prepared at room temperature had the least foam head stability rating (Figure 3). This could be due to variations in climatic temperature and lightFig. 1 Spent yeast density (a) and Total yeast viable population (b) produced by different yeast strains at the different fermentation temperatures. Values are average from six values ± standard deviationOlaniran et al.intensity at room temperature which could have stressed the yeast cells and hence led to alterations in the yeast cell membranes, resulting in the release of free fatty acids into the beer samples (Rodriguez-Vargas et al. 2007). Also, at 30ºC fermentations, yeast cell density may have been lost due to autolysis and could have resulted in an increase in free fatty acid concentrations in the beer because of solubilisation of membrane lipids, thus resulting in lower foam head stability. It has been previously reported that the presence of lipids or free fatty acids in beer could lead to a decrease in beer foam head stability (Dickie et al. 2001; Van Nierop et al. 2004).Fig. 2 Colour profiles (a) and clarities (b) of beer produced by different yeast strains under varying fermentation conditions. Values are average from six values ± standard deviation.Fig. 3 Foam head stability of beer produced by the different strains at varying fermentation temperatures. Values are average from six values ± standard deviation.Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density Beer volatile compounds and organoleptic quality assessmentThe relative percentages of the important volatile compounds detected in the beer samples are indicated in Table 1. Higher alcohol, isoamyl alcohol, constituted a large percentage of the BVCs in most samples, constituting up to 49% of the total BVCs in beer samples produced with strain B at room temperature fermentation. Most of the other compounds constituted below 15% of the total BVCs, however, isoamyl acetate constituted approximately 30% of the BVCs in the control sample and between 8.345-17.712% and 8.382-10.247% of the total BVCs in beer produced with strain A and B, respectively, at the different temperatures. Furthermore, ethyl caproate constituted roughly 10% or more of the volatiles found in all samples, while 2-phenylethyl acetate constituted between 4% and 7% in most samples except for the control, and beer samples produced at 22.5ºC where it constituted greater than 10% of the total BVCs (Table 1). GC-MS chromatogram of beer samples showing the different peaks representing the BVCs detected is shown in Figure 4. The seven volatile compounds detected in the beer samples produced in this study have also been found in beer produced from a previous study (Kopsahelis et al. 2007).quality of the different beer samples. As represented in Figure 5, about 35% of the samplers felt that the beers produced had a moderate sour apple taste. This taste profile is usually characteristic of the flavour, volatile esters; ethyl caprylate and ethyl caproate (Verstrepen et al. 2003). Also, roughly 65% of the samplers felt that all beers produced had a moderate warm mouth-feel and this characteristic is generally attributed to the presence of ethanol produced from fermentation as well as the presence of fusel alcohols (Ter Schure et al. 1998). Roughly 40% of samplers felt that a moderate medicinal aroma was present in beers produced at the 22.5ºC and 30ºC fermentations using strain A as well as the room-temperature fermentation for strain B. Generally, these characteristics are attributed to the presence of volatile phenolic compounds in beers (Vanbeneden et al. 2008), while the moderate solvent aroma felt by the samplers in some of the beers is usually attributed to the presence of ethyl acetate (Verstrepen et al. 2003). The non-detection of phenolic compounds could explain the general moderate medicinal smell feelings by most of the samplers. Perhaps, some of these compounds were not present in these beer samples since their generation depends on the activities of the yeast (Peddie, 1990; Brown and Hammond, 2003) as well as the composition of the wort (Kobayashi et al. 2008). Alternatively, the lack of detection could be attributed to limitation of the methods used for the analysis. Previous studies by Saison et al. (2008) and Pinho et al. (2006) have shown that fibres used for headspace analysis are efficient for detection of different classes of volatiles in beer. Thus, it is possible that the Tenax and Carbotrap fibres used in this analysis lacked the affinity required to detect some of the volatiles in the beer. This is a subject of further investigation in our laboratory.Olaniran et al.The percentage of samplers that agreed that specfic flavour or aroma characteristics were present in moderate levels in beers produced by different yeast strains at different fermentation temperatures.Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density CONCLUDING REMARKSResults from this study have shown that different yeast strains and fermentation temperatures affects beer quality, especially turbidity, foam head stability, spent yeast density and yeast viability. However, these parameters had not much effect on the colour profiles of the beers produced and no effect on the qualitative properties of volatiles produced but rather on the relative quantities of the BVCs as evident in the headspace GC-MS analysis. However, in order to increase accuracy of volatile detection, it would be prudent to investigate the effect of the different headspace trapping fibres on detectable BVCs profile. The presence of varying concentrations of BVCs appeared to affect the organoleptic properties of the beer; however, the employment of qualified beer samplers is required to provide a more accurate view. Further optimization is required to determine the effects of other fermentation parameters on overall beer quality as well as investigate gene expression profiles by the different yeast strains under the different fermentation conditions.Financial support:This study was supported by the South African Breweries and Competitive Research Grant of the University of KwaZulu-Natal, Durban, South Africa.REFERENCESBARDI, E.P.; KOUTINAS, A.A.; SOUPIONI, M.J. and KANELLAKI, M.E. (1996a). Immobilization of yeast on delignified cellulosic material for low temperature brewing. Journal of Agricultural and Food Chemistry, vol.44, no. 2, p. 463-467. [CrossRef]BARDI, E.P.; SOUPIONI, M.; KOUTINAS, A.A. and KANELLAKI, M. (1996b). Effect of temperature on the formation of volatile by-products in brewing by immobilized cells. Food Biotechnology, vol. 10, no. 3, p. 203-217.[CrossRef]BARDI, E.; KOUTINAS, A.A. and KANELLAKI, M. (1997). Room and low temperature brewing with yeast immobilized on gluten pellets. Process Biochemistry, vol. 32, no. 8, p. 691-696. [CrossRef] BEKATOROU, A.; SARELLAS, A.; TERNAN, N.G.; MALLOUCHOS, A.; KOMAITIS, M.; KOUTINAS, A.A. and KANELLAKI, M. (2002). Low-temperature brewing using yeast immobilized on dried figs. Journal of Agricultural and Food Chemistry, vol. 50, no. 25, p. 7249-7257. [CrossRef]BLIECK, L.; TOYE, G.; DUMURTIER, F.; VERTSTREPEN, K.J.; DELVAUX, F.R.; THEVELEIN, J.M. and VAN DIJCK, P. (2007). Isolation and characterization of brewer's yeast variants with improved fermentation performance under high-gravity conditions. Applied and Environmental Microbiology, vol. 73, no. 3, p. 815-824. [CrossRef]BROWN, A.K. and HAMMOND, J.R.M. (2003). Flavour control in small-scale beer fermentations.Food and Bioproducts Processing, vol. 81, no. 1, p. 40-49. [CrossRef]BURKUS, Z. and T EMELLI, F. (2000). Stabilization of emulsions and foams using barley β-glucan. Food Research International, vol. 33, no. 1, p. 27-33. [CrossRef]CORTACERO-RAMIREZ, S.; DE CASTRO, M.H.B.; SEGURA-CARRETERO, A.; CRUCES-BLANCO, C. and FERNANDEZ-GUTIERREZ, A. (2003). Analysis of beer components by capillary electrophoretic methods.TrAC Trends in Analytical Chemistry, vol. 22, no. 7, p. 440-455. [CrossRef]DICKIE, K.H.; CANN, C.; NORMAN, E.C.; BAMFORTH, C.W. and MULLER, R.E. (2001). Foam negative materials.Journal of the American Society of Brewing Chemists, vol. 59, no. 1, p. 17-23. [CrossRef]EICHER, S.D.; McKEE, C.A.; CARROLL, J.A. and PAJOR, E.A. (2006). Supplemental vitamin C and yeast cell wall β-glucan as growth enhancers in newborn pigs and as immunomodulators after an endotoxin challenge after weaning. Journal of Animal Science, vol. 84, no. 9, p. 2352-2360. [CrossRef]HANSEN, J. (1999). Inactivation of MXR1 abolishes formation of dimethyl sulfide from dimethyl sulfoxide in Saccharomyces cerevisiae. Applied and Environmental Microbiology, vol. 65, no. 9, p. 3915-3919. KOBAYASHI, M.; SHIMIZU, H. and SHIOYA, S. (2008). Beer volatile compounds and their application to low-malt beer fermentation. Journal of Bioscience and Bioengineering, vol. 106, no. 4, p. 317-323. [CrossRef] KOPSAHELIS, N.; KANELLAKI, M. and BEKATOROU, A. (2007). Low temperature brewing using cells immobilized on brewer’s spent grains. Food Chemistry, vol. 104, no. 2, p. 480-488. [CrossRef]KUIPER, S.; VAN RIJN, C.; NIJDAM, W.; RASPE, O.; VAN WOLFEREN, H.; KRIJNEN, G. and ELWENSPOEK, M.(2002). Filtration of lager beer with microsieves: Flux, permeate haze and in-line microscope observations.Journal of Membrane Science, vol. 196, no. 2, p. 159-170. [CrossRef]NAGODAWITHANA, T.W.; CASTELLANO, C. and STEINKRAUS, K.H. (1974). Effect of dissolved oxygen, temperature, initial cell count and sugar concentration on the viability of Saccharomyces cerevisiae in rapid fermentations. Applied and Environmental Microbiology, vol. 28, no. 3, p. 383-391.PEDDIE, H.A.B. (1990). Ester formation in brewery fermentations. The Journal of the Institute of Brewing and Distilling, vol. 96, no. 5, p. 327-331.PINHO, O.; FERREIRA, I.M.P.L.V.O. and SANTOS, L.H.M.L.M. (2006). Method optimization by solid-phase microextraction in combination with gas chromatography with mass spectrometry for analysis of beer volatile fraction. Journal of Chromatography A, vol. 1121, no. 2, p. 145-153. [CrossRef]。
酵母菌发酵实验设计
酵母菌发酵实验设计English Answer:The experiment on yeast fermentation can be designed as follows:1. Purpose: To investigate the effect of different sugar concentrations on yeast fermentation.2. Materials:Yeast culture.Different sugar solutions (e.g., glucose, fructose, sucrose)。
Water.Test tubes.Thermometer.Stopwatch.3. Procedure:a. Prepare different sugar solutions with varying concentrations. For example, prepare solutions with 5%, 10%, and 15% sugar concentrations.b. Label the test tubes accordingly.c. Add equal amounts of yeast culture to each test tube.d. Add the respective sugar solution to each test tube, ensuring that the sugar concentration is consistent.e. Mix the contents of each test tube gently.f. Place the test tubes in a warm environment (around 37°C) and start the stopwatch.g. Observe the fermentation process by noting the formation of bubbles or gas production.h. Record the time it takes for each sugar concentration to show signs of fermentation.i. Repeat the experiment multiple times to ensure accuracy and reliability of the results.j. Analyze the data collected and draw conclusions regarding the effect of sugar concentration on yeast fermentation.中文回答：酵母发酵实验可以设计如下：1. 目的，研究不同糖浓度对酵母发酵的影响。
发酵酸奶 实验报告
发酵酸奶实验报告英文回答：Fermented yogurt is a popular dairy product that is enjoyed by people all over the world. It is made through a process called fermentation, where specific bacteria, such as Lactobacillus bulgaricus and Streptococcus thermophilus, are added to milk. These bacteria convert the lactose in the milk into lactic acid, which gives yogurt its tangy taste and thick texture.To conduct an experiment on fermenting yogurt, you will need a few ingredients and equipment. Firstly, you will need fresh milk, preferably whole milk, as it provides a creamier texture. You will also need a starter culture, which can be store-bought yogurt that contains live active cultures. Additionally, you will need a thermometer to monitor the temperature and a clean container to store the yogurt during fermentation.The first step is to heat the milk to a specific temperature. This is usually around 180°F (82°C). Heating the milk helps to kill any unwanted bacteria and denature the proteins, which helps to thicken the yogurt. Once the milk has reached the desired temperature, it should be cooled down to around 110°F (43°C).Next, a small amount of the starter culture is added to the cooled milk. This introduces the beneficial bacteria that will ferment the milk and turn it into yogurt. The milk and starter culture should be mixed well to ensure even distribution of the bacteria.After mixing, the milk and starter culture mixture should be transferred to a clean container and covered tightly. The container should be placed in a warm location, ideally between 100-110°F (38-43°C), to allow the bacteria to grow and ferment the milk. This process usually takes around 4-6 hours, but it can vary depending on the desired thickness and tanginess of the yogurt.Once the desired fermentation time has passed, theyogurt can be refrigerated to stop the fermentation process. At this point, the yogurt should have a thick and creamy consistency with a tangy flavor. It can be enjoyed as is or flavored with fruits, honey, or other additives accordingto personal preference.中文回答：发酵酸奶是一种受到全球人们喜爱的乳制品。
酵母菌发面蒸馒头感悟
酵母菌发面蒸馒头感悟英文回答：The fermentation process of using yeast to make steamed buns is a fascinating experience. It involves the interaction between yeast, flour, and water to create asoft and fluffy texture in the final product. Through this process, I have gained several insights.Firstly, I have come to appreciate the importance of yeast in the fermentation process. Yeast is a microorganism that feeds on sugar and produces carbon dioxide as a byproduct. This gas is what causes the dough to rise and gives the steamed buns their airy texture. Without yeast, the dough would remain dense and flat. It is incredible to witness how these tiny organisms can transform a simple mixture of flour and water into something so delicious.Secondly, I have learned the significance of time and temperature in the fermentation process. Yeast requireswarmth to thrive, but too much heat can kill it. Therefore, finding the right balance of temperature is crucial. Additionally, allowing the dough to rest for an adequate amount of time is essential for the yeast to fully activate and produce the desired texture. Patience is key in this process, as rushing it can lead to disappointing results.Furthermore, I have realized the importance of proper kneading and shaping techniques. Kneading the dough helps to develop gluten, a protein that gives the steamed buns their structure and elasticity. It is important to knead the dough until it becomes smooth and elastic, as this ensures even fermentation and a uniform texture. Shaping the dough into small, round buns is also crucial for the final presentation. It requires practice and precision to achieve perfectly shaped steamed buns.Lastly, I have discovered the joy of experimenting with different ingredients and flavors. While traditional steamed buns are made with plain flour, water, and yeast, there is room for creativity. Adding ingredients such as milk, sugar, or even savory fillings can elevate the tasteand texture of the buns. It is exciting to explore different combinations and discover unique flavors.中文回答：使用酵母制作发面蒸馒头的发酵过程是一次令人着迷的经历。
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竭诚为您提供优质文档/双击可除酵母菌发酵实验报告英文篇一：发酵实验报告实验报告实验名称：与酵母菌发酵所属课程名称：发酵工程工艺原理班级：20XX级生物技术组长：组员：时间:20XX.11.27—20XX.12.3实验指导教师：黄循吟海南师范大学生命科学学院20XX年12月5日摇瓶的应用与酵母菌发酵摘要：发酵工程属于生物技术的范畴，是指利用微生物的生长繁殖和代谢活动来大量生产人们所需要的产品过程的理论和工程技术体系，是生物工程和生物技术学科的重要组成部分。
本实验通过对酵母菌进行摇瓶培养,并定时取样测定其oD值、ph和菌体数，制作菌体生长曲线，以此判断酵母菌的生长发酵状况。
关键词：发酵、摇床、酵母菌一.目的1.掌握酵母发酵工艺流程及其具体操作方法。
2.了解酵母菌的生长代谢的基本规律。
二．原理千百年来，人类几乎天天离不开酵母菌，例如酒类的生产，面包的制作，乙醇和甘油的发酵，本实验主要通过对酵母菌发酵过程中一些数值的测定，绘制其生长曲线，来了解酵母菌的生长状况。
为获得实验相关数据，需对酵母菌进行培养，首先涂布平板28℃培养48小时后挑取单菌落进行斜面保存，再挑取斜面保存的菌种进行扩大培养，自扩大培养起，每三个小时取一次样，在oD505下测吸光度，在显微镜下观察，计算菌种数量当菌种数量达到108个/ml时（用血细胞计数板计数，以25个中方格的计数板为例，设5个中方格中的总菌数为A，菌液稀释倍数为b，则：1ml菌液中的总菌数=A/5*25*10＾4*b），即可进行发酵培养。
自发酵培养起每三个小时取一次样，测其吸光度值、ph值（用ph计测量）、菌种数量。
结果整理：（1）以时间为横坐标。
oD值为纵坐标作图。
（2）对最终的发酵液进行离心，得湿酵母烘干，称干重，计算得率。
最后对实验结果进行讨论和分析。
三.材料与方法1．实验材料菌种：酵母菌2.培养基配方分离培养基：黄豆芽100g，葡萄糖50g，水100ml，琼脂20g，ph值自然种子培养基：葡萄糖40g，蛋白胨10g，蒸馏水1000ml，ph值自然3．仪器设备分光光度计、旋转式摇床、离心机、冷藏箱、ph计、电子天平、电磁炉等。
4．用具烧杯、三角瓶、量筒、玻璃棒、比色杯、试管、离心管、移液管、接种环、酒精灯、培养皿、滴管、移液枪5．试剂蒸馏水、酒精四．实验步骤与方法1.酵母菌种的分离：1.1分离培养基制备与灭菌：称鲜豆芽100g，放入烧杯中，加水1000ml，煮沸30min，用纱布过滤，用水补足原量，再加入葡萄糖50g，琼脂20g，煮沸溶化，分装三角瓶和试管，包扎，在121℃下灭菌20分钟。
1.2菌种的保存:取酵母粉1g，加10ml无菌水制成菌悬液，并按梯度10﹣1、10-2、10-3进行稀释。
分别取0.2ml涂布平板，在28℃培养48小时，挑单菌落于斜面试管在28℃培养48小时，备用。
2.菌种扩大培养：用接种环挑两环保存在斜面试管上的菌种，放入150ml 的三角瓶(每瓶含有75ml的种子培养液)中进行扩大培养，150r/min,28℃摇瓶培养48小时。
3.发酵培养：将扩大培养后的菌液按10%的接种量接到250ml的三角瓶中进行摇床培养，即取20ml菌种液置于200ml的种子培养液中，150r/min,28℃培养48小时，同扩大培养一样，每三个小时取一次样，测其吸光度值、ph值和菌种数量。
4.数据整理，绘制曲线：以时间为横坐标，分别以菌液浓度，ph，oD值为纵坐标作图。
5.计算得率：发酵完毕，取出摇瓶内培养基装入离心管，离心分离，得湿酵母烘干，称干重，计算得率。
1.扩培过程数据结果1.1每3小时记录一次扩培过程中菌液的ph值、oD505、菌液浓度，结果如表1：表1扩培过程各参数值时间扩配时间h01:0004:0007:0010:0013:0016:0019:0022:0001:0004:000 7:0010:0013:0016:0019:0022:0036912151821242730333639424548282828282828282828282828282828280.1820.5890.7231.3951.7312.0532.2232.1572.1532.1812 .1732.1282.1572.1521.9731.355温度℃oD505菌液浓度（个/ml）2.56×1042.82×1064.20×1075.64×1077.05×1078.25×1072.82×1083.07×1083.33×1084.15×1084.27×1085.12×1085.63×1086.32×1086.65×1087.25×108ph值5.274.974.624.314.324.354.454.444.364.294.324.414.2 94.334.384.36转速r/min1501501501501501501501501501501501501501501501 50取样mL10101010101010101010101010101010篇二：酵母菌酒精发酵实验报告实验方案酵母菌酒精发酵的条件研究学院（部）：生物与化学工程学院专业：生物工程学生姓名：鑫学号：11018150班级：生物工程二班指导教师：肖一、实验目的1、学会实验的设计和操作过程2、找到酵母菌发酵时的最优条件二、培养基和实验方法及材料的确定1、玉米粉的糖化方法玉米粉的糖化采用双酶法，其工艺流程如下玉米粉→加水→液化→糖化→发酵→蒸馏→成品酒精试验中，发酵培养按照三角瓶100ml培养。
本次工做20组是要，共需发酵液20*100=2000ml。
培养液按照100g玉米粉、300ml水。
所以共需玉米粉700g。
液化：取１００ｇ玉米粉，加入３００ｍＬ的水，液化温度为９０℃，ｐＨ值为５．５，液化时间为３．５ｈ，液化酶的添加量为０．０３５ｇ／１００ｇ玉米粉糖化：糖化时的工艺条件为：糖化温度为５８℃，ｐＨ值为４．５，糖化时间为３．５ｈ，糖化酶的添加量为０．３ｇ／１００ｇ玉米粉。
2、活化培养基本实验在进行实验时采用察氏(czapck)培养基的配制，配方如下表一：表一3、扩大培养基扩大培养仍然用察氏(czapck)培养基，由于要用液体的，所以将其中的琼脂配料去掉。
4、发(:酵母菌发酵实验报告英文)酵培养基糖化液稀释至l0%浓度，添加辅料（硫酸铵0.4%），ph5.5灭菌三、培养基的制备及酵母的活化1、准备酵母母菌一支常温下存放一天，增加菌种的活力。
在母菌存放期间制作各时期培养基2、准备固体培养基（察氏培养基）50ml，做成8支试管斜面，扩大培养基800ml（做扩大培养时使用）。
做成8个三角瓶，每瓶200ml。
120℃灭菌30min。
3、发酵液的制备（1）玉米粉的筛选实验前准备粉碎后的玉米粉700g。
（2）玉米粉的液化按照100g玉米粉、300ml水的配比对玉米粉进行液化，液化方案上文已经交代。
在1000ml烧杯里，或者500ml烧杯分两次，水浴液化。
器材：烧杯500ml两个，玻璃棒一个，水浴锅一个，糖化酶0.225g步骤：1、将糖化酶，玉米粉，水按照比例配置好在烧杯里。
2、将配好的玉米液放于水浴锅中90℃液化3.5h。
边液化边搅拌。
（3）玉米粉的糖化将液化后的玉米液中按照0.3g/100ml加入液化液中。
再在水浴锅中，58℃糖化3.5h。
（4）过滤糖化后的糖化液有可能有没有彻底液化的玉米颗粒，会造成浑浊，这时需要对糖化液进行过滤操作。
操作步骤：最后与以上培养基一起进行灭菌处理。
灭菌时，清洗16支移液管，与培养基一起灭菌。
（5）活化步骤器材：酒精灯，接种针，母菌，斜面培养基，消毒酒精。
步骤：1、将器材放于实验台上。
对双手合桌面进行灭菌。
对接种针进行灼烧灭菌。
2、在酒精灯旁按照无菌操作步骤在酒精灯火焰旁取下试管棉塞。
3、将灼烧后的接种针伸入母菌试管取粘取少量母菌，粘取前将接种针放于试管内壁，冷却5~6s。
4、按照无菌操作将取过母钟的接种针移入活化试管内并画曲线。
5在酒精灯火焰旁将试管棉塞塞上，塞前将棉塞烧一下。
如此接种八支试管。
并保存28℃培养2d。
四、酵母的扩大培养器材：液体培养基，活化后菌种，酒精灯，接种针，消毒酒精。
步骤：1、将器材放于试验台上，并对双手和桌面灭菌，接种针进行灼烧灭菌。
2、在酒精灯旁取下棉塞，并用接种针接种少量菌种于液体培养基内。
3、在酒精灯旁塞好棉塞，并于28℃培养。
根据发酵单因素的不同，确定培养时间。
其中变量是菌龄的一瓶瓶号1、2要求培养时间分别为：对数期1：15~16h，对数期2:16~18h，缓冲期：20~24h，稳定期：24~26h。
其他菌种培养20h进行接种。
五、发酵培养1、不同菌龄下的发酵器材：扩大菌种的四个不同阶段即对数期1：15~16h，对数期2:16~18h，缓冲期：20~24h，稳定期：24~26h。
移液管四个，酒精灯，发酵液，洗耳球。
步骤：1、将对数期1的菌种和其他设备放于实验台上。
2、用移液管按照发酵液的10%的比例移取扩大培养液到发酵液中。
3、塞好棉塞将发酵液放于30℃条件下培养2d。
4、按照以上步骤将不同菌龄的扩大菌种移接到发酵液中进行发酵培养。
之后进行酒精检测。
2、不同菌量下的发酵器材：扩大菌种，移液管四个，酒精灯，发酵液，洗耳球。
步骤：1、将实验器材放于实验台上。
2、用移液管移取8%的扩大菌种到发酵液中。
3、塞好棉塞，将发酵液存放于30℃条件下发酵2d。
4、按照以上步骤，分别移取10%、12%、14%的扩大菌种到发酵液中，30℃培养2d，之后进行酒精检测。
3、不同醪液浓度下的发酵器材：扩大菌种，移液管四个，酒精灯，发酵液，洗耳球。
步骤：1、将实验器材放于实验台上。
2、用移液管移取10%的扩大菌种到4个发酵液中。
3、制作不同浓度的醪液，分别按照1:2,1:3,,1:4，1:5。
3、塞好棉塞，将四个发酵液三角瓶编号1、2、3、4。
将发酵液按照序号存放于30℃条件下发酵2d。
4、对发酵后的发酵液进行酒精检测。
4、不同发酵时间下的发酵器材：扩大菌种，移液管四个，酒精灯，发酵液，洗耳球。
步骤：1、将实验器材放于实验台上。
2、用移液管移取10%的扩大菌种到4个发酵液中。
3、塞好棉塞，将发酵液将四个发酵液三角瓶编号1、2、3、4。
存放于30℃条件下发酵。
按照序号分别培养2d、2.5d、3d、3.5d。
4、对发酵后的发酵液进行酒精检测。
六、酒精检测器材：蒸馏设备一套，200ml量筒4个，酒精检测器一个，步骤：1、将100ml发酵液配制成200ml溶液于蒸馏烧瓶中。
2、对200ml发酵液进行蒸馏，蒸馏出100ml酒精溶液。