FermentationUsman HaiderRoll # 3323

What is fermentation?Fermentation is a metabolic process in which an organism converts a carbohydrate, such as starch or a sugar, into an alcohol or an acid. For example, yeast perform fermentation to obtain energy by converting sugar into alcohol. Bacteria perform fermentation, converting carbohydrates into lactic acid.

History of fermentation?Fermentation is a natural process. People applied fermentation to make products such as wine, mead, cheese and beer long before the biochemical process was understood. In the 1850s and 1860s Louis Pasteur became the firstzymurgistor scientist to study fermentation when he demonstrated fermentation was caused by living cells.

Types of fermentaion?Aerobic Fermentation

Aerobic fermentation means that oxygen is present. Wine, beer and acetic acid vinegar (such as apple cider vinegar), need oxygen in the primary or first stage of fermentation. Anaerobic FermentationAnaerobic fermentaion means that oxygen is absent. It is of two types.Ethanol fermentation Ethanol fermentation is the process by which yeast and some types of bacteria convert sugar into alcohol and carbon dioxide. This process is used for making bread and producing alcoholic beverages such as beer, wine and hard cider.

C6H12O6(glucose) 2 C2H5OH (ethanol) + 2 CO2(carbon dioxide) Ethanol fermentation is used the production of beer, wine and bread. It's worth noting that fermentation in the presence of high levels of pectin result in the production of small amounts of methanol, which is toxic when consumed. One common nonalcoholic beverage that isproduced via the fermentation process is tea. After the green leaves of the Camellia sinensis plant are steamed and dried, they are fermented, modifying the flavor

2. Lactic acid fermentaion The pyruvate molecules from glucose metabolism (glycolysis) may be fermented into lactic acid. Lactic acid fermentation is used to convert lactose into lactic acid in yogurt production. It also occurs in animal muscles when the tissue requires energy at a faster rate than oxygen can be supplied. C6H12O6(glucose) 2 CH3CHOHCOOH (lactic acid) The production of lactic acid from lactose and water may be summarized as: C12H22O11(lactose) + H2O (water) 4 CH3CHOHCOOH (lactic acid)

Two types of lactic acid fermentationhomolactic fermentationis the production of lactic acid exclusively

heterolactic fermentationis the production of lactic acid as well as other acids and alcohols

Microbes responsible for fermentation Saccharomyces: ethyl alcohol and carbon dioxide

Streptococcus and lactobacillus: lactic acid

Escherichia coli: Acetic acid and succinic acid

Clostridium : butyric acid, butyl alcohol and acetone.

Fermentaion productsMost people are aware of food and beverages that are fermentation products, but may not realize many important industrial products results from fermentation.

beer wine yogurt cheese certain sour foods containing lactic acid, including sauerkraut, kimchi and pepperoni bread leavening by yeast

sewage treatment some industrial alcohol production, such as for biofuels hydrogen gas

Production of yoghurt by fermentation Yogurt is produced through the fermentation of milk by lactic acid bacteria, usuallylactobacillus bulgariusand Streptococcus thermophilus The milk is firstly heat treated, homogenised and is then cooled to allow the addition of bacteria or starter culture. Given the right conditions, i.e. correct temperature and moisture, the bacteria are able to ferment the milk sugar (lactose), producing lactic acid. The milk proteins then coagulate and set, to form yogurt.

Yogurt can be made from different types of milk, including skimmed, semi-skimmed, whole, evaporated or powdered forms. A colourless liquid called acetaldehyde is also produced during fermentation and gives yogurt its distinct flavour.

Production of bread by fermentation In bread making fermentation is a fundamental process carried out by special kind of yeast. Once the bread is mixed it is then left to rise (ferment). As fermentation takes place the dough slowly changes from a rough dense mass lacking extensibility and with poor gas holding properties, into a smooth, extensible dough with good gas holding properties. In the process of fermentation, yeast produces carbon dioxide, alcohol and other compounds which enable dough to rise and modify its physical properties.

Together with alcohol, a small amount of other volatile compounds are released. These are involved in the original taste and flavors of baked leavened products. Most of these compounds, and all of the alcohol, evaporate when baked. There are two stages during the fermentation of a dough made from flour, water, salt and yeast, and with no extra sugar added. First of all, yeast ferments sugars naturally present in flour, which can be directly and easily assimilated. These sugars represent about 1.5% of the flour weight. At the end of this first stage, gaseous releases more or less slow down. First stage

Second stageThe second stage corresponds to the fermentation of a sugar contained in flour called maltose. Maltose comes from the action of some enzymes, the amylases, on the starch granules of the flour. Amylases which are naturally present in flour, split starch into small fractions of a much simpler sugar, the maltose. The action of amylases starts as soon as water is added to the flour and stops during baking. 2. The action of the flour amylases is completed by that of another enzyme of yeast, the maltase which, in its turn, splits maltose to give the most simple sugar, glucose. The glucose is transformed by the yeast into carbon dioxide and alcohol

3. Maltose formed from starch must be present in sufficient quantity so that the production of carbon dioxide makes dough rise correctly until it is put in the oven Use of yeast For bread making, the amount of yeast used is between 2 and 5 kilos of compressed yeast for 100 kilos of flour. A standard amount of 2.5 grams of bakers yeast for 100g of flour provides 25 billion yeast cells. This is the proof that bakers yeast is predominant in the bakery fermentation.

Fermentation Fermentation begins as soon as the yeast is in contact with the mixture of water and flour. During the first fermentation (bulk fermentation), the baker lets the dough rise for a first time. During that stage, the physical properties of the dough (extensibility and elasticity) are modified, thus completing the kneading action. The mechanisation of the division of the dough requires some rest so that the dough pieces may relax before moulding, in order to recover some extensibility.

The fermentation process goes on in the cut lumps of dough during the proofing which can be made on layers, on flexible nets or in moulds, in cupboards at ambient temperature or in proofing ovens. In order to prevent the lumps of dough drying out during this stage, they must be covered so as not to hinder the development and the appearance of the finished product.

Production of cheese by fermentationCheese is way of preserving milk for long periods of time. In the process, the milk in cheese becomes something completely unlike milk, but cheese has its own interesting and delicious properties. Cheese-making is a long and involved process that makes use of bacteria,enzymesand naturally formedacidsto solidify milk proteinsandfatand preserve them. Once turned into cheese, milk can be stored for months or years.

Production of hard cheesesThe basic principles involved in cheese manufacture have remained the same for over 1000 years.The milk is firstly heat treated to kill off any harmful bacteria that may be present. Starter cultures of special bacteria are then added to the milk and their growth ripens the milk and helps to develop the desired flavours and aromas.Rennet is then added to the milk which helps it to coagulate and turn into curds and whey. Rennet was traditionally extracted from calves stomachs, but is now artificially produced from vegetarian sources.The curds and whey are then heated to a high temperature and salt is added to produce the correct texture and flavour.The cheese is then pressed to force out the whey, and to give it its final shape. The cheese is then left to mature and the longer the cheese is left in storage the more mature the flavour becomes.

As you can see, cheese-making is complicated. It produces a product that preserves milk proteins and sugars with acids and salt. Production of soft cheeseSoft cheeses fall intotwo categories: ripened e.g. brie and fresh (unripened) e.g. cottage cheese.Soft cheeses are made from heat treated milk which is fermented by the use of specific bacteria.Artificial rennet is sometimes used to produce a firmer texture.Fresh cheeses are ready for use as soon as the manufacturing process is complete but ripened cheeses are allowed to mature in temperature and humidity controlled rooms for up to one month.

Production of wine by fermentationInitial Stages(For All Wines)Once the grapes have been picked and transported to the winery, certain preparatory steps must be taken before the actual winemaking can begin.Cleanliness and sanitation are essential for good winemaking, as troublesome bacteria can cause disastrous results.Equipment must be sanitized with an O2 based caustic solution, rinsed with water, and finally treated with an anti-bacterial sulfite solution.Upon arriving at the winery, grapes are treated with 50-75 ppm of free sulfur dioxide.This process is called sulfating, and inhibits the unwanted microorganisms and wild yeast species on the grapesPressing the grapesGrapes that are meant for the production of white wine are picked and immediatelyprocessed in the winepress.The grapes are gently squeezed for about 2 hours and the juice is pumped (or fed by gravity) into holding tanks.In the tanks, the juice is chilled, and sediment from the fruit drops to the bottom. The sediments are removed and wine is ready to be fermented with yeast

The juice is transferred to fermenting vats, and the yeast is added With the addition of yeast, the term wine can now be used to describe the grape juice. The species of yeast that is used to ferment grape juice into wine isSaccharomyces cerevisiae.The juice is put in large vats from which air is excluded.In this way, oxidation is prevented and the growth of bacteria is discouraged.The most problematic bacterium is of the genus Acetobecter.This organism has the potential to convert wine into vinegar overnight.Fortunately,Acetobecteris sensitive to free sulfur dioxide and preventative measure against the bacteria can be taken .Fermentation is a process that takes place slowly over a period of ten to thirty days.The temperature of the liquid is maintained at approximately 25oC, as severe changes in temperature can kill the necessary yeast cells.Certain types of wines are fermented in ways that give them their characteristic flavors.For example, Chardonnay is placed in oak barrels to ferment, and an oaky flavor in the final wine product resultsFermentation

Malo-lactic FermentationOak fermented wines may go through secondary fermentation, called malo-lactic fermentation.This is a reaction in which malic acid is converted into lactic acid, and results in the texture of the wine changing from crisp and light to creamier buttery .Malo-lactic fermentation can either be introduced, or may naturally occur.It is not an easily predicted reaction: it may begin immediately, or it may take months for the process to begin.The progress of malo-lactic fermentation is monitored with paper chromatography.The benefits of secondary fermentation are that it reduces the amount of total acidity and causes a mellowing of the tartness in the wineAgingThe amount of time that a wine is aged is equal to the time that elapses between fermentation and drinking.White wine tends not to be aged for long, though some complex white wines can be aged for 3-7 years.Separation, Chilling, and BottlingAfter fermentation, the wine is drawn off to separate it from the dead yeast cells and other sediments that have precipitated from the juice.The wine is chilled to create more clarification, and then bottled.

Usman HaiderRoll # 3323Ethanol fermentation is the process by which yeast and some types of bacteria convert sugar into alcohol and carbon dioxide. This process is used for making bread and producing alcoholic beverages such as beer, wine and hard cider. One common nonalcoholic beverage that isproduced via the fermentation process is tea. After the green leaves of the Camellia sinensis plant are steamed and dried, they are fermented, modifying the flavorLactic acid fermentaionC12H22O11(lactose) + H2O (water) 4 CH3CHOHCOOH (lactic acid) homolactic fermentationis the production of lactic acid exclusivelyheterolactic fermentationis the production of lactic acid as well as other acids and alcoholsSaccharomyces: ethyl alcohol and carbon dioxideStreptococcus and lactobacillus: lactic acidEscherichia coli: Acetic acid and succinic acidClostridium : butyric acid, butyl alcohol and acetone,beerwineyogurtcheesecertain sour foods containing lactic acid, including sauerkraut, kimchi and pepperonibread leavening by yeastsewage treatmentsome industrial alcohol production, such as for biofuelshydrogen gas

Yogurt is produced through the fermentation of milk by lactic acid bacteria, usuallylactobacillus bulgariusandStreptococcus thermophilus In the process of fermentation, yeast produces carbon dioxide, alcohol and other compounds which enable dough to rise and modify its physical properties. First stageThe action of the flour amylases is completed by that of another enzyme of yeast, the maltase which, in its turn, splits maltose to give the most simple sugar, glucose. The glucose is transformed by the yeast into carbon dioxide and alcoho A standard amount of 2.5 grams of bakers yeast for 100g of flour provides 25 billion yeast cells. This is the proof that bakers yeast is predominant in the bakery fermentation. AThe mechanisation of the division of the dough requires some rest so that the dough pieces may relax before moulding, in order to recover some extensibility. The fermentation process goes on in the cut lumps of dough during the proofing which can be made on layers, on flexible nets or in moulds, in cupboards at ambient temperature or in proofing ovens. In order to prevent the lumps of dough drying out during this stage, they must be covered so as not to hinder the development and the appearance of the finished product. Cheese is way of preserving milk for long periods of time. In the process, the milk in cheese becomes something completely unlike milk, but cheese has its own interesting and delicious properties. Cheese-making is a long and involved process that makes use ofbacteria,enzymesand naturally formedacidsto solidify milkproteinsandfatand preserve them. Once turned into cheese, milk can be stored for months or years. The curds and whey are allowed to soak until the lactic acid bacteria create a lactic acid concentration that is just right. At that point, the whey is drained off and salt is added.

As you can see, cheese-making is complicated. It produces a product that preserves milk proteins and sugars with acids and salt. Fermentation