What is an experiment? It is a test using scientific methods to discover how someone or something reacts under certain conditions.

Transcription

1 8. PASTEURIZATION LEAD-IN What is an experiment? It is a test using scientific methods to discover how someone or something reacts under certain conditions. Task 1 Decide which of the following expressions is not correct To carry out an experiment To make an experiment To conduct an experiment To do an experiment To perform an experiment Task 2 How much do you know about Louis Pasteur? Share your knowledge with other students. However successful you have been in answering this question, you should check your knowledge by reading the following text. LOUIS PASTEUR ( ) When meditating over a disease, I never think of a remedy for it, but instead, a means of preventing it. Louis Pasteur, a French chemist, is noted for his studies of fermentation and bacteria. He disproved the theory of spontaneous generation and advanced the germ theory of infection. His discovery that most infectious diseases are caused by germs, known as the germ theory of disease, is one of the most important in medical history. His work became the foundation for the science of microbiology, and a cornerstone of modern medicine. Of great economic importance is the process of pasteurization, which he developed. He is also well-known for his discovery of anthrax and rabies vaccines. In 1888 the Pasteur Institute was founded in Paris, with Pasteur as director, to provide a teaching and research center on virulent and contagious diseases. Each discovery represents a link in an uninterrupted chain, beginning with molecular asymmetry and ending with his rabies prophylaxis, by way of his research in fermentation, wine and beer diseases, asepsis and vaccines.

2 READING Task 1 Task 2 Task 3 What do you know about pasteurization? Write down as many facts as you can in two minutes. Compare and share your notes with your partner. Write down one thing that you want to find out about pasteurization. Look through the text to see if your question is answered. DEVELOPMENT OF THE PASTEURIZATION PROCESS Most people are familiar with pasteurized milk but perhaps few realize that the process of pasteurization was originally developed to preserve wine and beer rather than milk. It is only in the 20 th century that the public water supplies in large cities became really safe to drink. In the 19 th century many people in Europe drank weak beer because it was safer than water. They did not realize that the beer was safe largely because the water used in its manufacture was boiled. As a result, most of the germs that lived in it were killed. Pasteur was asked to investigate the diseases afflicting wine which were causing considerable economic losses to the wine industry. He went to a vineyard in Arbois in 1864 to study this problem. Pasteur began his research by testing the theories of other scientists on the subject. After careful examination of hundreds of samples, he came to the conclusion that the type of decomposition that turned beer sour and food bad was caused by microscopic living organisms that were always present in the air. His theory was not accepted at once. Pasteur delivered the fatal blow to the doctrine of spontaneous generation, the theory held for 20 centuries that life could arise spontaneously in organic materials. He proved that all living organisms, no matter how small, were formed from other living organisms. Pasteurization is the process of heating a liquid, particularly milk, to a temperature between 55 0 C and 70 0 C to destroy harmful bacteria without materially changing the composition, flavour, or nutritive value of the liquid. Louis Pasteur devised this process in 1865 to inhibit fermentation of wine and milk. Milk is pasteurized by heating at a temperature of chic for 30 minutes, rapidly cooling it, and then storing it at a temperature below 1O 0 C. Beer and wine are pasteurized by being heated at about 60 0 C for about 20 minutes. A newer method involves heating at 70 0 C for about 3 seconds and filling the container under sterile conditions. Task 1 Scan the text to find answers to the following questions : 1. Why was the pasteurization process originally developed? 2. Why was beer safer to drink than water in many European cities in the 19 th century? 3. What conclusions did Pasteur come to after conducting his investigation of the problem? 4. Were Pasteur's theories accepted at first? 5. What is the pasteurization process for liquids?

3 WORD STUDY Task 1 Condense these definitions to one word. All your answers are words that are used in the previous passage. E.g. to plan or invent a way of doing something, especially sth. complicated = to develop 1. a belief or set of beliefs that form the main part of a religion or system of ideas 2. knowing a thing well 3. a very tiny animal or plant that causes diseases 4. a small part showing the quality of the whole 5. to make someone suffer or experience serious problems 6. a piece of land where vines are grown in order to produce wine 7. the particular taste of a food or drink 8. a process of inoculating people with a particular preventive agent Task 2 Fill in: VERB decompose preserve inhibit involve store deliver NOUN conclusion pasteurization investigation LANGUAGE SECTION Can, should and must + the passive voice Should and must are frequently used when giving instructions and explaining something is done. Thus, they are often used as an alternative to the imperative. Task 1 Change each imperative to should or must + the passive voice E.g. Do not place hot glass on the bench. Hot glass must not be placed on the bench. 1. Clean all equipment after use. 2. Wear safety glasses in the laboratory. 3. Do not use equipment that is clucked or broken. 4. Wash your hands after you handle chemicals. 5. Add the acid to the water not the other way around.

4 6. Switch off the electricity before you change the light bulbs. 7. Record the results accurately after observing the results of experiments. Task 2 Change each imperative sentence to the interrogative form. E.g. Repeat the experiment three times. Should the experiment be repeated three times? 1. Wash the equipment with soap, water and a brush. 2. Invert the glassware after washing it. 3. Rinse off the soap with lots of water. 4. Report any injury immediately to the instructor. 5. Carry out all instructions concerning an experiment carefully. 6. Record data immediately after you obtain it Task 3 Complete sentence /b/ to give it the same meaning as sentence /a/. E.g a/ It is necessary not to boil the liquid. b/ The liquid need not be boiled. a/ It is important to wear safety glasses in the laboratory. b/ a/ It is not necessary to heat the substances to start the reaction. b/ Task 4 Make passive sentences. Re-arrange the words to make the correct word order. Note that the verb given needs to be adapted. E.g. On/must/place/hot glass/bench/a/laboratory/not Hot glass must not be placed on a laboratory bench. 1. every/ the/ should/ record/ temperature/ the/ minutes/ five 2. of/ oxygen water/ hydrogen compose/ and 3. aids/ yet/ has/ vaccine/ against/ been/ developed 4. there/ some/ doubts/ an/ ideal/ that/ vaccine/ can/ create 5. use/ this/ method/ since/ the/ century/ nineteenth Task 5 Rewrite the sentences and turn them into the passive voice. 1. Students will carry out the experiment in the lab under carefully controlled conditions. 2. Scientists had long waited for the new edition of the textbook. 3. The author dealt with various aspects of the theory. 4. They gave the new element the name of a famous scientist. 5. Scientists often give newly produced substances names that are to show their properties.

5 Task 6 The structure of the passage GROUP WORK Divide into smaller groups and write a summary of the basic text: The development of the pasteurization processes. Compare your summary with the summaries of other groups. Which do you like most? Summarize each of the paragraphs in the following way: E.g. Paragraph 1 introduces the topic of this passage:. Pasteur's development of the process of pasteurization to preserve wine and beer. Paragraph 2 describes, tells the reader about, explains.. WRITING A LABORATORY REPORT Every laboratory report should be provided with: your name the date a reference for the experiment /usually from the textbook/ This initial information should be written at the top of the laboratory report. The essential sections in any laboratory report. There are four sections that must be included in every formal report of a scientific experiment 1. the purpose of the experiment, i.e. why the experiment was done 2. the equipment and the materials that were used 3. the procedure of the experiment 4. the results of the experiment Listening Task 1 Before you listen to the passage, study the questions below. The passage you are going to hear is a description of two experiments that Pasteur conducted. 1. Describe the first experiment that Pasteur carried out. 2. What were the results of his first experiment? 3. What did Pasteur conclude from these resultats?

6 Laboratory report An example of a laboratory report on the first experiment (see above for structure): 1. Purpose To find out where the living organisms in the meat soup come from. 2. Equipment and materials A Bunsen burner and two flasks of clear soup made from meat. 3. Procedure The soup in flask A was boiled for an hour The soup in flask B was not boiled Both flasks were left to stand for a few days The effect of boiling the soup was compared to the effect of not boiling it 4. Results After a few days, organisms formed in both flasks 5. Conclusions The organisms in flask A were carried to the soup by the air. Task 2 Task 3 Listen to the second experiment. Take notes and try to write the five essential parts of the laboratory report about this second experiment. Use your notes when orally describing the experiment. Look through the sentences below and try to complete them. In his second experiment, the soup in both flasks was.. for an hour. After the soup in flask A was, it as.. to stand for three days, open to the air. During these three days, the air entering flask B, however, was through a tube. Thus, the soup in flask B was boiled for an hour to. any microorganisms that might be present in the soup itself. Task 4 Listen to the text again and check the sentences you have completed.

7 ADDITIONAL READING Read the following questions and try to find the answers in the text 1. What is beer made from? 2. What is fermentation? 3. What are basic ingredients used to brew beer? 4. What influences the quality, colour and flavour of beer? 5. What are the essential steps in the brewing process? BEER Introduction Beer is an alcoholic beverage made from cereal grains, usually barley, but also corn, rice, wheat and oats. Beer is made using a process called fermentation, in which microscopic fungi called yeast consume sugars in the grain, converting them to alcohol and carbon dioxide gas. This chemical process typically produces beer with an alcohol content of 2 to 6 percent. Over 70 styles of beer are available today. Each style derives its unique characteristics from its ingredients and subtle differences in its brewing process. Throughout history, wherever cereal grains were grown, humans made a beerlike beverage from them: they used wheat in Mesopotamia, barley in Egypt, millet in other parts of Africa, rice in Asia, and corn in the Americas. Today, beer making is a major industry worldwide. In 1995 in the United States, 880 breweries produced more than 200 million barrels of beer, and on average, each adult American consumed nearly 121 litres (32 gallons) of beer. Beer Ingredients Four basic ingredients are used to brew beer: grain, hops, yeast and water. Grain contains the natural sugars required for fermentation. It also provides beer with flavour, colour, body, and texture. Hops provide beer with a spicy, bitter flavour and contribute natural substances that prevent bacteria from spoiling beer. Two species of yeast used to make beer, called brewer's yeast, are Saccharomyces cerevisiae and Saccharomyces uvarum. Each yeast species is used in a slightly different method of fermentation and produces a distinct type of beer. Water constitutes as much as 95 percent of the ingredients used in the brewing process. The mineral content in water-in particular, the levels of salts such as calcium, sulphate and chloride dissolved in the water influences the quality and flavour of the beer. Modern brewers add minerals and other natural elements to water or eliminate them by boiling or filtration so that the water used in the brewing process always produces beer with the same flavours. This enables brewers to produce identically tasting beer at different screwing locations throughout the world.

8 The brewing process The first step in brewing, called malting, involves steeping 1 the grain in water for several days until it begins to germinate (or sprout). During germination, enzymes within the grain convert the hard, starchy interior of the grain to a type of sugar called maltose. At this point, the grain is called malt. After several days, when the majority of the starch has been converted to sugar, the malt is heated and dried. This process, called kilning, stops the malt from germinating any further. A portion of the malt may be roasted to varying depths of colour and flavour to create different styles of beer. After kilning, the dried malt is processed in a mill, which cracks the husks /the outer coating of the grain/. The cracked malt is transferred to a container called a mash tun, and hot water is added. The malt steeps in the liquid, usually for one to two hours. This process, called mashing, breaks down the complex sugars in the grain and releases them in the water, producing a sweet liquid called wort. The temperature and amount of time used to mash the malt affects the body and flavour of the finished beer. ln the next step, called brewing, the wort is transferred to a large brew kettle and boiled for up to two hours. Boiling effectively sterilizes the wort to kill any bacteria that may spoil the wort during fermentation. During this stage of the brewing process, hops are added to the wort to provide a spicy flavour and bitterness that balances the sweetness of the wort. After brewing, the wort is cooled and then strained to remove the hop leaves and other residue. The brewer transfers the wort to a container in which it can ferment. This vessel may be a deep, flat container with an open top or a tall cylindrical vat with a conical base. Yeast is then added or pitched into the wort to begin fermentation. The first fermentation lasts from a few days to two weeks. When the yeast has consumed most of the fermentable sugar, the wort becomes beer. The beer is transferred to an air-tight container, called a conditioning tank, for a second fermentation or aging period, where the beer becomes naturally carbonated. Some brewers inject carbon dioxide gas into the beer when aging is complete to give it a bubbly, effervescent quality. Aging lasts for a few weeks to several months, depending on the type of beer being produced. 1 To soak in liquid in order to cleanse, soften, or extract a given property from it

9 VOCABULARY afflict anthrax arise available barley barrel contagious cornerstone devise disprove distinct postihnúť antrax, slezinná sneť vzniknúť dostupný, k dispozícii jačmeň sud nákazlivý základný kameň vymyslieť vyvrátiť zreteľný, odlišný gallon galón (Br. 4, 546 l Am.3, 785 l) germ germinate grain hop husk inhibit inoculate kilning malt malting mash tun millet mikrób, zárodok klíčiť obilie, zrno chmeľ šupka zabrániť očkovať sušenie slad sladovanie veľký sud proso

10 noted for oats prophylaxis rabies residue sprout starchy steep strain texture vat vessel virulent wort yeast známy niečím ovos prevencia besnota zvyšok klíčiť škrobnatý močiť, namáčať filtrovať, cediť štruktúra sud, kaďa nádoba prudko nákazlivý mladina kvasnice