1. Biology practical work:El cocinero cientficoGroup members: Ignacio Duran, Victoria Gonzalez, Juan Germano, Mara Jachno, Clara Halvorsen, Sebastian Salinas, Andrea Gambarte, Juan Hevia.

2. We are of meat The meats have a special place in the Occidental World diet, especially inArgentina.Interest in meat attracted the attention of specialists from differentaffiliations. Meat comes from the latin "caro". The meat itself is the muscular tissue of animals, whose function is to movethe animal from one place to another. With the arrival of the Homo erectus an omnivorous diet that includesfruits, roots and meat was introduced.What is the advantage of eating meat?Animal tissue generally have a proportion number ofamino acids similar to those of humans. Oneadvantage of the meat is that it provides B12 vitaminand that has a high protein content. 3. In general, everytime we say meat, we mean every eatable part ofthe animal. But meat really means the muscular tissues, which allowthe animal to move from one place to another.Why do we eat meat? What is the advantage of eatingmeat? One possible explanation is that we eat meat because animals aresimilar to us and so their chemical compounds. Animal tissues, incontrast with plants, have a similar proportion and number ofaminoacids. This is why vegetarians ought to be more careful abouttheir diet. The other advantage is the high level of proteins meat has. 4. Types of meatIn vertebrates, there are three types of meat:Smooth muscle (located around organs andblood vessels)Cardiac muscle (consisting on the meatrelated to the heart) Skeletal muscle (The muscles responsibleof locomotion) 5. Which is the reason formeats color?Mainly, its caused by myoglobin, proteins which contain groups of atoms called heme (containing iron), used to store oxygen or to use it.Both the concentrarion (Which varies from one animal to the other)and the state of the molecule afects the color. 6. When myoglobin stores oxygen, its color isred. After the animal is dead, its reverts to itsdeoxygenated form and turns purpleOnce the meat is cut, it is exposed to oxygenagain, obtaining once again the red color.Now, due to the fact that oxygen difuses withdificulties through meat, if the meat is exposedto a low oxygen concentration the myoglobinturns into metmyoglobin, whichs color is adark brown. 7. This process speeds up for other factors aswell: Due to microbes Extreme temperatures (including when its cooked) And a big concentration of saltsThis process is imposible to revert, and theolder the meat, the darker the brown Brown meat Good quality meat 8. Animal FromToThe more oxygenPig 40 150the musclerequires, the more Cow 280500myoglobin ithas, and it has aLamb250darker red color. Horse 800 Whale 910 Concentation of myoglobin per 100 g of fresh muscle. 9. Cow meat In Europe and America, the most widespreadbovine species is the Bos taurus.Brangus HerefordRed angusHowever, there are other bovine species, like the BosindicusWhich includes the cebu 10. Meats composition Water Proteins Fats, carbohydrat es and mineralsMuscles contain groups ofThe fibers are located This connectivetissue is composedmicroscopic fibers formed in semitransparentby a minor quantityby proteins (miosine andtubes of connectiveof cells and much actine) tissue extracellular tissue Connective tissue is responsible for the toughness of the meat. Therefore, with moremovement of the animal, greater development of connective tissue, which results in a toughermeat Thus, bovines raised in open fields will have tougher meat, as the connective tissue is more developed For example, japanese breeders give their cows massages to relax the muscles and prevent them from exercising 11. Cow cutsGenerally, an animal uses some muscles more thanothers. Among the muscles with greaterdevelopment of connective tissue we found themuscles of the limbs, the tail and the neck.Thus, these parts are the toughest cuts of a bovine.In contrast, the muscles that suffer less exercise arethe softer ones. Another matter about meat toughness is the age of the cow, asolder animals will be able to move more. Moreover, growth alsocauses the connective tissue to become stronger, contributing to the toughness of the meat. 12. Connective tissue collagen2 components(proteins)elastinCollagenWhen sorrounded by heat and moist (the conditions ofboiling water for example), it transforms in a jelly-likesubstance, making the meat softer.ElastinIn contrast with collagen, it doesnt softens in the presence of heat and moistHowever, heat and a longerNonetheless, the effect of process of cooking results softening overwhelms the in a strenghtening of the negative effects on the fibermuscular tissues 13. With a quieter animal, better quality of meat Any stress before the moment of the death produces negative effects on the animalUnwanted When the muscles are music active, they consume energyIn 1979, a (glycogen) and produce lacticslaughterhouse inacid. Finland forced agroup of musiciansto leave the areabecause theirWhen the animal dies, the music disturbed muscles keep working for sometheir cows and time, while the blood flow stops affected theand causes an accumulation of quality of theirlactic acid meats.In consequence, the meat resultsgum-like and runs off faster, as acid concentration dropsallowing bacteria and fungi togrow. 14. Fish Meat Muscles: short fiber segments separated by transverse connective tissue layers. Only 3 per cent of the animals weight Meat: white color Slow muscle fibers form a thin layer which is located on theperiphery of the animal under the skinMyoglobin as a reservoir of oxygen, which is needed toburn fat to obtain energy for muscular activityreddish layer. Furthermore, the cells of fast fibersused mainly carbohydrates: do not require Oxygen and have little myoglobin, so color is white. Molecules called amines: formed by the nitrogen group (amino-group). They are very smalland highly volatile. This is the reason we smell them easily.In the presence of acid, the next reaction takes place:R-NH2+H+ R-NH3+ Positive Charge amine protonCharged MoleculeEasily dissolved due to water and thus smell do not reach our noses. This is why peopleput water and lemon on their fingers before eating fish. 15. Flesh on Flesh Effect over cooking meat: the proteins are denatured by heatand are easily attacked by enzymes of the digestive system.First, the proteins of meat loose the shape due to heat. They begin to formsolid masses with consequencesthepassageoflight isprevented, thats why it looksopaque, and juice begins toappear, due to the water whichwas between the fibers. 16. Heat produces the typical flavor of cooked meat, in two ways.By damaging the cells, the heat makes allthe compounds, the intra and extracellular,get into contact, which promotes reactions betweenamino acids, sugars, minerals, fats and enzymes.The intense heat favors reactions called pardas (brown color), where the sugars and amino acidsof the meat can be linked with each other and create many types of compounds, some of themtasty, others with toasted color and smell. 17. Its the way it feels to the touch; how easily it can be shredded by a knife or by the teeth.As seen before, it can be changed. For example, it can be made softer by heating, cutting, hitting it and other ways. 18. Tenderizers Another way of softening the meat is with atenderizer, which unwinds and cuts proteins. Tenderizers can also be found in nature, in the formof bromelain in pineapples and in pawpaw in the formof papain ,to give some examples. 19. Storage of meattors that affect the edibility of the meat:Action of light and O2Enzymes and microorganisms present in the meatIt depends on the type of meat: Mammals and birds: Enzymes ns which accelerate thework at relatively high and cal reactions of and constant temperatures youism. The low temperatures ofmust put the meat in the fridgenzymes are good because theyto slow the activity down he food not degrade Fishes: Their temperature issimilar to the enviroment. Sothe cooling can not stop theiractivity.n problems nowadays with the storage of meat are: FUNGI AND BACTERIAS. of fungi and bacteria which can affect the meat: 20. Cold StorageRefrigeration is the most popular method to preserve meat.The aim of this method is to reduce the working of bacteria and enzymes. What happen during freezing?The more salts the water has the lower the temperature at which it freezes.Another important fact is that the concentration of salts within the cell is higherthan outside the cell. Finally, the ice is less dense than water, that is when liquidwater is transformed into ice, it occupies more volume.When to thaw again raise the temperature, the meat loses much fluid andbecomes drier, and therefore harder than it shouldAs the temperature of the meat reaches the freezing point, some ice crystalsbegin to form between the muscle cells. These crystals burst into the cellmembranes and cause them holes, thereby exposing achieved muscle proteinsexternal fluid.So, thats why is convenient to freeze the meat very fast. 21. WARMINGackaging first appeared when in 1810 Nicolas Appertiscovered that by sealing food while warming it, it wouldot rot. In pasteurization, food In sterilization, all is warmed while trying to organisms are destroyed cause the least harm to it. regardless of its effects overfood. 22. SMOKEDSmoked is a preservation technique that consists in a type of slow cookingand at low temperature.Smoke is formed by: Alcohols Acids Phenols Several ToxicsToxics Inhibit the growth of microbes, Phenols hold up the oxidation of fatsand this whole process gives meat that flavor characteristic of burnt wood.This proccess is often combined with curing to minimize the fatoxidation produced by it 23. Curing is a process which uses salt mixed with sugar and other species toobtain a type of meat that differs from other meat-based products becauseof its texture, smell, flavour, and because of a resistant- to- cooking colour.The salt takes out the water from inside the cells; but it also causes thedestruction of many proteins, which makes the the meat have more fat.Curing has an influence on the colour of the meat. Salty meats keep theirred-pink colour even after cooked. This is due to a chemical compoundpresent in the salt called nitrite. This reacts with the purple pigment to forma molecule of nitrosomyoglobin, which is pink. This compound is very stableto changes in temperature, but is sensible to oxygen and light. For thisreason, cured meat is usually vacuum packed and not exposed to light.Nitrite is a very efective antibacterial agent wich slows down oxidation andcontributes to the flavour of the meat. 24. JerkyCuring: food preservationLinked to Latin American independence Dry meat jerky (or charqui in Spanish) Cut in slices Quechua Jerky Salted to preserve it origin: charqui Can be crashed by a mortarFrom english verbto jerkIndigenouspeoples fromthe South With andu and Charqui, also guanaco meat called cecina 25. Meat preparation1) Cutting it into large thin slices(separating the fat). Sometimes the meatis partially frozen so as to cut it moreeasily.2) Salt is added and meat is dried slowly.Nowadays in stead of being dried by thesun, ovens are used. The optimumtemperature is 120 -130 C. A well driedmeat can be maintained in an hermeticbox for 1 or 2 months.Ojo al charquiEnglish translation: having an eye on the jerky. This is a commonexpression which means to pay attention and take care of a lovedpossession, something you dont want to lose. Mixture of smells Jerky Smelled before being eaten Gives a strong taste to potatoes 26. The jerky and the crossing of the AndesJose de San Martin, unknowingly, used a gastronomic strategy, very useful forrefrigeration in those days: curing. Part of the success in the crossing of the Andeswas thanks to jerky.Towards the end of 1815, months before the declaration of independence, San Martinannounced his intention for crossing the Andes to Chile and fighting the Spaniardsthere. 700 slaves between 16 and 30 years old were incorporated to the army (notthose who worked in agriculture or trade).To feed the troops, San Luis provided San Martin with cattle. Jerky and charquicn(an seasoned version of charqui), were prepared. 27. A pasta composed by dry meat flavouredCharquicnwith fat and hot pepper. This together withcorn flour meant an economic andnutritive meal.Cattle went together whit the troops for feeding and more cattlewould be sent as soon as they reached Chile.Food wasnt only meat. They had other supplies too such asbiscuits, toasted corn flour and water. JerkyNot only nutritive, hygienic and highlyconcentrated. It also meant less weight tocarry, as it was dehydrated meat. Meat is70% water and a litre of water meant 1kilogram. Therefore, meat severelyreduced its weight. 28. Spaghettis, Vermicellis and the Campanelli Pasta became popular in the 18th century. The base for pasta is water and wheat or semoline flour. If semoline flour is used, less water is required because ithas less starch and the resulting noodles are a bit morefragile than if they are done with wheat flour. Part of the water can be replaced by fresh eggs, whichgives them more color and taste. Pasta is sold dry, with 10% of water. Pasta sold in thesupermarket is often dried-up over a day in the fabric. When pasta dries up, you have to be careful: moving it toomuch may lead to a break up of pasta but leaving ituntouched gives bacteria the chance to start acting overthe dough. 29. Cooking Pasta The starch of the dough releases a starch when it iscooked, which is gelatinized when it cools. If oil is added to water, it floats and is not in touch with thepasta but keeps the water from escaping. Once the pasta is done, oil or butter used cover thegluten and starch of the surface and avoid the pasta frombeing sticky. By cooking pasta with a lot of water, pasta swells andstarch solution will be more diluted and that is whynoodles will be less sticky. It is important to add salt to the water while cooking itbecause it will give it a better taste than if added beforestraining the pasta. 30. A GRAIN OF RICE Since Alexander the Great brought the rice from Asia to Europe, has become the most famous foodworldwide. Nowadays, there are approximately 250,000 different varieties, in places where there is is goosoil and plenty of water. Rice grains undergo a long process before reaching the pan. The shell is removed and then therice is mechanically polished. Sometimes sugar is added to brighten it and almost always a vitaminsolution is added to fortify the grain. The Indian rice is precooked with vapor (preboil), thus the nutrients are set in the grain. Wild rice: it is one of the most expensive types of rice. It comes from North America and the excuse of its cost is that it is harvested by hand. However, since the middle 20th century it has lost much of its savagery, as it is cultivated and harvested in factories. Once harvested, it is fermented to give a particular taste and heated to gelatinize the starch thus giving it a brown colour. Brown rice: every rice comes wrapped in a shell, which, when it dries up, leaves a light brown rice, wrapped in layers of bran. Bran is then polished until the grain is completely white. Chinese rice: it is fairly polished, and has a high content of glycogen. Therefore, it absorbs a lot of water during cooking. When cooked, the rice becomes sticky due to the high quantity of water and glycogen that it contains. Basmati rice: known as the queen of fragrances,original of India and Pakistan, this rice is aged so that the water is lost and, as a result, the smell and flavor stronger. The secret of a good rice is in the amount of water that is added. However, this also depends on thetype of rice. 31. Wild riceBasmati riceChinese rice