Biology presentation


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Here´s a useful and complete presentation about a chapter of the book "el cocinero científico" of Diego Golombek. We hope you enjoy it.

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Biology presentation

  1. 1. Biology practical work: “El cocinero científico”Group members: Ignacio Duran, Victoria Gonzalez, Juan Germano, María Jachno, Clara Halvorsen, Sebastian Salinas, Andrea Gambarte, Juan Hevia.
  2. 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. 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. 4. Types of meatIn vertebrates, there are three types of meat:Smooth muscle (located around organs and blood vessels)Cardiac muscle (consisting on the meat related to the heart) Skeletal muscle (The muscles responsible of locomotion)
  5. 5. Which is the reason for meat´s 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. 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, which´s color is adark brown.
  7. 7. This process speeds up for other factors aswell: Due to microbes Extreme temperatures (including when its cooked) And a big concentration of salts This process is imposible to revert, and the older the meat, the darker the brown Brown meat Good quality meat
  8. 8. Animal From To The more oxygen Pig 40 150the musclerequires, the more Cow 280 500myoglobin ithas, and it has a Lamb 250darker red color. Horse 800 Whale 910 Concentation of myoglobin per 100 g of fresh muscle.
  9. 9. Cow meat In Europe and America, the most widespread bovine species is the Bos taurus. Brangus Hereford Red angusHowever, there are other bovine species, like the Bosindicus Which includes the cebu
  10. 10. Meat´s composition Water Proteins Fats, carbohydrat es and minerals Muscles contain groups of The fibers are located This connective tissue is composed microscopic fibers formed in semitransparent by a minor quantity by proteins (miosine and tubes of connective of 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. 11. Cow cuts Generally, an animal uses some muscles more than others. Among the muscles with greater development of connective tissue we found the muscles 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 are the 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. 12. Connective tissue collagen 2 components (proteins) elastinCollagen When sorrounded by heat and moist (the conditions of boiling water for example), it transforms in a jelly-like substance, making the meat softer. Elastin In contrast with collagen, it doesn´t softens in the presence of heat and moist However, heat and a longer Nonetheless, the effect of process of cooking results softening overwhelms the in a strenghtening of the negative effects on the fiber muscular tissues
  13. 13. With a quieter animal, better quality of meat… • Any stress before the moment of the death produces negative effects on the animal Unwanted When the muscles are music… active, they consume energy In 1979, a (glycogen) and produce lactic slaughterhouse in acid. Finland forced a group of musicians to leave the area because their When the animal dies, the music disturbed muscles keep working for some their cows and time, while the blood flow stops affected the and causes an accumulation of quality of their lactic acid meats. In consequence, the meat results gum-like and runs off faster, as acid concentration drops allowing bacteria and fungi to grow.
  14. 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 skin Myoglobin as a reservoir of oxygen, which is needed toburn fat to obtain energy for muscular activity reddish 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 Molecule Easily dissolved due to water and thus smell do not reach our noses. This is why people put water and lemon on their fingers before eating fish.
  15. 15. Flesh on Flesh• Effect over cooking meat: the proteins are denatured by heat and 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 consequences the passage of light is prevented, that´s why it looks opaque, and juice begins to appear, due to the water which was between the fibers.
  16. 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. 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. 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. 19. Storage of meattors that affect the edibility of the meat:Action of light and O2Enzymes and microorganisms present in the meat It depends on the type of meat:  Mammals and birds: Enzymes ns which accelerate the work at relatively high and cal reactions of and constant temperatures youism. The low temperatures of must put the meat in the fridgenzymes are good because they to slow the activity down he food not degrade  Fishes: Their temperature is similar to the enviroment. So the cooling can not stop their activity.n problems nowadays with the storage of meat are: FUNGI AND BACTERIAS. of fungi and bacteria which can affect the meat:
  20. 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, that´s why is convenient to freeze the meat very fast.
  21. 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 over food.
  22. 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. 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 it´s 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. 24. Jerky Curing: food preservation Linked to Latin American independence Dry meat jerky (or charqui in Spanish) Cut in slices Quechua Jerky Salted to preserve it origin: ch´arqui Can be crashed by a mortar From english verb “to jerk”Indigenouspeoples fromthe South With ñandu and Charqui, also guanaco meat called cecina
  25. 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 charqui”English translation: “having an eye on the jerky”. This is a commonexpression which means to pay attention and take care of a lovedpossession, something you don’t want to lose. • Mixture of smells Jerky • Smelled before being eaten • Gives a strong taste to potatoes
  26. 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 charquicán(an seasoned version of charqui), were prepared.
  27. 27. A pasta composed by dry meat flavouredCharquicán with fat and hot pepper. This together with corn flour meant an economic and nutritive meal. Cattle went together whit the troops for feeding and more cattle would be sent as soon as they reached Chile. Food wasn’t only meat. They had other supplies too such as biscuits, toasted corn flour and water. Jerky Not only nutritive, hygienic and highly concentrated. It also meant less weight to carry, as it was dehydrated meat. Meat is 70% water and a litre of water meant 1 kilogram. Therefore, meat severely reduced its weight.
  28. 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 it has less starch and the resulting noodles are a bit more fragile than if they are done with wheat flour. Part of the water can be replaced by fresh eggs, which gives them more color and taste. Pasta is sold dry, with 10% of water. Pasta sold in the supermarket is often dried-up over a day in the fabric. When pasta dries up, you have to be careful: moving it too much may lead to a break up of pasta but leaving it untouched gives bacteria the chance to start acting over the dough.
  29. 29. Cooking Pasta The starch of the dough releases a starch when it is cooked, which is gelatinized when it cools. If oil is added to water, it floats and is not in touch with the pasta but keeps the water from escaping. Once the pasta is done, oil or butter used cover the gluten and starch of the surface and avoid the pasta from being “sticky”. By cooking pasta with a lot of water, pasta swells and starch solution will be more diluted and that is why noodles will be less sticky. It is important to add salt to the water while cooking it because it will give it a better taste than if added before straining the pasta.
  30. 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. 31. Wild rice Basmati riceChinese rice