Meat and fish

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Year 13 Edexcel meat and fish structure and composistion

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Meat and fish

  1. 1. 1 Meat and fish a) Characteristics, structural composition and factors affecting: the component proteins (actin, myosin and actomyosin) to form muscle muscle contraction conversion of muscle to form meat fish quality b) The characteristic spoilage in: putrefaction of meat breakdown of fish tissues after catching development of odours c) The processes involved in: storage and handling of meat meat preservation canning freezing fish preservation chilling freezing d) Nutritional contribution to the diet.
  2. 2. Types of meat <ul><li>Cattle – beef </li></ul><ul><li>Pigs – pork </li></ul><ul><li>Sheep – lamb </li></ul>
  3. 3. Structure of meat <ul><li>Lean meat is the muscle tissues of animals. </li></ul><ul><li>Made up of: </li></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Protein </li></ul></ul><ul><ul><li>Minerals </li></ul></ul><ul><ul><li>Vitamins </li></ul></ul><ul><ul><li>Myoglobin </li></ul></ul><ul><ul><li>Lipids and sterols </li></ul></ul>
  4. 4. Structure of meat <ul><li>Meat muscle is made up of bundles of muscle fibres held together by creamy-white connective tissue . </li></ul><ul><li>Tendons join the muscle (made up of bundles of muscle fibres, surrounded by connective tissue) to the bones of animals. </li></ul>
  5. 5. Structure of meat <ul><li>Connective tissue is made up collagen and elastin, both fibrous proteins. </li></ul><ul><li>When meat is cooked, collagen becomes soft and soluble and forms gelatine which make it soluble and easier to digest. </li></ul><ul><li>Elastin is very elastic. Its yellow in colour. Remains tough when cooked. </li></ul><ul><li>Ligaments (which join bones together) are mostly made up of elastin. </li></ul>
  6. 6. Structure of meat <ul><li>Muscle fibres are made up of cells which contain proteins called actin and myosin . </li></ul><ul><li>Actin and myosin work together to make muscles contract and relax. </li></ul>
  7. 7. Structure of meat <ul><li>Short and fine muscle fibres come from young animals – they can be made tender quickly during cooking. </li></ul><ul><li>Long and thick muscle fibres come from older animals – muscle which do lots of work (neck and shin). Tougher meat. Needs long, slow cooking to make it tender. </li></ul>
  8. 8. Structure of meat <ul><li>When an animal is slaughtered the supply of ATP (produced during respiration, provide the store of energy that muscles use) runs out, causing the actin and myosin to gradually lock together (actomyosin). The actomyosin molecules formed are inflexible, making the muscle rigid and producing rigor mortis . </li></ul><ul><li>ATP=adenosine triphoshate </li></ul>
  9. 9. Colour of meat. <ul><li>Due to red protein called myoglobin and some haemoglobin (blood) left in the muscle. </li></ul><ul><li>Vary due to age and exercise </li></ul>
  10. 10. Cooking to improve tenderness <ul><li>Depends on structure of the muscle, age of the animal, the area of the animal it has come from. </li></ul><ul><li>During cooking muscle fibres coagulate (shrink and harden). As this happens, water is squeezed out of the meat and it shrinks in size. </li></ul><ul><li>Methods of tenderising? </li></ul>
  11. 11. Storage <ul><li>0-5oC to stop bacteria from spreading and avoid food poisoning. </li></ul><ul><li>Store raw meat in clean sealed containers on the bottom shelf of the fridge, so it can't touch or drip onto other food. </li></ul><ul><li>Don't eat meat after its 'use by' date. </li></ul><ul><li>When you have cooked meat and you're not going to eat it straight away, cool it as quickly as possible and then put it in the fridge or freezer. Remember to keep cooked meat separate from raw meat. </li></ul>
  12. 12. Storage 0-5oC
  13. 13. Preservation methods of meat <ul><li>The speed with which meat spoils not only depends on hygiene conditions and storage temperature, but also on the acidity of the meat and the structure of the muscular tissue. </li></ul><ul><li>The firm muscular tissue of beef, for example, spoils less quickly than liver. Hygienic slaughtering and clean handling of the carcass have a positive effect on storage life. </li></ul>
  14. 14. How canning food prevents food poisoning http://www.bbc.co.uk/scotland/learning/learningzone/clips/9213.flv
  15. 15. Nutrition of red meat <ul><li>Iron - is required for the formation of red blood cells. The iron contained in lean beef and lamb is in the form that is more easily absorbed by the body. </li></ul><ul><li>B vitamins - (thiamin, riboflavin, niacin, B6 and B12) - These vitamins are required for the release of energy and other metabolic functions in the body. Vitamin B12 is found only in foods of animal origin like lean beef and lamb, fish, milk, and eggs. B12 is required for the formation of red blood cells. </li></ul>
  16. 16. Nutrition of red meat <ul><li>Zinc - Red meat contributes about a quarter of zinc in the diet. It assists with the body's immune system to fight infection and diseases. Lean beef and lamb are important sources of easily absorbed zinc. </li></ul><ul><li>Fresh red meat is naturally low in salt. </li></ul>
  17. 17. Nutrition of red meat <ul><li>Protein - is required for growth and repair of body tissues. Lean meat provides about a quarter of the protein in the diet and is especially important for growing children and teenagers, those who are ill and those with a very active lifestyle. Proteins are made up of building blocks called amino acids. Lean beef and lamb contain all the essential amino acids required for growth and repair. </li></ul>
  18. 18. Nutrition of red meat <ul><li>Vitamin D - assists with the absorption of calcium. Research shows that lean red meat is a valuable source of vitamin D and the vitamin D in red meat is in a highly absorbable form. </li></ul><ul><li>Omega-3 fatty acids - Long chain omega-3 fatty acids have potential benefits in relation to heart health, especially those who have already suffered a heart attack. Only a small amount of these long-chain omega-3 fatty acids are found in meat. </li></ul>
  19. 19. Red meat and fat <ul><li>Excess dietary fat is one of several risk factors associated with coronary heart disease. </li></ul><ul><li>The greater proportion of the fat in lean beef and lamb is in the monounsaturated form, which is the type associated with a healthy Mediterranean type of diet. In lean lamb over a third of the fat is in the monounsaturated form. </li></ul><ul><li>The leanest form of beef and lamb today contains less than 5% fat, compared to at least 25% for beef and 31% for lamb in the 1970s. </li></ul>
  20. 20. Status of the world’s fish stocks <ul><li>Overfishing is widely acknowledged as the greatest single threat to marine wildlife and habitats. </li></ul><ul><li>Over-fishing means UK trawlers have to work 17 times as hard for the same fish catch as 120 years ago, a study shows. </li></ul>
  21. 21. Fish quality <ul><li>Fish pass into rigor and start to undergo bacterial deterioration immediately afterwards. </li></ul><ul><li>Put on ice or frozen to prevent bacterial growth as soon as caught. </li></ul><ul><li>Ammonia is often produced by bacteria when they attack the protein of fish muscle, aids to bad smell. </li></ul>
  22. 22. How fresh is my fish? <ul><li>Instrument uses light at different wavelengths to see how fresh the fish is. The fish flesh will absorb light at different wavelengths according to how it is stored and how long it has been since it was caught. </li></ul>The spectrometer is placed above the fillet. The colour spectrum is measured and storage time is calculated on the basis of these measurements.
  23. 23. Nutrition of fish <ul><li>Fish and seafood are high in protein. </li></ul><ul><li>White fish, such as cod, halibut and plaice, contain less than 5% fat. </li></ul><ul><li>Oil-rich fish, such as salmon, mackerel and sardines, is a valuable source of vitamin D and polyunsaturated fats called omega-3 fatty acids. These help reduce your risk of heart disease, and are thought to be important for the development of the brain of the unborn child, and for children. They may also help to ease inflammatory conditions, such as arthritis </li></ul>
  24. 24. Spoilage of fish <ul><li>Raw fish rapidly go off, even though they are stored in ice. </li></ul><ul><li>There are no carbohydrates in the flesh. So bacteria from the gut and gills start work on the proteins straightaway. </li></ul><ul><li>They produce the mix of chemicals that gives bad fish its unique smell. </li></ul>
  25. 25. Preservation methods of fish <ul><li>Fresh fish will spoil very quickly. Once the fish has been caught, spoilage progresses rapidly. In the high ambient temperatures, fish will spoil within 12 hours. Using good fishing techniques and cooling the fish, with the help on ice on board, can increase the storage life of fresh fish. </li></ul>
  26. 26. Preservation methods of fish <ul><li>Chilling </li></ul><ul><li>Freezing </li></ul><ul><li>Salting </li></ul><ul><li>Marinades </li></ul><ul><li>Drying </li></ul><ul><li>Smoking </li></ul><ul><li>Canning </li></ul><ul><li>Using Proudlove, page 119-121 write about these preservation methods. </li></ul>

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