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Nutrients: Protein

Nutrients: Protein. Protein: What is it?. One of the six nutrient groups Composed of carbon, hydrogen, oxygen and nitrogen During digestion, they are released to their simplest form - Amino Acids Amino Acids There are approximately 22 needed by the human body

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Nutrients: Protein

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  1. Nutrients: Protein

  2. Protein: What is it? • One of the six nutrient groups • Composed of carbon, hydrogen, oxygen and nitrogen • During digestion, they are released to their simplest form - Amino Acids Amino Acids • There are approximately 22 needed by the human body • 13 are made by the body – Non Essential Amino Acids • 9 are not – ESSENTIAL Amino Acids – must be supplied by the diet (8 for adults)

  3. Protein: Why do we need it? Proteins are found in all body cells and are essential because they: • Allow the body to grow and repair • Form the basis of many of the body’s chemical substances: antibodies, hormones, enzymes and haemoglobin • Can provide energy (17 kilojoules per gram) when there is insufficient carbohydrates or lipids (fats) • It regulates body processes, such as water balancing, transporting nutrients, and making muscles contract.

  4. Protein: Where can I get it? Protein is found in a variety of foods but the quality will differ. Complete Proteins – food sources that have a High Biological Value (HBV) because they provide the body with all of the Essential Amino Acids – generally from animal sources (& soy beans) Incomplete Proteins – food sources that have a Low Biological Value (LBV) because they provide the body with most but not all Essential Amino Acids – generally from plant or vegetarian sources Supplementary/Complementary Values of Protein – the combination of incomplete proteins in order to supply the body with all of the Essential Amino Acids – especially useful for vegetarians

  5. Protein: How much do I need? • The Recommended Daily Allowance is .8 grams of protein for every 1 kilogram body weight So: (body weight) x 0.8 = _______g/day Example: Brandon weighs 47kg. How many grams of protein should he aim for each day? 47 x 0.8 = 37.6g protein each day

  6. Protein: How do I get enough? Again, this is where the Food Composition Tables will come in very handy:

  7. Protein: Too much or not enough?

  8. Cooking with Proteins

  9. Protein: Properties Different cooking processes cause different changes in proteins These changes are generally permanent (cannot be reversed) and are called Denaturation This Denaturation occurs in 2 ways: - tenderization of meat and poultry - coagulation

  10. Protein: Tenderisation • The process of breaking down the collagen in meat to make it easier to consume.

  11. Protein: Coagulation • to form into a soft mass: to curdle, clot or congeal • occurs when a liquid protein changes to a solid • can occur as a result of a number of processes used in food preparation: - Heat - Acids - enzymes - agitation

  12. Protein: Coagulation Examples • When an egg is fried, the white and the yolk both set firm and change colour. • When an egg white is beaten, the foam becomes stiff and firm because the protein in the white coagulates. If it is heated it, as in making meringue or pavlova, it coagulates even further. • When milk has lemon juice added to it, the acid cause the protein to clot. We say that the milk has curdled. The same thing happens when milk goes sour. • When a junket tablet is added to warm milk, the enzyme rennin in the tablet causes the milk to set. When the junket is broken, the clot separates into curds and whey. • When meat is heated, it changes from red to brown and the limp muscle becomes stiff. Continued heating causes the protein to contract, and the meat shrinks. High temperature causes the protein to become tough and indigestible, as the protein over coagulates. • A skin forms on milk when it is heated. Steam collects under the skin, and when the pressure is great enough, it breaks the skin, and milk rises in a rush to boil over.

  13. Protein: Cooking • Moist and dry heat coagulates protein at approximately 75C and improve its appearance. • Moist heat softens the protein, some of which will dissolve into the gravy • Overcooking or cooking at too high a heat makes protein tough, hard, dry and indigestible, for example - cheese goes stringy - eggs curdle or go tough and leathery -meat becomes tough and hard • for best retention of nutritive value, meat should be sealed first at high temperature to reduce loss of moisture, then the heat reduced to low or moderate

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