Presentation on theme: "PROTEINS. What are proteins? Proteins are complex molecules that make up as much as 50% of the dry weight of living cells. These molecules are composed."— Presentation transcript:
What are proteins? Proteins are complex molecules that make up as much as 50% of the dry weight of living cells. These molecules are composed of carbon, hydrogen and oxygen. In addition, proteins contain nitrogen and usually sulfur. Some proteins also contain iron, copper, phosphorus or zinc.
Why do we need protein? Support Growth and Repair Fight Disease Maintain Fluid and Mineral Balance Maintain pH Balance Control Bodily Functions Provide Energy
Primary sources of protein Eggs Diary Products Meat Poultry Fish
Structure of Protein Protein molecules are made up of subunits called amino acids. There are 20 amino acids in the human body. Proteins are chains of many amino acids bonded together.
Structure of Protein When two amino acids combine, a water molecule is released. The bond between them is called a peptide bond. A dipeptide is a protein molecule made up of two amino acids. A polypeptide is made up of many protein molecules.
Structure of Protein
Structure of Protein 20 amino acids used in the body are necessary for growth and body functions. 8 of them are essential amino acids meaning they cannot be produced by the body. The essential amino acids must be supplied by foods in the diet. There is a ninth amino acid called histamine that is essential for infants.
Structure of Protein Foods that contain all 8 essential amino acids are called complete proteins. Most complete proteins come from animal sources. Foods that do not contain all 8 essential amino acids are called incomplete proteins. Incomplete proteins also known as limiting amino acids come from plants.
Plant sources Many people around the world get their source of protein from cooked dry beans, nuts and seeds. Combining legumes with grains, nuts or seeds will generally create a complete source of protein. Eating less animal-based protein reduces the amount of saturated oils and cholesterol you ingest.
Plant Source Combinations Whole wheat bread and peanut butter Rice and red beans Refried beans and corn tortillas Hummus – a dip made with chickpeas and sesame seeds
How much Protein do we need? A 154lb man needs to consume 56g of protein daily. A 120lb woman should consume 44g of protein daily. How many grams of protein should you consume in a day?
AMERICAN DIET On average, men consume 90g/day and the women consume 70g. Our intake his high because we eat meat with every meal. A single serving of meat is considered to be 3 oz. Few of us have this portion. The daily requirement is 5-7 oz. In one meal we can get all of the protein needed in one setting. 1 ounce = 28 grams
DENATURATION OF PROTEIN The loosening or unfolding of the protein molecule. Is usually not reversible. Methods of denaturation include: Temperature Change Mechanical Action Chemical Action
FUNCTIONS IN FOOD Form Gels Texturize Emulsify Form Foams Develop Gluten
EGG stra Information Eggs lose CO 2 through the eggshell and the pH changes from neutral to basic. The change in pH causes the proteins to break apart. Over time the water in an egg moves into the yolk. This action stretches and weakens the yolk membrane. So, fresh is better for separating and for frying.
EGG stra Information High Heat + Long Time = Firm Egg White Low Heat + Short Time = Soft Egg White
EGG stra Information Hens lay fewer eggs during the winter months. When eggs are plentiful they are dipped in mineral oil and put in cold storage. Eggs are more expensive between Christmas and Easter.
MOO NEWS Two common problems can occur when cooking milk. Curdling – when protein molecules in milk unfold and stick together. Scorching – when protein clumps formed by heat sink and then burn on the bottom of the pan.
COOKING MEAT MOST MEATS CONTAIN 3 CATAGORIES OF PROTEINS: Muscle Fibers Connective Tissue Myoglobin One of goals in cooking meat is to soften the connective tissue
COOKING MEAT The most important goal in cooking meat is to reach the recommended internal temperature for the meat you are cooking. Checking meat with a food thermometer will ensure that meat and poultry are cooked to the desired degree of doneness. Improper cooking can result in bacterial contamination
HEATLH NEWS IT IS VERY IMPORTANT THAT POULTRY AND PORK ARE COOKED TO RECOMMENDED TEMPERATURE. HOW WOULD YOU KNOW IF YOU DID NOT COOK IT? IF IT IS NOT SMOKED, IT SHOULD NOT BE PINK. IF THE MEAT JUICE IS PINK, IT IS NOT DONE. HOWEVER DARK RED STAINS NEAR BONES IN POULTRY DO NOT RELATE TO DONENESS.
MYOGLOBIN An iron-containing protein that holds oxygen in muscle tissue. Gives meat its bright red color. Not to be confused with hemoglobin that is found in the blood. The red juice from raw meat products is not blood, it is water with dissolved myoglobin.
MORE ON MYOGLOBIN PORK IS LIGHTER THAN BEEF BECAUSE IT CONTAINS LESS MYOGLOBIN. POULTRY BREASTS AND WINGS ARE LIGHTER THAN LEGS AND THIGHS BECAUSE OF MYOGLOBIN. BREAST AND WINGS ARE DESIGNED FOR SUDDEN USE AND BURN GLYCOGEN, WHICH DOESN’T REQUIRE OXYGEN, FOR ENERGY.