NFS 53 1st Edition Lecture 18Outline of Last Lecture I. Milk and Cheesea. Components of Milkb. Lactosec. Milk Fatd. Ashe. Dairy Proteinsf. Casein, the king proteing. Soft Cheeseh. Semi-soft and hard cheesei. The effects of rennet on milkj. Manufacturing control pointsk. My researchl. CrystallizationII. Midterm reviewa. Conceptsb. Sample QuestionsOutline of Current Lecture I. Eggsa. Types of eggs consumedb. Egg structurec. Why chickens?d. Parts of the egge. Egg cookery If. Egg cookery IIg. Egg cookery IIIThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LectureI. Eggsa. Types of eggs consumedi. Chicken, turkey, duck, quail, turtle, crocodile, fishb. Egg structurei.c. Why chickens?i. Chickens are “indeterminate layers” and will keep producing eggs indefinitely as long as they are taken away.ii. Can develop a system for “egg production” that trumps the simple biology of reproducing the chicken species.iii. 8 billon chicken eggs consumed in the United States.d. Parts of the eggi. Chalazae1. The chalazae are twisted cords of egg white that anchor the yolk to the egg itself – this is why the yolk sits in the middle of the egg.2. The chalaze can be a challenge when cooking with eggs. 3. The air pocket always found in eggs is a product of two protective membranes pulling away from each other so that the growing chick (usually not present) can have air. 4. The air pocket is an indicator of freshness – larger is less fresh.ii. Egg Shell1. Of course, not particularly important for food2. Has been used for cooking in the past, particularly in mixes used to clarify various hot liquids (coffee, consommé) 3. Is permeable to gases, but is covered (initially) by an impermeableproteinaceous cuticle that breaks up as the egg ages4. Color is related to flavor only in that brown-egg breeds may be unable to metabolize cholineiii. Egg Yolks1. Contains 75% of the calories of the egg (in the form of lipids), as well as most vitamins and minerals (iron, thiamin, Vitamin A).2. Color comes from plant-derived xanthophylls, thus color determined by what the chicken eats. 3. Made up of tightly packed spheres, containing subspheres, containing subsubspheres.iv. Egg White (Albumen)1. Mostly water (90%) and protein. 2. The proteins in the egg white are important for the versatility of cooking with eggs, and determine egg structure both when raw and when cooked.v. Ovalbumin1. Ovalbumin is the majority of the protein in eggs. This protein gels easily and denatures easily when heated. It also contributes to theoverall flavor and texture of the eggs. 2. Before cooking an egg, the egg white is very clear and translucent. The proteins are held together loosely, which allows light to pass through. 3. As the egg white cooks however, it begins to turn opaque white. Why?4. The proteins have denatured and have coagulated resulting in a tighter protein network that blocks the light.vi. Ovomucin and Ovotransferrin1. Ovomucin is the compound that keeps egg white thick and determines the quality of the egg from a commercial and culinary point of view.2. Ovotransferrin is a defensive protein that makes iron non-bioavailable, but it also coagulates first and so determines the temperature at which eggs sete. Egg cookery Ii. Protein coagulation1. Similar to milk proteins2. Coagulation is when proteins that do not interact for whatever reason are made to do so, and form a solid mass where previouslythey had been disassociated3. In milk, this happens with casein either in the presence of acid or rennet (chymosin), or with lactoglobulin in the presence of heat and acid and the absence of casein it can bind to4. Want to “denature” or unfold the globular proteins by physically or chemically breaking the bonds that hold them in their original, compact, folded shape5. Want to concentrate the proteins enough allow them to interact and bond, forming a network which, on the macro scale, is a solid mass6. But in eggs the process is different than in milk – we almost alwayswant to avoid overcoagulation, which, for example, makes scrambled eggs lumpy or even gritty, with an unappealing surface moisture7. “It’s all about the heat, the heat”a. All of the parts of the egg coagulate below 212 ºF (boiling point of water at sea level) b. The different parts of eggs coagulate at different temperatures – yolks between 150 and 160, whites between 145 and 180 (it takes a long time for ovalbumin toset), and the mixture around 165.ii. Coagulation Control1. Acids and salts encourage earlier but less complete coagulation2. Acids lower the pH and thus neutralize the generally negatively-charged proteins in eggs3. Salts do something similar, with their disassociated ions again neutralizing the proteins4. Proteins are less unfolded in each case, and cannot unfold easily once coagulated – this produces a more tender final product. 5. Extra liquid, sugar, and fat delay coagulation and produce a more tender final product (as in milk or cream – common additions to eggs)f. Egg cookery IIi. Emulsification1. Egg yolks are particularly rich sources of emulsifiers, mostly low-density lipoproteins and phospholipids2. This is due to the complex aggregations of proteins, lipids, and membrane-forming compounds in egg yolks3. Egg yolks can emulsify an astonishing amount of oil and water – a single egg yolk can emulsify more than a dozen cups of oil, although extra non-oil liquid must be added to accommodate the full volume of that oil 4. Salt, which as we addressed previously disrupts yolk structure, makes egg yolk a far more effective emulsifier, as it makes more ofthe substructure available to use for emulsification.g. Egg cookery IIIi. Foams 1. The two parts of eggs stabilize foams differently2. Egg white foams are the most common and can be made just by whipping egg whitesa. The proteins in egg whites are unfolded by beating, exposing portions that are nonopolar, which are then attracted to the bubbles being introduced by beatingb. Once unfolded and concentrated at the surface of bubbles,the proteins bond to each other, forming a network that traps the bubbles and makes a stable foamc. Acids and copper help stabilize the foam by preventing over-bonding between proteins – they both cause sulfide bonds between cysteine groups to be unable to formd. Sugar makes foams more dense and stabilizes them by making the liquid