Exam 3 Food Science

Fried eggs

Egg quality and controlled heating are the keys to achieving a pleasing fried egg •Breaking the yolk while turning or removing it from the pan is more likely when the vitelline membrane is weak (older egg)

Egg foam dishes

Egg foams enhance egg dishes, including divinity candy, soufflés, frittatas, angel food cake, and other cake batters.

Healthier/ plant based alternatives

"Diet"/light butter and margarine- 50-80% fewer calories, much more water Promise Activ Light Spread (formerly Take Control) Benecol Smart Balance Earth Balance

Egg white

58% of egg weight • Protein is albumin (about 3.6g in a large egg -Ovaalbumin- 54% of the protein -Conalbumin- ability to bind to metals like iron, aluminum & copper causing undesirable color changes -Lysosyme- antibacterial action- prevents spoilage in eggs • Water 87-90% • No fat • B Vitamins -Riboflavin -Biotin

Cis & Trans

Dairy foods, meats have some natural trans configured FA's- probably not harmful in natural form Most common natural configuration is cis most trans fats are formed in commercial processing during hydrogenation

Chemistry of egg cooking

140°F - Egg white begins to thicken •150°F - Egg white becomes a tender solid; Yolk proteins begin to thicken •158°F - Yolk proteins set •165°F - The whole egg sets Milk, cream, and sugar dilute the egg and raise the temperature of thickening (coagulation) -Example: cooked custard (w/ milk, sugar, egg) starts to coagulate at 175-180°F Overcooked scrambled eggs may turn green due to formation of ferrous sulfide

Yolk

30% of egg weight 1/2 water • Fat - 6g in a large egg Triglycerides -Monounsaturated (47%) -Saturated (37%) -Polyunsaturated (16%) -Cholesterol - 186 mg per egg -Phospholipids -lecithin protein - about 2.7g in a large egg Vitamins & minerals: A, D, E, K, B-12, thiamin, iron

How to tell if eggs are bad

A "sell by" date indicates how long a store should offer eggs for sale -no more than 30 days after packing • An expiration date, marks the date after which the eggs are considered fresh. If your eggs are still within the expiration or "sell by" date on the carton, or within 21-30 days after the "pack date," you can be pretty sure they are still fresh. • Eggs that have been graded by the USDA are required to show the "pack date" on the carton, which is the day that the eggs were graded, washed and packaged. -The "pack date" is printed as a Julian date, meaning each day of the year is represented by a corresponding, chronological number. January 1st is written as 001 and December 31st as 365. • And even though the quality of an egg may start to decline after a certain date, it may still be good to eat for several weeks — especially if it has been refrigerated, which preserves quality and prevents bacterial growth. • Conduct a "Sniff Test"- Smelling the egg is the oldest, simplest and most reliable method of telling whether an egg has gone bad. -If you bought local eggs, they may not have a date. -Eggs that have gone bad will give off an unmistakable smell, regardless of whether they are raw or cooked. - If there is no odor at all, that's a good sign that the egg is still safe to use.

Hard cooked eggs

A large air space indicates that considerable carbon dioxide and water have been lost. • A well-centered yolk indicates a large amount of thick white • A darkish green ring of ferrous sulfide around the yolk is more likely to form in an older egg -Long heating promotes development of ferrous sulfide Firmness of the coagulated white is influenced by the final temperature reached in the egg -Also the temperature of the cooking water Hard-cooked eggs with whites at a pH of at least 8.8 (older eggs) are easier to peel than less basic eggs Hard-cooked eggs can be held in a brine or organic acid solution to help preserve them The solution used will modify flavor somewhat if the eggs are held more than a day

Egg Foams

A mass of bubbles, filled w/ air, and the egg white spread out into a thin film forming the bubble wall •Whipping unfolds protein molecules out of their usual shape and incorporates air bubbles •Proteins gather where air and water meet, and form new bonds •Forms a continuous solid network of proteins holding both water and air in place

Trans fat reduction

AHA Recommendations: limit consumption to <1% of total daily calories (2g on a 2,000-calorie diet) January 2006 labeling requirement - Manufacturers can declare 0g fat if the amount is <0.5g per serving Many large restaurants have switched to using trans-fat free frying oils 2006: NYC the 1st major city to pass regulation limiting trans-fat in restaurants Consumer education: read labels & watch saturated fat If package lists partially hydrogenated oil as ingredient it can contain 2 or more grams if 4 or 5 servings are consumed at one time Two-prong approach: reduction of trans-fat in food supply and decrease intake

Cages

About 90% of U.S. eggs come from hens living in large buildings with multilevel cages. • Most cage-free hens also live in large buildings with a similar controlled environment, but instead of cages, they live on the floor.

Acrylamide

Acrylamide is a natural carcinogen which forms in foods during a chemical reaction between asparagine, an amino acid, and sugars- part of the Maillard reaction occurs at elevated temperatures, 120 degree Celsius (248 degree Fahrenheit) used for frying, roasting and baking. Frying causes the highest acrylamide formation Occurs primarily in plant based foods, potato products like french fries and potato

To stabilize egg foam

Add -Acid - lemon juice, cream of tartar -Sugar -add near the end of beating Cooking makes denaturation permanent

Cages and egg types

Battery Cages: The humane treatment of hens comes into question with this housing system Cage-Free Eggs: A laying hen may live on the floor of a large building with controlled temperature and light but have no access to the outside or fresh air.. Free Range Eggs: Commonly describes the laying hens housing as providing access to the outside, or that the hens live on a small farm with free access to the outside. Organic Eggs: Hens must live in cage-free environments with access to the outdoors including direct sunlight. Hens must also be fed a 100% plant- based diet.

Egg Variations

Blood spots. -do not indicate a fertilized egg, are caused by the rupture of a blood vessel on the yolk surface during formation of the egg -Both chemically and nutritionally, eggs with blood spots are fit to eat. You can remove the spot with the tip of a knife, if you wish. A cloudy albumen shows freshness of an egg. Pink or iridescent egg white indicates spoilage. A green ring results from sulfur and iron -reaction between sulfur in the whites and iron in the yolks - harmless -occurs when eggs have been cooked for too long or at too high a temperature

Fatty Acids cont.

Building blocks for triglycerides A chain of carbon and hydrogen atoms with a carboxyl group (acid) at the alpha end and a methyl group at the omega end

Animal fats: butter

Butter must have a minimum of 80% butter fat, from pasteurized cream - 16% water; 4% protein, lactose Oil-in-water emulsion of cream becomes water-in-oil emulsion of butter 10 quarts of milk produce 1 lb of butter ~100 cals/Tablespoon 11g total fat/7g saturated Types- Sweet cream (salted or unsalted), whipped, clarified, ghee Salted: 45-120 mg sodium per tablespoon Carotene or annatto seed extract may be added for color Butter is commonly sold in quarter pound segments in half pound or 1 pound packages

Functional properties and applications

COAGULATION- WHEN PROTEINS START TO THICKEN -Eggs are used as thickening agents in many food products due to the effect of heat on their proteins. Coagulation indicates a change from a fluid to a solid or semisolid (gel) state as the proteins many cooked foods depends on the coagulative properties of egg proteins -eggs bind foods together, thicken them •ex such as custards, omelets and puddings, cakes and cookies. - In baked goods, egg proteins permeate the dough and coagulate -contribute to the firmness of the crumb and assisting the gluten to hold the volume attained (leavening) -In a custard or pudding, this coagulative property is responsible for the custard texture and mouthfeel- the main thickener in most custard and the yolks make them smooth and rich

What about cholesterol found naturally in foods?

Cholesterol limits previously were 300mg/day, have been removed from the most recent Dietary Guidelines for Americans Limited evidence that dietary cholesterol in low saturated fat foods increases risk of CVD Many foods which are high in saturated fat are also high in cholesterol People who enjoy foods like shrimp and eggs that are somewhat high in cholesterol but NOT excessive in saturated fat CAN include them within overall healthful eating habits

Egg preparation techniques

Coddled -A coddled egg is an egg gently cooked whole in a small dish in a hot water bath •Fried- egg white is always fully cooked -over easy- Cooked on both sides; the yolk is runny and the egg white is fully cooked -over medium -Cooked on both sides; the yolk is cooked through but soft and near liquid at the center. over hard or over well- Cooked on both sides all the way through, with the yolk intact. -sunny side up- Cooked on one side only, until the egg white is set, but the yolk remains liquid.

Yolk color

Color -Yolk color varies w/ hen's diet -Four bright carotenoid pigments: Lutein Zeaxanthin Cryptoxanthin Carotene

Lipids

Definition: -Nonpolar, water insoluble compounds composed of carbon, hydrogen, and a small amount of oxygen -Fats and oils are both lipids -All lipids are commonly called "fats" Fat is solid at room temp. - usually animal derived (except coconut and palm oil, cocoa butter) Oil is liquid at room temp. -usually plant derived (except fish oil)

Leavening/Foaming

Egg foams require agitation to denature the egg white protein -Albumin unfolds, trapping air bubbles Stability- sugar and acid increase foam stability Volume: Room temp. eggs increase Fluid- increases, decreases stability Fat: decreases Salt decreases

Emulsifying agent

Compound containing both polar and non-polar groups so that it drawn to the interface between the two phases of an emulsion to coat the surface of the droplets emulsifiers: Egg yolk Lecithin Mono and diglycerides

Egg substitutes

Concern over the cholesterol content of egg yolks has prompted the development of egg substitutes • The color of the final product depends on the inclusion of a coloring agent in the formulation -because the yolk is replaced. Egg substitutes are available in either the frozen form or a fresh, fluid product -Not identical to whole eggs in their potential uses •Very low calorie since they are primarily colored egg whites

Interesteritifcation

Conventional margarines: 9-23% SFA and 15-28% TFA's Margarine w/ Fractionization/Interesterification fats: 32% SFA and 0 TFA's

Essential Fatty Acids

EFAs must be obtained through diet because the body cannot make them There are 2 major classes of fatty acids -omega 6: the omega-6 fatty acid linoleic acid (LA), and its derivatives, gamma-linolenic acid (GLA) and arachidonic acid (AA) -omega 3: the omega-3 fatty acid alpha-linolenic acid (ALA) and its derivatives, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)

grading method two: haugh units

Egg quality can also be determined by breaking the egg out of the shell • Freshness of an egg detected by cracking it open onto a flat surface & looking at height of thick albumen • Fresh egg whites sit up tall & firm, Older ones spread out • A special micrometer measures the height in Haugh units of the thick albumen in the white in relation to the weight of the egg

Egg quality

Egg quality declines continuously after laying • Changes depends on the conditions under which eggs are stored and the length of storage • Changes occur in a predictable fashion and are clearly visible Vitaline membrane around yolk weakens with age •Yolk flattens •Breaks more easily -Harder to separate yolks from whites

Grading method one: candling

Eggs are candled to check for cracks, air cell size, and egg white spreading Egg grades are determined Current automated mass- scanning equipment used by most egg packers detects eggs with cracked shells and interior defects

Egg safety

Eggs can provide an excellent medium for the growth of microorganisms. -Care must be taken to avoid external contamination (sanitary conditions). Salmonella enteritis infects the yolk of the egg while the egg is forming— before the shell is made • Salmonella can infect the egg during unsanitary storage/processing Use of pasteurized egg products avoids this source of infection • Per food code, eggs that have not been pasteurized should be cooked to a temperature of at least: - 145F for immediate service, 155F for hot holding Prompt refrigeration of eggs and egg- containing dishes or holding of hot egg dishes at or above 60°C (140°F) should be the rule at all times Commercial farmers- Eggs are gathered soon after laying, refrigerated, washed w/ detergent •Held at 45°F or below during transport and sale •Generally if you buy cold eggs and keep them cold; will keep for up to 5 weeks • Cook egg dishes to kill Salmonella enteritidis , at least: -145F/155°F (yolk and white will be firm) • Consider using pasteurized eggs if you will be undercooking eggs. Pasteurized eggs MUST be used when serving high risk populations (elderly, children <3, immunocompromised)

Functions of eggs in food

Emulsifying •A good emulsifier •Have polar groups to blend with the watery phases •Have non-polar groups to pull the molecules toward oil •Egg yolk - Contains lecithin •Thicken & stabilize salad dressings, sauces, mayonnaise

Emulsions

Emulsion Oil-in-water emulsion- (more common) Droplets of oil dispersed in water Mayonnaise, milk, cream, egg yolks Water in Oil emulsion (less common) Droplets of water dispersed in oil Butter, margarine Emulsions in Gas phase- emulsifier added to cake batter disperses the air bubbles resulting in a finer crumb Eggs, Mono and diglyerides (commonly added to commercial baked goods)

Fractionation/ interesterification

Enzymes to split fatty acids from glycerol, then reorganizes them on glycerol to form different triglycerides with less tendency to form coarse crystals. Usually blend hard fats (palm oil, fully hydrogenated oil) with liquid oils to produce fats with intermediate characteristics.

Olive oil

Extra virgin, virgin-oil only from first mechanical pressing of olives - No oils can be added from other sources - No heat or solvents From olives 6-8 months old; cleaned, crushed, ground into paste, gently pressed to squeeze oil out International Olive Council - Extra virgin oil-less than 0.8% free fatty acid (olives first pressing) - Virgin- less than 2% free fatty acid (cold pressed) - "Light" olive oil- more refined, ultra-filtrated, bland, higher smoke point, can use for baking, deep-frying

Structure of Fats in Foods- monoglycerides

Fats in foods can be classified by the number of fatty acids esterified to the glycerol molecule If one fatty acid is esterified to the glycerol molecule, the compound is designated as a monoglyceride

Review

For optimal long-term health a diet should include a proper balance of all nutrients including fat There are different types of lipids, some essential and others not required from foods Goal -Consume mostly unsaturated fats -Limit amount of saturated and trans fats A plant-based diet plentiful in whole grains, fruits, and vegetables, with some low-fat dairy and lean meats, poultry, fish, and vegetable oil. This diet will be high in fiber and lower in saturated fats, trans fats, and dietary cholesterol

How do manufacturers lower TFA's

Fractionization/Interesterification - hardening liquid oils by adding saturated fatty acids with a higher melting point to transform an oil mixture to a solid fat for a variety of food processing applications. (Instead of hydrogenation) - Fractionation: physically separates saturated fatty acids from mono- and polyunsaturated fats. Using Tropical Oils: Coconut, palm, palm kernel oils -High sat fat, high melting point, firm texture - Can replace hydrogenated fats - contain approximately 50% saturated fatty acids

Functional Roles of Fat

Heat transfer- fat acts as a medium for heat ex. sautéing, pan-frying, deep frying Tenderness/Shortening power- reduces gluten formation ex. Biscuits, pastries, cakes, cookies Color-makes milk white and butter yellow Flavor- the taste is very difficult to duplicate, absorbs flavor (ex garlic in oil) Plasticity-ability of solid fat to be molded into shapes (ex. icing) Emulsification-combination of oil and water (ex. Butter,milk)

Effects of processing on fats

Hydrogenation: addition of hydrogen atoms to unsaturated fatty acids - prevents rancidity - raises melting point (oil fat) - lose health benefits of unsaturated fats Trans Fatty Acids: unsaturated fatty acids change shape during hydrogenation, heating - Becomes solid at room temp - ex: margarines, deep-fried foods, chips, etc. - associated with CVD risks similar to or greater than saturated fats

Interesterification of fats

Interesterification is a method used to change the fatty acid composition of fats and oils by hydrolysis of fatty acids. Excess amounts of glycerol are added to a mixture of vegetable oils. Highly saturated hard fats are combined with liquid oils resulting in zero trans fat for margarines and shortening.

Bloom

Just before laying an egg, the hen adds a protective layer called "egg bloom" or cuticle to the outside of the egg. -seals the shell pores -prevents bacteria from getting inside the shell -reduces moisture loss from the egg - -ALL designed to make the egg last longer. commercial eggs are washed right after collection -destroys the protective egg bloom -Some commercial packers spray shells with a thin film of mineral oil - that's why grocery store eggs sometimes appear shiny. • Eggs that have their protective bloom will last for months, -washing them right before cooking is a good idea -Can remove feathers or debris by brushing them off

Fats and oils in the marketplace: animal sources

Lard- fat rendered from pigs; used in cooking, baking; store in refrigerator Leaf lard-the premium type of lard; fat from abdominal cavity around the kidneys Tallow-from beef cattle, sheep All are 100% fat

Meringues

Meringues are egg white foams containing sugar • The quantity of sugar determines whether the meringue is classified as a soft or a hard meringue - Hard meringue- 4 T sugar per 1 egg white, dry and brittle when baked - Soft meringue- 2 T sugar per 1 egg white, soft when baked, topping on pies Leaking can be caused by failure to coagulate all the proteins in the foam -Sometimes seen in soft meringues • Beading is formation of droplets of a golden-brown color when a finished pie stands for a while -From over-coagulation of some of the protein at the surface of the baked meringue -Soft meringues must be eaten within 24 hours unless gums are added to stabilize them

Margarine

Minimum 80% fat from oils (soybean, corn, canola, cottonseed, sunflower oil) Blended w/ salt, milk solids, emulsifiers (monoglycerides, diglycerides), colors and flavorings added ~100 kcal/T; same as butter No cholesterol Not necessarily healthier due to trans fats from hydrogenation Stick (hard) margarine can replace butter 1:1 in recipes...but it may contain trans fats

Size or weight class of eggs

Minimum net weight per dozen -Jumbo: 30 ounces •Extra Large: 27 ounces •Large: 24 ounces •Medium: 21 ounces •Small: 18 ounces •Peewee: 15 ounces •Eggs used in recipes are usually large eggs. Assume a large egg in a recipe that size is not specified

H5N1 avian flu

Most cases of AF in humans resulted from direct or close contact with infected poultry. • cooking methods already recommended by the USDA and the FDA for poultry and eggs to prevent other infections will destroy AF viruses as well.

Health risks of trans fats

Nutrition research demonstrates a positive linear relationship between dietary intake of trans fatty acids and - Serum low-density lipoprotein (LDL) - Cholesterol and total cholesterol (TC) levels - Increased risk for cardiovascular disease The FDA published a final rule on July 11, 2003, that amended food labeling regulations requiring that trans fat be listed on the nutrition label The ruling was made based on research that demonstrated a positive relationship between dietary trans fat intake and CHD

Fats and oils in food products

Nutritional properties: Fats contain the fat-soluble vitamins A, E, D, and K. It is calorically dense: 1 gram of fat is equal to 9 kcal. ~100 kcals per Tbsp Overconsumption of certain fats contribute to obesity, diabetes, heart disease Dietary fat should be 20-35% of the diet in adults, 30-35% in children 2-3 years of age, and 25-35% in children and adolescents 4-18 years of age. <10% from saturated fat Keep trans fat intake as low as possible Fats are essential nutrients- Deficiency causes failure to thrive in children (stunted growth), eczema Children <2yrs- fat should not be restricted- critical for brain growth

Physical and chemical properties

Omega 3 fatty acid: The first double bond is at the third carbon from the omega end Omega 6 fatty acid: The first double bond is at the sixth carbon from the omega end

Sources of Omega Fatty Acids

Omega-3 and omega-6 fatty acids are considered essential fatty acids. Omega-9 is not essential. Omega-3 is found naturally in vegetable oils, such as olive oil and canola oil. Omega-3 is especially high in flaxseed oil and oily fish Foods high in omega-6 are vegetable oils, including corn oil, cottonseed oil, sunflower oil, and soybean oil.

Preservation

Pasteurization-must be done if eggs are sold outside their shells -Hold liquid whole eggs at 61°C (142°F) for 3.5 minutes -Kills microorganisms without denaturing the egg protein • Drying- used by food industry for use in manufacturing other foods • Freezing-whites freeze well; thaw and use any way that fresh whites would be used -Frozen yolks form gels making them too viscous for many uses -Salt or sugar can be added to prevent gelation Pasteurization -Eggs can spoil rapidly once they are removed from their protective shells -Pasteurization of eggs marketed outside their shells is necessary to ensure the safety of these products •Do not store pooled eggs -Pooled eggs are raw unpasteurized eggs that have been cracked and combined together.

Fats and oils in the marketplace: plant sources

Plant sources: olives, palm berries, palm kernels, cottonseeds, soybeans, rapeseeds, corn, sunflower seeds, safflower seeds, grapeseeds, coconuts, peanuts, walnuts, macadamia nuts, rice bran, cacao beans Most are high in MUFA, PUFA's Cocoa butter, coconut oil, palm kernel oil high in saturated fat

Poached eggs

Poached eggs should have the white congealed tenderly surrounding the yolk -Slightly coagulated and still not set— even at the edges • The FDA recommends poaching eggs 5 minutes in boiling water -To assure destruction of Salmonella enteritidis Whites of lower-quality eggs spread and give a jagged, feathery appearance when poached -The yolk tends to separate, pull away from the white or break when the egg is spooned from the water •The addition of acid when poaching low-quality eggs speeds coagulation and minimizes spreading

Shortening

Previously made from hydrogenated oils; no water Now they are "trans fat free" May contain artificial flavor, color May contain added monoglycerides and diglycerides for excellent emulsification properties Good plasticity- ability of a fat to be spread or creamed 7/8 cup shortening = 1 cup butter Crisco introduced in 1911- economical alternative to butter & animal fats

Scrambled eggs

Prior to heating, milk usually is added to dilute the egg mixture •Sufficient beating is done to mix the egg albumen, yolk, and milk completely—but not create a foam •Overcooking scrambled eggs with added liquid will cause syneresis as the protein draws tighter Without added liquid, the egg mass can become quite tough with overheating •Eggs held on a steam table for an extended period, begin to turn greenish-gray as ferrous sulfide forms

Egg preparation techniques cont.

Quiche-pastry crust filled with eggs, milk or cream, and cheese, meat, seafood or vegetables. Quiche can be served hot or cold •Scrambled-eggs stirred or beaten together in a pan while being gently heated •Soufflé-A soufflé is a light, fluffy, baked dish made with egg yolks and egg whites • Hard and soft boiled- -HB- eggs are cooked so that the egg white and egg yolk both solidify SB- eggs may leave the yolk, and sometimes the white partially liquid • Frittata- Italian dish similar to an omelette or crustless quiche added meats, cheeses or vegetables • Poached- submerging in liquid at a low temp- tender product

Refining food fats

Refining-after extraction -refining removes most of the flavor (becomes a neutral taste) - also removes undesirable gums, proteins, ketones which can impact shelf life, smoke point, clarity and flavor Degumming-via steam distillation, removes gums, free fatty acids Neutralizing-free fatty acids are removed, produces a stable oil with good shelf life Bleaching-by filtering through activated carbon Deodorizing- removes off-flavors, aromas - Olive oil is not deodorized

How food fats are extracted

Rendering-first step in production of lard (from pigs or tallow from beef cattle and sheep) is extraction of fat from tissues; steamed to liquefy - Hot, liquid fats separated from water - Antioxidants may be added Cold Pressing-mechanical pressing of seeds or olives at ambient temperatures - Excellent purity, have full flavor from the plants they were pressed (ex sesame) Expeller Pressing- mechanical pressing of seeds or olives with high pressure, may generate heat, oils still retain most of their flavor Hot Pressing-steam or hot water to heat seeds to 158° F; loss of natural flavor, usually also use chemical solvent (usually hexane) - Majority of commercial vegetable oils are made this way - After extraction, the solvent is evaporated out by heating the mixture

Fat alternatives

Replacing fat with conventional ingredients -water, air, nonfat milk, soy protein Artificial fats -Simplesse: protein-based, can't be used in cooking; used in ice cream, smooth mouthfeel, 1.3calories/gram Olestra/Olean: sucrose polyester (sucrose + 8 fatty acids) can be used in cooking, frying, baking indigestible: causes GI problems in large amounts fat-soluble vitamins & phytochemicals in food also not absorbed

Shell color

Shell color comes from pigments in the outer layer of the shell -the breed of hen determines the color of the shell. Among commercial breeds, hens with white feathers and ear lobes lay white- shelled eggs - hens with red feathers and ear lobes lay brown eggs - brown-egg layers are slightly larger birds and require more food- usually more expensive

Shell composition

Shell membranes -Inner & Outer Air Cell - Between two shell membranes Shell - 11-12% of egg weight -Composed of calcium carbonate; cuticle or bloom bloom is the natural coating or covering on the eggshell that seals the eggshell pores

Fatty acids vary in length

Short-chain fatty acids: <6 carbons Liquid at room temperature Medium-chain fatty acids Six to ten carbons Long-chain fatty acids 12 or more carbons Most common type of fatty acid in foods Usually solid at room temperature

Simple Fat

Simple lipids: lipid comprised of glycerol and fatty acids Glycerol: alcohol containing 3 carbon atoms, each of which is joined to a hydroxyl group Fatty Acid: organic acid containing between 4 and 24 carbon atoms

Smoke Point

Smoke point: temp at which a fat or oil begins to emit traces of smoke Important for frying food When fat smokes, chemical breakdown begins-producing acrolein & fatty acids Vegetable oils except olive oil have high smoke points, ~450°F; animal fats ~375°F Butter/margarine decompose at lower temps Smoke point is lowered with continued use of the same oil and increased numbers of food particles, so clean fat fryers and add 20% fresh fat Shortenings are not appropriate for frying b/c of amounts of mono- and diglycerides that can quickly undergo lipolysis. Acrolein- The irritating, volatile aldehyde formed when a glycerol is heated to the point at which two molecules of water split from it

Custards

Stirred and baked custards are sweetened milk mixtures—thickened with egg Usually flavored with salt and vanilla Whole egg proteins provide most of the thickening • Milk proteins add an insignificant increase viscosity

Egg storage

Store eggs in the refrigerator < 45 degrees • Why do we need to refrigerate eggs in the US? Unpasteurized eggs should be stored on the bottom shelf, caution with cross contact in the refrigerator

Butter cont.

Sweet cream butter- made from pasteurized fresh cream - the word "sweet" is used mostly to distinguish it from those cultured or soured cream alternatives. Cultured or soured cream butters have a tangy, slightly sour taste, and are made with added cultures or fermented - European-style butter is typically produced this way, while American-style butter is typically sold as sweet cream butter Clarified: the water and milk solids have been removed, leaving pure milkfat; clear; sauces, dips, etc. Ghee: clarified butter that's cooked longer. Milk solids are caramelized then strained for a rich, nutty flavor- also raises smoke point Brown butter- made by heating butter over low heat until milk solids caramelize to desired color

Shell structure

Two shell membranes enclose the entire contents of the white and yolk of an egg many tiny pores that permit passage of gases or tiny microorganisms into and out of the shell

types of emulsions

Temporary -Little or no emulsifying agent, require agitation to create emulsion -will separate quickly after agitation stops, "separates on standing" Ex. Oil and water, oil and vinegar Semi-permanent: -Basic emulsions, usually vinaigrettes which include a stabilizer and hold longer than a temporary emulsions but not indefinitely such as permanent emulsions. -For example Dijon mustard vinaigrette. Permanent - Emulsion containing an amount of emulsifying agent sufficient to enable it to remain intact during ordinary handing and use - Very viscous and stable Egg-yolk Milk Commercial salad dressing Mayonnaise

Does the dietary guidelines promote a low-fat diet?

The 2015-2020 Dietary Guidelines does not encourage a low-fat diet. - recs for <35% of total calories per day from fat. the 2015-2020 edition encourages eating styles that emphasize unsaturated fats and are low in saturated fat. - keeping saturated fat consumption to less than 10% of calories per day. - However, it is important to note that replacing saturated fat with added sugar and processed carbohydrates will not reduce the risk of cardiovascular disease.

Saturated and unsaturated fatty acids help shape foods

The carbon atoms sort of zig-zag; not in a straight line The double bond has a huge effect on the shape of the molecule There is little difference in the shape of the trans molecule, compared to the completely saturated molecule

Eggs by design

The diets of chickens can be manipulated to alter components of their eggs • Such as elevated levels of Omega-3 fatty acids Eggs lower in saturated fat and cholesterol-hens fed a canola oil-rich diet; eggs must be at least 25% lower in sat fat and cholesterol Omega-3 eggs- hens fed flax -300 mg omega-3 per egg -185 mg cholesterol, 4 g fat, 1 g sat fat • Free-range eggs- hens raised in outside enclosures during the day, in a barn at night • Cage-free eggs- hens raised on the floor of a building instead of in cages • Organic- organic vegetarian feed; no antibiotics; no hormones Buy your eggs local-

Fatty acids- melting point

The melting point is the temperature at which a fatty acid is transformed from a solid to a liquid This is significant in determining specific applications in food preparation Saturated fatty acids have higher melting points than their counterparts containing a double bond The higher the degree of unsaturation- the more double bonds- the lower the melting point - at double bonds, configuration is either cis or trans - if the double bond is in the cis form, the melting point is much lower than when the molecule has a double bond in the trans form longer chain FA's- higher melting point short chain FA's- lower melting points

Egg quality

The quality of eggs can be graded in or out of the shell

Egg structure and nutrient comp.

There is much more white than yolk —about twice as much by weight Nutrient properties: A large egg provides: -about 72 calories -about 6 grams of protein (3.6 grams comes from the albumen/egg white, 2.7 grams found in the yolk) - Fat provides 50% of the calories in eggs, comes from the yolk, 186 mg Cholesterol Loaded with vitamins -B12, riboflavin, folate, and the fat-soluble vitamins A,D, and K. -Some minerals- calcium, iodine, iron, phosphorus,selenium, and sodium two carotenoids that act as antioxidants and are thought to be important to eye health -lutein and zeaxanthin • Eggs contain the highest amount of choline in any single food -a micronutrient essential for fat breakdown to produce energy Diets lacking choline may lead to fatty liver and muscle damage

Structures of Fats in Foods- Triglycerides

Triglycerides are composed of three fatty acids esterified to the glycerol molecule This is the max number that can exist in the compound

Quality and grading of eggs

U.S. Grade AA - HIGHEST QUALITY- eggs provides thick firm whites when cracked; the yolks are high, round, and practically free from defects; and shells are clean and unbroken. • U.S. Grade A eggs provides characteristics of Grade AA eggs except that the whites are "reasonably" firm. • U.S. Grade B eggs provide thinner whites, and when cracked, the yolks will appear wider and flatter than the eggs of higher grades.

Egg grading

USDA Grading is voluntary Best-quality eggs -USDA Grade AA -USDA Grade A • These grades are sold at supermarkets Lowest Grade - USDA Grade B •Available to food service establishments •Not sold directly to consumers

Plant breeding and biotechnology

Vegetable seed oils have been developed by traditional plant breeding, mutations, and gene modification for decades to improve yield as well as functional and nutritional qualities. An example of plant breeding to change the fatty acid composition is the elimination of the undesirable erucic acid from rapeseed resulting in the popular canola oil Oils can be developed for desirable fatty acid profiles

Foam stability

Volume -Contamination of whites with even a trace of yolk has a negative impact on the volume -Water has a positive effect on volume of egg white foams—while they are being beaten •Lost almost immediately because of lack of stability

Formation

When hens first begin laying, their eggs are quite small, but the size increases as they mature

Butter alternatives

Whipped butter is whipped with air or nitrogen gas to increase spread-ability - Each tablespoon has half the weight and calories of butter; ~50 cals/Tablespoon Low calorie butter alternatives- dried powder extracts from butter with no fat - Molly McButter, Butter Buds- these are starch-based Powdered butter- made from dehydrated butter pressed with milk solids

Hydrogenation

Why hydrogenate? Partial hydrogenation transforms liquid oils into more solid fats to improve shelf life and make fat more plastic and workable Raises the melting point Hydrogen atoms are added to unsaturated fats Double bonds are eliminated as fatty acids become saturated w/ hydrogen Some double bonds remain but hydrogen atoms end up on different sides of chain - these are trans fatty acids

Hydrogenation

addition of hydrogen atoms to an unsaturated fatty acid causing the double bonds (unsaturated) to become single bonds (saturated) Hydrogenation turns vegetable oil into shortening

Structures of Fats in Foods- diglycerides

also called diacylglycerides, contain two fatty acids esterified on one glycerol molecule may be on the two terminal or on two adjacent carbon atoms of glycerol

Saturated fat

contain all the hydrogen atoms it is chemically possible for them to have- "saturated in hydrogen" - a fatty acid with NO double bonds is classified as a saturated fatty acid

Unsaturated fat

contain one or more double bonds- "unsaturated in hydrogen" - contains ONE double bond= monounsaturated - TWO OR MORE double bonds = polyunsaturated

Fatty Acids

higher ration of carbon and hydrogen to oxygen than in carbohydrates and protein -very energy dense -9 kilocalories per gram of fat 20 different fatty acids with varied length, saturation and shape The fatty acids determine the physical characteristics of the lipid

Triglyceride- Most common lipid

most common type of lipid molecule in food fats - 2 key components: glycerol + 3 fatty acids constitute about 95% of the lipids found in foods. These include fats and oils

Winterizing oils

process of chilling an oil to precipitate, filter, and remove any fat Removes some oils with high melting points So oils can be kept chilled without having fat crystals form- so they can remain clear and pourable when cold

Phospholipids

similar in structure to triglyceride 2 fatty acids are attached to the glycerol molecule one of the fatty acids is replaced by a compound containing phosphorus - makes the phospholipid soluble in water Foods naturally high in phospholipids: egg yolk, liver, soybeans, wheat germ Ideal emulsifiers, widely used in food industry because it has hydrophobic and hydrophilic properties (disperses in water or oil)

To reduce acrylamide

to decrease the level of acrylamide in their diet. When frying frozen French fries avoid overcooking, heavy crisping or burning. Toast bread to a light brown color rather than a dark brown color. Cook cut potato products such as frozen French fries to a golden yellow color rather than a brown color. Do not store potatoes in the refrigerator, which can increase acrylamide during cooking.

Fatty acids vary in shape

unsaturated fatty acids form two different shapes Cis= hydrogens are on the same side of the double bond Trans= hydrogens are on opposite sides of the double bond