Nutrition 211 test 3

Effect of acid on casein

- it will coagulate in the presence of acid. Casein proteins will denature and precipitate out.

albumin denatures around

140 degrees

egg yolk denatures around

149 degrees

Whey proteins denature and precipitate at

158 degreees F.

Soft meringue-

2 tbsp sugar per egg white. It is more what you will see on a pie. Cooked at higher temperature for a short time.

Quality grading voluntary

AA, A, B

shell

It is made of calcium carbonate and has pores that enable gas exchange. It is protected by the cuticle which is a substance composed of organic material that kind of fill in the pores.

Process and goals of pasteurization

Milk is a good medium for bacteria, so pasterurization serves to kill all pathogenic bacteria. It also inactivates spoilage enzymes. It is done by heating the milk to a temperature that can kill the bacteria.

• Yolk-

Rich in phospholipids, fat-soluble vitamins, cholesterol, iron. There are different proteins in egg yolk. These include vitellin (lipoprotein used as an emulsifier), phosvitin (phosphoprotein), and livetin (a sulfur containing globular protein).

Three steps in the production of cheese

Step one: precipitate milk proteins. This is done by coagulation. Coagulation is achieved either by enzymes or acids. Cultures of microorganisms serve as starters. These bacteria will start eating lactose and produce lactic acid which reduces the pH. The pH must be reduced for best action of rennin. This influences the flavor, color, and texture during ripening. Reducing the pH allows for the coagulation of casein. Rennin cleaves capacasein. For enzyme coagulation, the milk is heated, the temperature of the milk when the cultures are added can influence cheese texture. It takes about 1-3 hours for curds to form. Acid coagulation occurs when you add acid to milk or inoculate milk with bacterial culture that makes acid. This takes 4-16 hours for curd formation. The casein is separated from the whey. These are higher moisture cheeses that are generally not aged.

cheese

The curd or coagulated proteins (casein) of milk induced by enzymes or acid

Green ring-

The iron in the egg yolk can form ferrous sulfide in the presence of high temperature/long cook time. Prevent this by cooking at low heat for a short time.

Low Temperature Long Time Pasterurization-

This is also called vat pasteurization. It heats it to 145 degrees F for 30 minutes. It is stirred the whole time. It is most commonly used for cultured milk products.

albumin

This is the egg white. It is mainly water and protein. Also has some vitamin B12, riboflavin, biotin, selenium, iodide, and zinc. The main proteins are ovalbumin, ovotransferrin, and ovomucoidprotein. Ovalbumin is the main protein in the egg white and it is easily denatured and this contributes to the structure of cooked egg products. Ovotransferrin binds iron and inhibits growth of bacteria dependent on iron. Ovomucoidprotein is resistant to heat denaturation and contributes to viscosity. It also has lysozyme and avidin (binds biotin to prevent microbial growth).

air cell

This is the phenomenon that occurs when the egg is laid. As the egg ages, the air cell increases in size. The egg loses carbon dioxide and water through the shell.

Acid coagulated cheese-

This is when acid is added to milk to lower the pH or bacterial cultures that produce acid are added. They lose some calcium in the whey.

Egg substitutes-

This is when you substitute things mixed in with the eggs. For example, you can omit the egg yolks, replace egg yolks with vegetable oil, and reduce the egg yolks.

shell membrane

Two membranes between the egg white and shell that protect against bacterial invasion.

Water-in-oil emulsion

Water droplets suspended in lipid phase (butter and margarine)

Emulsion-

a system consisting of one liquid dispersed in another liquid

Plasticity

ability of a solid fat to be molded or shaped; it is related to temperature of the fat. Plastic fats are valuable for their spreading, creaming, and pastry ability.

Way to coagulate casein

add acid such as lemon juice, lime juice, or tomato juice

Reduce coagulation by

adding acid to milk (ATM)

Listeria monocytogenes-

bacteria that can grow at refrigerated temperatures

Basis for milk grades

bacterial count

Creaming can occur

because it has the ability to coagulate. The separation of fat globules from the proteins causes the fat to float to the top and "cream."

Milk is an emulsion

because it is has water and fat globules blended together

Hydrolytic rancidity of fat-

breaking chemical bonds by adding water; yields glycerol and free fatty acids

Skin-

caused by surface evaporation of water, which results in increased concentration of casein, fat, and mineral salts

Oxidative rancidity

chain reaction on unsaturated portion of fatty acids where an H is lost and a free radical is formed

adding sugar increases

coagulation temperature

salt/acid decreases

coagulation temperature

Egg white and egg yolk have different

coagulation temperatures.

Step two

concentrate the curd. The whey is separated from the curds, primarily drained via gravity. Methods to remove more whey include cutting and cooking/heating. Cutting increases the surface area. While the cooking/heating evaporates the whey.

Consistency of a lipid will affect its functional properties in food

consistency will affect the spreadability, creaming, and pastry (emulsion, aeration)

Enzyme coagulation

enzymes added to the milk; temperature of milk when cultures added influences cheese texture

Ultrahigh Temperature

for aseptic packaging that is essentially sterile until opening. It is heated to 280-302 degrees F for about 2-6 seconds.

Foam-

gas bubbles that are dispersed in a solid or liquid

AA graded eggs

have a high proportion of thick albumin, yolk is upstanding and centered, and a small air cell

Way to coagulate whey

heat until they become insoluble, mesh with calcium phosphate, and precipitate on bottom and sides of the pan

Hard meringue-

higher percentage of sugar (4 tbsp per egg white). It is more like the cookies. Cooked at much lower temperature for a long time.

role of aging

intensifies the flavors. There is continued enzyme activity, bacterial growth, and moisture loss that concentrates flavors.

High Temperature Short Time

is heated to 161 degrees F for 15 seconds. It it the most common method for fluid milk.

Temporary emulsion-

least viscous and stable and will separate on standing

Homogenization

mechanical process that prevents the separation of water and fat. This prevents creaming. It is done by forcing milk through small openings and breaking up pthe fat globules

Permanent emulsion

most viscous and stable; does not separate

Oil-in-water emulsion-

oil droplets suspended in aqueous phase (milk, cream, egg yolks, salad dressings, mayonnaise, cheese sauces)

Why pasteurization occurs before homogenization

pasteurization inactivates some spoilage enzymes so it is good to reduce those before homogenizing when the milk can go rancid quicker

Milk coagulation in food preparation

polyphenolic compounds such as vegetables (potatoes, fruits, coffees, teas) as well as salf (salted meats, canned vegetables) can cause coagulation of milk

Method for hard-cooking eggs

puts eggs in pan and cover with cold water by an inch. Bring to a boil, once there, put a lid on , turn it off, and let it sit.

Step three of cheese

ripen the "green" cheese. Increasing temperature speeds ripening because more microorganisms are active. By ripening the cheese, the flavor intensifies.

egg foams

stability is affected by protein content and room temperature.

Semipermanent emulstion

stabilizers added; more viscous (Dijon mustard in dressing)

Emulsifie

stabilizers that help keep one phase dispersed in the other

In milk foams,

temperature and fat increases stability

Cage free-

the chickens are not in a 1x1 foot pen

Smoke point-

the temperature at which a fat breaks down into visible gaseous product; different smoke point for different sources of fat

Free-range

they have access to outdoor enclosure at some time during the day

Egg substitutions-

this is when you use something else in place of an egg for a recipe

Candling

visualize the interior of the egg using a light source so that the grade can be determined

Inspection-

was mandatory of all processing plants, wholesome, unadulterated, truthfully labled

parts of egg

yolk albumin shell membrane air cell shell

Food industry controls of oxidation

• Antioxidants- They will donate an H to the free C. There are some natural and synthetic ones added. • Citric acid- not an antioxidant, but it helps them work better • Chelating agents- bind trace amounts of metals.

Real steps

• Beat with electric mixer or wire whisk • Initially beat at moderately low speed until egg whites foamy • Increase speed of beating; as you continue, beating air bubbles will get smaller, finer and begin to hold shape • Continue beating until peaks are stiff and shiny, not dry • Over whipping results in dry foam, not shiny, and stable foam

General nutrient profile of milk vs. cheese

• Calcium content depends on method of coagulation • Higher sodium in cheese • Easier to digest due to lower lactose levels

Two Main milk proteins

• Casein- 80% of protein in milk • Whey- 18% of the protein

Nutrient profile of milk

• Complete protein • Rich in B-vitamins, especially riboflavin • Rich in tryptophan (niacin precursor) • Vitamins and D • Excellent source of calcium, phosphorous, potassium • Americans get more vitamin k from milk than fruits or veggies

Removing whey:

• Cutting: run grates through the cheese to increase the surface area • Cooking/Heating: evaporates whey, contributes to texture by fusing filaments of casein • Salting cheese- dehydrates the curd and results in a further extraction of whey

Three phases of an emulsion

• Dispersed or discontinuous phase- what is suspended • Dispersion or continuous phase- what is doing the suspending • Interface- the boundary between the discontinuous phase and the continuous phase

Safe storage of eggs

• Don't wash; keep in carton for moisture retention • Don't store in refrigerator door • Store for 4-5 weeks after pack date

General uses of eggs in food preparation

• Emulsifier • Binding agent • Interferes with large ice crystal formation • Clarifying (dissolve egg whites in cold liquid then heat liquid to attract proteins in liquid that make it cloudy)

Factors that affect emulsion stability (these all decrease it)

• Excessive agitation • Long storage times • Extreme temperatures (in hot temps, the heat thins the viscosity of the emulsion) • Adding excessive salt (will increase the surface tension • Significant changes in pH (proteins keep their shape at a particular pH, Outside that normal pH range will lead to unfolding of that tertiary and quaternary structure

Factors affecting milk foam stability

• Fat content- higher fat more stable, at least 30% fat • Age- aging for minimum of 3 days is more stable (becomes more viscous) • Temperature- colder is more stable (further from melting point) • Sugar- increases the stability (smaller air bubbles formed • Time- whip it long enough so that you have stretched the proteins around the air bubbles

FDA guidelines for using pasteurized milk in the production of cheese

• For fresh and soft cheese, the FDA requires using pasteurized milk • Hard cheeses can be made with raw milk if they are aged for a minimum of 60 days

Smoke point of cooking oils is lowered by:

• Free fatty acids (when we cook a lot of high moisture foods in fat, the water will accelerate the process of removing fatty acids from the glycerol backbone) • Suspended matter (little pieces of breading) • Greater surface area of fat exposed to air (frying in narrow, deeper vessel, smaller surface area exposed to air)

Factors that affect the melting points of fats

• Hydrogenation- increases melting point by changing the bonds from cis to trans • Increase of carbon length of fatty acid increases the melting point • Increase of double bonds decreases the melting point

Salmonella enteritidis

• Internal contamination: in ovary of hen • External contamination: fecal contamination

Prevention of skin formation

• Make a foam on top • Cover pot with lid • Float something in it • Low heat or double boiler

Why milk can be made into a foam

• Milk proteins stretched into thin layers when milk is agitated • Milk proteins trap air bubbles, fat particles and liquid because proteins in milk have low surface tension

Eggs sized based on the average weight of a dozen

• Pee-wee: 15 ounces • Small: 18 ounces • Medium: 21 ounces • Large: 24 ounces • X-large: 27 ounces • Jumbo: 30 ounces

Factors that affect the consistency of plastic fats

• Ratio of solid:liquid • Type of crystals • Fatty acid composition of fat • Temperature

Consumer controls to prevent rancidity

• Refrigerate • Exclude light • Exclude moisture • Exclude air

Possible problems with meringue pies

• Shrinking; prevent by overlapping onto pie crust • Weeping (syneresis): caused by underbeating or putting meringue on cold filling; loss of water • Beading: caused by undissolved sugar and overcooking, occurs on the top, looks like little drops of melted sugar, often caused by not enough beat time

Considerations for producing a high-quality deep fried fat product

• Smoke point of cooking oils • Some degradation products of frying are surfactants • Amount of fat absorbed by food • Choosing the right fat for frying

High quality meringue pies

• Spread meringue on warm filling. This starts to denature the proteins and it will heat faster in the oven.

Custard

• Stirred custards: low heat/double boiler, more a pudding texture, stir throughout • Baked custards; form gels, overcooking causes shrinking; cook long enough so it sets, but don't overcook and force the moisture out

Factors that enhance or discourage egg white stability

• Sugar- enhances foam stability because it delays foam formation, making you beat harder and for smaller air bubbles. It also helps prevents water loss from the foam. • Fluid- this decreases stability. It makes them less viscous. • Salt- this will reduce stability because it increases surface tension • Acid- enhances foam stability because it enhances denaturation and how effectively we can stretch proteins around the air bubbles. Cream of tartar is often used. Another benefit is that it enhances the whiteness of the foam. It will delay formation, but once we get it, it is more stable.

How to promote safe egg consumption

• Use egg separator • Refrigerated storage • Avoid raw egg consumption • Pasteurized eggs if making a dish with raw eggs

Steps in making an egg white foam

• Whisking breaks links between protein molecules and that denatures the tertiary structure • Unfolded proteins from films around the air cells • Heat then allows the air cells to expand and coagulate to form stable structure.

Changes of homogenization to milk

• Whiter • Coagulates easier • Greater foaming capacity • More prone to rancidity

Impact of temperature and humidity on aging

• increase the temperature to speed ripening and result in more microorganism activity • increase the humidity to increase mold growth

Adding flavor

• salting cheese • injecting with mold

Factors that affect the cooking quality of cheese

• temperature- lower temperature best, prevents toughening and oil separation • Time- shorter best, if a topping, add at end of cooking to prevent separation • Acid- can cause separation, coagulation • Alcohol- decreases boiling point of mixture, decreases curdling (fondue)