Food Science - Ch. 9
Why do some emulsions break? How can they be reestablished?
Excessive evaporation of water. It can be reestablished by replacing the water lost through evaporation during an extended heating and/or holding period.
Why is fat creamed with sugar in a shortened cake? How is a stable emulsion formed, and what does it do?
Fat and sugar are creamed together to promote fine, light textures in cakes An emulsifying agent of some type is needed to facilitate the formation of stable emulsions. A stable emulsion helps promote the fine cell size desired in shortened cakes
How does fat tenderize a baked good? Which types are most effective for tenderizing?
Fat interferes with gluten development by mixing the fat or oil with the flour so that the lipid gradually coats the surface of the gluten complex that is starting to form. A soft fat or oil
How does fat produce flakiness in a pastry? What type of fat produces flakiness? Why is pastry usually not tender? What is it about using butter or margarine vs. shortening or lard that may cause the product to be less tender?
Fat is left in pieces in a pastry dough, it melts during the baking period and flows, leaving a hole where steam collects and pushes upward against the upper surface of the resulting cell. The gluten in the pastry is denatured during baking and the cell is locked into the extended position. This results in a flakey pastry. Solid fats Pastries use solid fat which produce flakiness, melted fat produces tenderness. Butter and margarines are less tender because they have too little fat and too much water are being used compared to shortening or lard that is all fat
How can the grainy texture be ameliorated in lard?
Interesterification, diet of the pigs or genetic modification
Why is rice bran oil being studied?
It contains two types of sterols - oryzanols and tocotrienols - that are being studied intensively for possible health benefits and are significant for their antioxidant properties
Why is deep-fat frying a dehydrating process?
The intense heat of the fat on the surface of a food such as a french fry evaporates water quickly into the cooking medium. The water loss causes mass transfer to occur in the french fry
How does the degree of unsaturation affect the shortening power? How does the degree of plasticity affect shortening power?
The more unsaturation (double bonds) = the more surface area able to be covered plasticity is the result of the physical nature of these solid fats, which actually are composed of large numbers of fat crystals with oil interspersed throughout the system.
Why are some fats tempered?
To yield a mixture of crystal shapes (polymorphs)
Why is hydrogenation done? Why are trans fatty acids of importance?
Vegetable oils can be modified to liquids to solids that is suitable for use as margarines and shortenings Modifies peanut butter from it original state to a spread that remains homogenous Trans fatty acids elevate the levels of LDLs which may increase the risk of coronary heart disease
How is a bloom formed?
the result of melting of less stable crystals and recrystallization as beta crystals on the surface
How are animal fats different from plant fats, and what are sources that are used? What are the 2 omega-3 fatty acids? What is the problem with incorporating these in other products?
Animal fats are higher in saturated fatty acids and lower in unsaturated fatty acids than are plant lipid sources; in particular, plant sources as a group are higher in polyunsaturates than are animal sources (fish oils are an exception) Animal sources - beef tallow and butterfat from cattle and lard from pigs Plant sources - olives, palm fruit and palm kernels, cottonseeds, soybeans, rapeseed Docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) They produce possible fishy flavors
What helps to prevent too much fat absorption? What increases it?
At least 175C (347F) but preferably 190-195C (374-383F) Too low of a temperature
Why is fat sometimes a beneficial cooking medium? Why are butter, shortening with added monoglycerides, and olive oil not desired for frying?
Because of their ability to be heated to high frying temperatures well above the boiling temperature of water and this causes changes in texture, flavor, and color. Butter - deteriorates rapidly at high temperatures in frying and develop rancidity if stored Shortenings - smoke point rapidly drops which irritates the eyes and a detectable flavor develops Olive oil - low smoke point
What type of crystals are desired, and control of what can achieve these crystals?
Beta prime crystals control of temperature during cooling, combined with an appropriate amount of agitation
Why are fats bleached, deodorized, and winterized?
Bleaching is done to refine fats from coloring and flavoring contaminants by filtration Deodorizing is used to remove low-molecular-weight aldehydes, ketones, peroxides, hydrocarbons, and free fatty acids that would be detrimental to the aroma and flavor of fats Winterizing is used to allow oils to be refrigerated and be poured as soon as it is removed from the cold by chilling carefully to precipitate and remove fractions with high melting points that would interfere with the flow properties
Can fats be substituted for one another in a recipe? Give examples.
Butter, stick and tub margarines: 80% fat, 16.5% water Shortening, lard and oil: 100% fat Margarine can be substituted butter Tub margarine can be substituted for stick margarines and butter 90% of shortening substituted for butter, Lard can be substituted for shortening Oil can be substituted for shortening and lard
Where are the following found: cholesterol, polyunsaturated fatty acids, monounsaturated fatty acids, saturated fatty acids in a plant source, and omega-3 fatty acids?
Cholesterol - animal sources only Polyunsaturated fatty acids - safflower oil and soybean oil Monounsaturated fatty acids - olive oil and canola oil Saturated fatty acids - cocoa butter, coconut oil, and palm kernel oils Omega-3 fatty acids - fish oils
What are the 6 main functional roles of fat? How does fat function for color, flavor, and texture?
Color, flavor, texture, tenderness, emulsification, and cooking medium Butter contributes a yellow to creamy color to products Fats contribute a richness of flavor when used in a variety of food products Fat influence textural characteristics such as flakiness in baked products and fried foods crisp texture
How does Olestra work, and what can it cause?
It is a prominent fat replacer that is a hybrid between a carbohydrate and a fat classified as a sucrose polyester that cannot be digested or absorbed which doesn't provide calories to the body. It causes diarrhea and flatulence.
Why are mono- and diglycerides and beta-carotene sometimes added to shortenings? How is beef tallow sometimes used?
Mono- and diglycerides are added to improve the ability of the shortening to form an emulsion in batters and doughs. Beta-carotene added to achieve a yellow color and butter-like flavoring compounds. Small flakes of tallow are added to some shortenings during their manufacturing to help ensure that the shortening will have fine, beta prime crystals
What are some emulsifiers that are added to shortenings and what do they do? What is the best emulsifier commonly found in the home?
Mono- and diglycerides so that the fat and milk in cake batters are emulsified that results in a fine-textured cake Lecithin in egg yolks
What are the 3 main types of fat replacements? Give examples of each.
Protein-based - Simplesse contains milk and egg whites gives the mouthfeel of fat Carbohydrate-based - cellulose, maltodextrins, modified starches, and polydextrose and Fat-based - Salatrim, caprenin, and Olestra
What are the different types of butters and margarines, and how do they differ? Why do manufacturers sometimes list several oils in the ingredient list?
Stick margarines - spreads made by hydrogenating plant oils and adding water, milk solids, flavoring, and coloring to achieve a product similar to butter Soft or tub margarine - spreads with melting lower than those of sick margarines because of a higher content of polyunsaturated fatty acids Whipped margarine - stick margarine that has been whipped mechanically into fat foam; increased volume results in fewer calories per given volume It allows manufacturers to change their formulations at various times, depending on the relative cost of the oils identified in the ingredient label
What does oil do in a chiffon cake?
promotes tenderness
