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Material Type: Lab; Class: FOOD CHEMISTRY; Subject: FOOD SCIENCE; University: University of Florida; Term: Unknown 1989;
Typology: Lab Reports
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Laboratory 9 Protein chemistry - foaming properties Introduction Proteins are used extensively in the food industry for their functional properties (i.e., gelation, foaming, viscosity) as well as for their nutritional properties. Protein as a component in foods can also influence their properties of texture, flavor, etc. Such an example is milk proteins and their contribution to cheese, yogurt, ice cream, etc. and egg white proteins for foams. The ability of a protein suspension to form a stable foam is dependent upon its physical form, the pH of the suspension and on the presence of other constituents. Proteins are surface active. This means they have the ability to interact both with air and water. The hydrophobic parts of proteins interact better with air compared to the hydrophilic parts, which favor interactions with polar solvents such as water. Since most of the hydrophobic groups of a protein are buried in its interior it is important to properly unfold (open up) the protein to produce a good foam. This is normally done by mechanical action where the protein solution is whipped, thus allowing for more contact of air to the protein which makes it favorable for the protein to open up and expose its hydrophobic groups to the air phase. During this process the protein will eventually form a strong cohesive network around air pockets, with its hydrophobic groups sticking into the air phase and the hydrophilic into the water phase. Different protein types can differ tremendously in their ability to form strong and stable foams. Also, by changing the environment around the protein (pH, salt conc., temperature etc) the properties of the protein can be greatly affected. The following lab will examine some of the variables that are important in obtaining a stable foam with acceptable overrun (foam volume). Materials The instructor will assign to you one of the following protein sources:
Determine: a) Percent overrun = percent increase in volume of the material: b) Foam stability = Relative difference in % overrun between 0 and 15 min: Foam stability = % Overrun after 15 min % Overrun after 0 min Questions for discussion and conclusion