Change pH- further suppress charge- associate- molecular weight of aggregate too high to staty in solution --> suspension- precipitation
In the case of starch and proteins, which is a common mechanism for aggregation?
How can hydrophobic attraction affect solutions?
Hydophobic attraction can also be a menas of large polymers associating to form colloids (casein micelles) and/or gels- or a combination of multiple forces
How can the associations in solution result in problems?
These associating fores can result in major practical problems, especially in terms of organic waste strems from food processing operations
A classic example is waste water from potato peeling operations
Here, the waste stream will contain some protein, soluble starch, pectin, pigments, sugars and cellular debris- molecular associations take place which result in a colloidal dispersion which makes water treatment very diccigult as the dispersion will not settle out
How does one control biological oxygen demand (BOD)?
A common method of control is to convert these colloidal solutions into suspensions
This is usually done by addint coagulating salts to modify the charge of the colloids to facilitate
The formation of larger groupings of molecules (Flocs) to produce a suspension which can settle out
What does flocculation do?
Flocculation alows organic material to be separated from the waste stream- reducing BOD and pollution
What is another way of forming colloidal solutions?
Another means of forming colloidal solutions is through the forced interaction of molecular systems having strong hydrophilic and hydrophobic character
What happens at the interface of water and air?
At the interface, hydrophilic water comes into forced contact with hydrophobic air
This forces water into a structured state in such a way as to minimize the free energy associated with this forced interaction
What results from the surface of water having a different arrangement than the bulk solution?