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Protective Colloid
A protective colloid is a lyophilic colloid that when present in small quantities keeps lyophobic colloids from precipitating under the coagulating action of electrolytes. Need for protective colloids When a small amount of hydrophilic colloid is added to hydrophobic colloids it may coagulate the latter. This is due to neutralisation of the charge on the hydrophobic colloidal particles. However, the addition of large amount of hydrophilic colloid increases the stability of the hydrophobic colloidal system. This is due to adsorption. When lyophilic sols are added to lyophobic sols, depending on their sizes, either lyophobic sol is adsorbed in the surface of lyophilic sol or lyophilic sol is adsorbed on the surface of lyophobic sol. The layer of the protective colloid prevents direct collision between the hydrophobic colloidal particles and thus prevents coagulation. Examples Lyophilic sols like starch and gelatin act as protective colloids. Measurement of protective acti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyophilic
Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature Food drying, dehydration process that involves freezing the product and lowering pressure, thereby removing the ice by Sublimation (phase transition), sublimation. This is in contrast to dehydration by most conventional methods that evaporate water using heat. Because of the low temperature used in processing, the rehydrated product retains many of its original qualities. When solid objects like strawberries are freeze dried the original shape of the product is maintained. If the product to be dried is a liquid, as often seen in pharmaceutical applications, the properties of the final product are optimized by the combination of excipients (i.e., inactive ingredients). Primary applications of freeze drying include biological (e.g., bacteria and yeasts), biomedical (e.g., surgical transplants), food processing (e.g., coffee), and Food preservation, preservation. History The Inca were freeze dry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
