Temperature effects on the ethanolic fractionation of dilute gelatin-sodium dodecyl sulfate solutions

Abstract

Gelatin is a water-soluble, macromolecular hydrocolloid protein, with a structure that is sensitive to changes in pH and temperature, since these factors influence the net charge of the protein and the strength of the intermolecular interactions. Addition of anionic surfactants such as sodium dodecyl sulfate (SDS) also effects the triple helical structure of gelatin in aqueous solution. SDS associates with gelatin through hydrophobic interactions involving the hydrocarbon tail, and through ionic interactions between the negatively charged headgroup of SDS and positively charged side groups on the gelatin molecule. It can thus be hypothesised that alteration of gelatin structure by changes in temperature and pH of the solution would effect the overall response of the protein-surfactant complex to increasing concentrations of the non-solvent ethanol. The objective of this work was to determine the effect of increasing SDS concentration and temperature change on the response of B225 gelatin to the non-solvent ethanol at pH’s below and above the IEP of B225 gelatin, by monitoring the phase behaviour of gelatin-SDS solutions in mixtures of water and ethanol, using turbidity measurements.