The effect of calcium on the foam behaviour of aqueous sodium alkyl benzene sulphonate solutions. 2. In the Presence of triglyceride-based antifoam mixtures

Abstract

Here we have sought to establish the likely key ingredients which determine the antifoam behaviour of model sebum together with key specific aspects of their mode of action. Since the overall composition of sebum is dominated by unsaturated triglycerides we selected triolein as the oil. Tristearin and stearic acid were selected as particulate components since both are only sparingly soluble in triolein and are likely to replicate the absence of strong dependence upon changes in pH or [Ca2+] found with sebum. Triolein/tristearin mixtures were, under most circumstances, at least as effective as the model sebum but totally unaffected by changes in [Ca2+] and pH. However triolein/stearic acid mixtuures replicated the weak dependence upon [Ca2+] of model sebum and pH but were less effective. The ineffectiveness of the former appeared to concern the relatively large size of stearic acid particles crystalizing from a melt in triolein – at least an order of magnitude larger than the particle sizes of tristearin prepared in a similar manner, showing a tendency to aggregate and form large, ineffective, triolein/stearic acid agglomerates. The large particle size of stearic acid particles also leads to a high probability of formation of ineffective particle-free drops upon dispersal in solution.