Sentence:  A number of investigators have shown that the starting composition of a parent oil can have a major influence on its predisposittion to form stable water-in-oil emulsions (<WSD>mousse</WSD>). For example, the presence of natural surfactants in the wax, resin, and asphaltene fractions of oils has been positively correlated with the tendency to form <WSD>mousse</WSD>. 
Meaning of the word marked with <WSD> tags:  A stable emulsion of water and oil that is created by wave action churning the water where an oil spill occurs.