AbstractThe influence of acetylation on surface adsorption and emulsifying properties of faba beans protein isolates (FBPI) was studied. Generally, acetylation improved the interfacial activity of FBPI. The plateau value of the Gibbs' adsorption isotherms measured with the Wilhelmy‐plate was between 22.97 and 24.22 mN/m. The critical association concentration (CAC), i.e. the inflection point of the adsorption isotherms, was shifted from 2.06. 10−5to 5.35. 10−7g/ml with progressive acetylation. The dependence of the CAC on the degree of acetylation was found to be significant. For FBPI stabilized n‐decane/water emulsions with varying volume fraction of oil (ϕ) the emulsifying activity index increased from 166 to 593 m2/g whereas the droplet size decreased from 7.79 to 3.4 μm with acetylation. The correlation between emulsifying activity of FBPI and both degree of acetylation and adsorption behaviour was only significant for emulsions w