Potato proteins have been shown to be suitable alternatives for animal proteins in food foam formulations but their ability to form and stabilize foam is mechanistically ill-understood. The present study aimed to better understand the foaming properties of a protein fraction isolated from potato trimmings, a by-product from the potato industry. This was achieved by comparing the properties of these in-house isolated proteins to those of commercial and highly purified potato proteins. Protein isolates (53.8 ± 4.7 g/100 g dry weight) were produced from trimmings by alkaline solubilization (pH 9.0) and isoelectric precipitation (pH 4.0). The foaming properties of the in-house isolate at pH 3.0 and 7.0 were better than those of a blend of commercial potato proteins with similar relative amounts of patatin and protease inhibitors as the in-house isolate. Notably, this was the case despite the fact that more proteins were insoluble in the in-house isolate than in the commercial potato protein suspensions. Patatin and protease inhibitors were further shown to both contribute considerably to the formation and stabilization of foams. Interestingly, a beneficial effect on foam stability was found when patatin and protease inhibitors of various colloidal sizes were present. Additionally, impurities in the in-house isolates likely contributed to their superior foaming properties. In conclusion, a protein-rich fraction with good foaming properties can be recovered from potato trimmings. Mechanistic insights were gained into the foaming properties of potato protein (mixtures). This research also highlighted the importance of assessing protein colloidal state when investigating plant protein structure-function relationships.