Infant formulas (IFs) can be defined as substitutes for human milk, which are mostly based on cow milk proteins. For sustainability reasons, alternative to animal proteins in food have to be considered. Plant proteins offer interesting nutritional and functional benefits for the development of innovative IFs. However, the behaviour of these proteins during processing and storage must ensure the physical stability and ability to reconstitution of IF powders, and that needs to be tested. This work aimed to study how a partial substitution of dairy proteins by plant proteins may influence the functional properties of 1st age IFs. Three IFs were developed at a semiindustrial scale using two different processing routes. The IFs composition was identical, except that 50% of the proteins were whey proteins in the “reference IF” (RIF), and pea or faba bean proteins in the “plant IFs” (PIF and FIF, respectively). After reconstitution, the three IFs result in similar stable emulsions with equivalent free fat release. In comparison to RIF, PIF and FIF were difficult to disperse, conducting to remaining insoluble particles. Thus, the protein source greatly influences IFs properties, and process parameters need to be adapted for each formulation to meet IFs quality criteria.