Galactomannans are polysaccharides commercially used in foods as gelling agents, thickeners, and stabilizers. In this study, a galactomannan partially hydrolyzed fromAdenanthera pavoninaseeds was used as stabilizer, fat substitute, and source of dietary fibers in amoussemilk dessert. First, characterizations of intact (GM) and partially hydrolyzed (GMPH) galactomannan fromA. pavoninawere made. Through Rotational Central Compound Design (RCCD) and the response surface methodology, we evaluated creaming index, lipid content, moisture content, and texture of themousses. The formulation F7 (1.75% of GMPH and 4.92% of fat) was chosen among the developed formulations, and it was characterized by low moisture content (44.13%), low lipid content (6.67%), low firmness (2.10 N), and high percentage of dietary fiber (4.21%). This formulation was compared with a traditional formulation of lemonmousse(FT) and with another formulation with the same fat percentage as the chosen formulation without GMPH (F7L). The three formulation were characterized physicochemically and microbiologically, and sensorial acceptance tests were performed. The results indicated that no structural modifications were found in the galactomannan after its partial hydrolysis.and good sensory acceptance when compared to FT. The lemonmoussesproduced met sanitary specifications, remaining stable for 21 days of storage. We concluded that the use of GMPH fromAdenanthera pavoninaseeds in lemonmoussesproved to be a stable, light dessert alternative and a potential source of dietary fiber.