The objective of this study was to evaluate how the degree of polymerization (DP) of the inulin affects the physical properties of the whey beverage stability. Nine formulations were manufactured using full-fat pasteurized and homogenized milk (30 g 100 g⁻¹), whey powder (6 g 100 g⁻¹), soursop pulp (15 g 100 g⁻¹), sugar (8 g 100 g⁻¹), inulin (6 g 100 g⁻¹) of 2 different DP, GR (DP ≥10) or HP (DP ≥23), and 2 different stabilizers, gellan gum (GG) (0.05 g 100 g⁻¹) or gum acacia (GA) (0.5 g 100 g⁻¹). The ingredients were homogenized with a multiple phase disperser (10 min). The phase separation was evaluated during storage of 24, 48 and 72 h at 6 ± 2°C, using separation index (SI) and light backscatter scan analyzer. Rheological properties were evaluated immediately after its processing. Mean pH values was 5.4 ± 0.1 with no difference among the samples (P > 0.05). It was observed a slight increase of SI through storage time (P > 0.05). The addition of HP inulin was effective to decrease the SI beverage value when compared with control at 72 h (14%, P < 0.05), but GR was not effective (43%, P > 0.05). However, the GG stabilizer was effective to reduce the SI from GR samples (15%). Using the light backscatter scan analyzer it was possible to make backscattering profiles until 3 d of storage, thus, the visual examination of graphics showed longer stability of the HP-GG formulation with increasing of backscattering during the storage time. All samples presented a pseudo plastic flow behavior (P > 0.05), being the consistency index (k) influenced by different formulations, but the addition of only inulin was not significant (P > 0.05). However, the association of inulin and GG greatly influenced the consistency index (P < 0.05). Regards the viscosity values, it was noted an effect of inulin and stabilizer content (P < 0.05), but different DP provided similar results. Overall, the inulin had a great effect on physical stability, but without a stabilizer, a higher DP was more effective and the influence of DP reduced when GG was used.