Materials

MNEI, Mut3 and Mut9 were obtained as previously described (Leone et al., 2016; Delfi et al., 2021), while Thaumatin was purchased from Sigma (Sigma-Aldrich, United States). Sucrose and sucralose were purchased from the markets. Protein concentration was assessed by UV absorbance at 280 nm using an extinction coefficient (at 0.1%) of 1.41 for MNEI and Mut9, 1.29 for Mut3, and 1.33 for Thaumatin. The water analyzed were HiPerSolv CHROMANORM HPLC grade (VWR), henceforth synthetically indicated as “HPLC”, and commercial mineral waters (Sant’Anna, Rocchetta, and Lieve), selected based on the mineral residue amounts, conductivity, and pH, as indicated in Supplementary Table 1.