Dilatational rheology-property relationships of β-lactoglobulin /high methoxyl pectin mixtures in aqueous foams

Interface rheology and macroscopic properties of aqueous β-lactoglobulin (BLG)/High methoxyl pectin (HMP) mixtures at different concentrations of pectin by using dynamic foam analyzer and their molecular properties interfaces as their major structural element were investigated. HMP decreased surface tension to some extend and along with BLG showed unique air-water interface and foam stability. BLG at 15 μM was mixed with HMP at two regimes of concentrations, low and high. The surface tension was decreased in the low regime of HMP and then reached a plateau in the high regime. The maximum surface pressure was obtained at 150 μM of pectin (ratio 1:10 protein to polysaccharide). The CMC, the surface excess (Г), and the molecular area (A) of HMP were ∼150 μM, 2.76 μmol/m² and 0.60, respectively. Similarly, the highest diffusion rate was achieved at 150 μM HMP. The diffusion rate (K_diff) penetration rate (K_p), and rearrangement rate (K_r) of BLG/HMP were increased as the pectin concentration was increased. There was a reverse relation between the γ and the E′ of the film layer at the interface. Consequently, the lowest γ and the highest dilatational elasticity were achieved at ∼150 μM. BLG/HMP mixtures revealed a synergistic effect at the air-water interface and in the bulk solution can favorably influence foam stability. There was a positive relationship between the surface pressure, foam rheology and foam stability which can be useful in the foam systems developed by BLG and pectin. The foam stability confirmed that BLG/HMP can stabilize air-water interface due to the coacervation at the interface which improve the foam stability.