Thermodynamic and Dynamic Characteristics of Monoglyceride Monolayers Penetrated by β-Casein

In this work, we have analyzed the dynamics of the penetration of β-casein into monoglyceride monolayers (monopalmitin and monoolein) and the structural, dilatational, and topographical characteristics of mixed films formed by monoglyceride penetrated by β-casein. Different complementary experimental techniques [dynamic tensiometry, surface film balance, Brewster angle microscopy (BAM), and surface dilatational rheology] have been used, maintaining the temperature constant at 20 °C and the pH at 7. The surface pressure of the monoglyceride monolayer at the beginning of the penetration process (at π_i^MP and π_i^MO for monopalmitin and monoolein, respectively) was the variable studied. β-Casein can penetrate into a spread monoglyceride monolayer at every surface pressure. The penetration of β-casein into the monoglyceride monolayer with a more condensed structure, at the collapse point of the monoglyceride, is a complex process that is facilitated by monoglyceride molecular loss by collapse and/or desorption. However, the structural, topographical, and dilatational characteristics of the monoglyceride penetrated by β-casein mixed monolayers are essentially dominated by the presence of the monoglyceride (either monopalmitin or monoolein) in the mixed film.