Mixed monolayers of acylglycerols on sugar aqueous solutions

Abstract

Structural characteristics of mono-and distearin mixed monolayers spread on aqueous solutions containing sugar (glucose or sucrose) at 0.5 mol/L were studied as a function of temperature and integacial and subphase compositions. The compression isotherms were obtained using an automated Langmuir-type film balance over a temperature range of 10 to 40°C. The results show an expansion in the structure of the mixed monolayer with sugar in subphase. Nonideal mixing of the component at interface was observed with positive deviation from the additivity rule. This fact is indicative of the presence of repulsive interactions between the two lipids on sugar aqueous solutions. The mixed monolayers with a monostearin molar fraction less than 0.8 are stable from a thermodynamic point of uiew. Mixed monolayer stability depends on monolayer composition, temperature, and surface pressure with diflerent order of magnitude.

Whey Protein Isolate−Monoglyceride Mixed Monolayers at the Air−Water Interface. Structure, Morphology, and Interactions

“…The structural characteristics and morphology of monoglyceride-WPI mixed films are dependent on surface pressure, monolayer composition, and, to a minor extent, on the aqueous phase pH. From the π-A isotherm of mixed monolayers (Figures 1-3), including the application of the additivity rule on miscibility and the quantification of interactions between monolayer components by the excess free energy (data not shown) and according to results for other systems, 31 it has been shown that, at a macroscopic level, monoglyceride-WPI mixed monolayers form a mixed monolayer at the air-water interface with few interactions between film-forming components, at surface pressures lower than that for the WPI collapse (π ≈ 31 mN/m). At the highest surface pressures, at the collapse point of the mixed film, immiscibility between monolayer-forming components is deduced 32,33 due to the fact that the collapse pressure of mixed monolayers is similar to that of the pure monoglyceride monolayer (Figures 1-3).…”

Structure, Miscibility, and Rheological Characteristics of β-Casein−Monoglyceride Mixed Films at the Air−Water Interface

“…In addition, in many emulsifier applications, mixtures of different emulsifiers (mainly polar lipids and proteins) often exhibit properties superior to those of the individual emulsifier alone due to synergistic interactions between emulsifier molecules. In previous works with mono-and diglycerides (8)(9)(10) or mixtures of monoglycerides and milk proteins (11,12) we observed that when molecules of both emulsifiers were spread at the air-water interface they were more expanded or packed more closely together than when either emulsifier was present alone, indicating some form of association. Interactions between molecules of emulsifiers could affect not only film structure and morphology (13)(14)(15) but also the relaxation phenomena in mixed films (16,17).…”

“…The interactions between components in mixed monolayers can be studied from the point of view of miscibility between components in the mixed monolayer ( , ). In Figure we show the molecular area ( A ) and the mean area ( A i ) calculated according to the additivity rule (), A i = A 1 X 1 + A 2 X 2 , where A 1 and A 2 are the molecular areas of pure components and X 1 and X 2 are the mass fractions of pure components in the mixed monolayer.…”

“…The interactions between components in mixed monolayers can be studied from the point of view of miscibility between components in the mixed monolayer (8,10). In Figure 3 we show the molecular area (A) and the mean area (A i ) calculated according to the additivity rule (30)…”

Static and Dynamic Properties of a Whey Protein Isolate and Monoglyceride Mixed Films at the Air−Water Interface

“…The interactions between components in mixed monolayers can be studied from the point of view of miscibility between components on the mixed monolayer. , In Figures and we show the molecular area ( A ), the mean area ( A i )calculated according to the additivity rule in eq 7and the excess free energycalculated according to the equation derived by Goodrich and Pagano and Gershfel, eq 8for WPI−monopalmitin (Figure ) and WPI−monoolein (Figure ) mixed films. The continuous lines in Figures and correspond to an immiscible monolayer…”