Binary mixture of monostearin‐distearin monolayers at the air–water interface

Abstract

The study of mixed films has become of considerable interest both fiom theoretical and practical points of view. The 7~ -A isotherms of monostearin-distearin (about 50% 1,3-and 50% I,2-isomers) mixed films spread on water as a function of emulsifier ratio and temperature were studied in an automated Langmuir-type film balance. M e n molecules of both emulsifiers are spread on the air-water interface they are packed more closely together than when either emulsifier is present alone, and they enter into some form of association. This association can be demonstrated by surface pressure-area isotherms and by thermodynamic studies. The characteristics of the mixed films, their elasticity and miscibility, which are of interest in emulsion or foam stability, are discussed. A molecular model established can explain the interactions between film and subphase molecules and their relationships with variables of the process (pressure and temperature). This model fits the calculated thermodynamic parameters. will any of the single-component emulsifiers (Kako and Kondo, 1979). This stability is improved still further by incorporating protein in both mono-and diglycerides Sherman, 1983,1984;Rahman and Sherman, 1982;Reeve and Sherman, 1988). Interactions between proteins and lipids have been reported for model food systems in solutions or in emulsions (Coke et al.

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 −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, 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 , due to the fact that the collapse pressure of mixed monolayers is similar to that of the pure monoglyceride monolayer (Figures −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…”