Jmr. Patino et al., Whey protein isolate-monoglyceride mixed monolayers at the air-water interface. Structure, morphology, and interactions, LANGMUIR, 17(24), 2001, pp. 7545-7553
The surface pressure (pi)-area (A) isotherms and Brewster angle microscopy
(BAM) of monoglyceride and whey protein isolate (WPI) mixed films spread on
buffered water at pH 5 and 7 and at 20 degreesC were determined as a funct
ion of the mass fraction (X) of monoglyceride (monopalmitin or monoolein) i
n the mixture. From the X and pi -dependence on excess area, free energy, c
ollapse pressure, BAM images, and the evolution with pi of the relative ref
lectivity (I) of BAM images, it was deduced that the structural characteris
tics, miscibility, and morphology of monoglyceride-WPI mixed films are very
dependent on surface pressure and monolayer composition. The monolayer was
more expanded as the monoglyceride concentration in the mixture was increa
sed. Over the overall range of existence of the mixed film, the monolayer p
resents some heterogeneities. At higher T, after the WPI collapse, characte
ristic squeezing-out phenomena were observed. At the monoglyceride monolaye
r collapse, the mixed film was practically dominated by the presence of mon
oglyceride. However, some degree of interactions exists between monoglyceri
de and WPI in the mixed film, and these interactions are more pronounced as
the monolayer is compressed at the highest surface pressures.