Phase Separation Induced by Conformational Ordering of Gelatin in Gelatin/Maltodextrin Mixtures

Abstract

Mixtures of gelatin and maltodextrin in aqueous solution have been quenched to temperatures at which they are initially miscible but where gelatin ordering is initiated. In many cases phase separation was observed to occur after a significant time delay, and the dependence of these delays on quench temperature and biopolymer concentration has been studied in detail using turbidity measurements and confocal laser scanning microscopy (CLSM). Furthermore, by observing the optical rotation (OR) and turbidity of the system simultaneously, the gelatin helix content and the time delay before the onset of phase separation were monitored concurrently. The observed delay times were found to correspond to the time taken for the development of a certain degree of gelatin ordering, which drives the separation process. A further consequence of gelatin ordering is the viscosifying of the solution and, at sufficient concentrations, the formation of a gel. Therefore, rheological measurements have been used in addition to turbidity measurements and CLSM in order to monitor further the structural development of the systems. A comparison of the data obtained from these techniques shows that while the development of a certain elasticity will trap the system morphology, this elasticity is not directly related to that found at the gel point. At low maltodextrin concentrations, where phase separation was not detected by turbidity, transmission electron microscopy (TEM) has been used to examine the microstructure on a smaller length scale.

Phase Behavior of the ι-Carrageenan/Maltodextrin/Water System at Different Potassium Chloride Concentrations and Temperatures

“…In the present case, K + could bind to the ι-carrageenan helix and promote helix aggregation through reduction of the charge density, resulting in gelation 22,34 . While mixtures were in the liquid state at 80°C and higher, suggesting that KCl concentrations were not high enough to give rise to ι-carrageenan gelation, the added KCl could have promoted the coil → helix transition to a greater extent, altering both polymer rigidity and increasing molecular weight through association 35 . These two effects result in a reduced entropy penalty for the formation of two phases and can add additional forces for phase separation.…”

“…Segregative phase separation is driven by the Flory-Huggins interactions of polymer-polymer and polymer-solvent that are much more temperature dependent 35 , whereas associative phase separation usually originates from the relatively temperature-insensitive electrostatic interaction between polymers. Enhanced biopolymer compatibility at higher temperature is understandable, since the repulsive interactions 1 A "steeper" tie-line in the case of the pseudo-binary phase diagrams presented here actually corresponds to a less steep or more horizontal tie line in the true ternary phase diagram.…”

Hydrocolloid Gums – Their Role and Interactions in Foods

“…Kasapis et al (1999) and Lundin et al (1999) have shown that this is the case for mixtures of the same polymer type such as for mixtures of high and low acyl gellan and iota-and kappa-carrageenan, respectively. Loren et al (2001) followed quenched mixtures of gelatin and maltodextrin and found that phase separation was initiated when a certain amount of gelatin helices had been formed during ordering. Gelation of gelatin in the presence of a range of hydrocolloids has been shown to drive segregation, leading to flocks or gel particles depending on the type of hydrocolloid (Harrington and Morris, 2009).…”

Synchrotron Based FTIR Spectromicroscopy of Biopolymer Blends Undergoing Phase Separation

“…Thus, it can be deduced that the polymers in the mixture are mostly incompatible in the experimental conditions, as already demonstrated by other methods (see Loren et al references therein). 27 The intensity distribution maps for gelatin, maltodextrin, and water are shown for sample RT in Fig. 3.…”

“…[13][14][15][24][25][26][27] The ternary system is homogeneous only in the diluted regime and at high temperatures, as critical temperatures and concentrations are correlated with each other. The thermodynamics of the mixture can be properly described in terms of the FloryHuggins interaction parameters χ, predicting phase separa- Fig.…”