A Turbidimetric Study of Phase Separating Biopolymer Mixtures during Thermal Ramping

Abstract

A method for particle sizing using a commercial spectrophotometer is presented, based on a Rayleigh-Gans-Debye treatment of the wavelength dependence of turbidity. The finite acceptance angle of the spectrophotometer has been taken into account and shown to be potentially advantageous. The method has been used to monitor the kinetics of droplet growth in phase separating biopolymer mixtures of gelatin and maltodextrin, and predicted droplet sizes have been compared with data obtained from confocal laser scanning microscopy. Furthermore, the temperature dependence of the turbidity data is used to construct a model of the phase behavior of the biopolymer mixture. For systems demixing between 60 and 30 °C, the driving force for phase separation is solely governed by the temperature-dependence of the Flory-Huggins interaction parameters. Below 30 °C the gelatin ordering triggers additional driving forces for phase separation and subsequently leads to the formation of a gel network that traps the system microstructure.

Elastic Networks of Protein Particles

“…Gelation during phase separation was used to produce protein particles, because this technique is known as a suitable method to produce spherical protein particles. 22,23,[29][30][31][32][33][34] However, this technique has some limitations because it requires the use of a polysaccharide to induce phase separation. We washed the protein particle suspension to remove most of the polysaccharide present in the system.…”

“…22,23,[29][30][31][32][33][34] A 10% (w/w) gelatin stock solution was prepared by stirring a gelatin solution for 2 h at 50°C. A 10% (w/w) stock solution of dextran was prepared by stirring for 1 h at 80°C.…”

“…20,21 The rate and onset of phase separation and gelation are important characteristics for the morphology of the protein structure produced, 22,23 and are critically dependent on the concentration, temperature and molar mass of the continuous phase. [24][25][26][27][28] Creation of protein particles is possible for a limited number of biopolymers using specific process conditions.…”

Synchrotron Based FTIR Spectromicroscopy of Biopolymer Blends Undergoing Phase Separation

“…Under these circumstances, small droplets of a few microns are generated, a condition known as "kinetically trapped gels". [13][14][15] Therefore, although demixing is present, the spots are smaller in size than in sample HT, and their dimension can even be inferior to the resolution of the technique. This is indirectly confirmed also by the fact that the extremes in the scale of the ratio change only slightly, i.e., there is a difference of about 20% from maximum to minimum, showing a more uniform distribution on the scale of the resolution (4-6 μm).…”

“…[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.…”