Phase Segregation in Individually Dried Particles Composed of Biopolymers

Abstract

Mixing of two biopolymers can results in phase separation due to their thermodynamically incompatibility under certain conditions. This phenomenon was first reported when the solution was allowed to equilibrate, but it has later been observed also as a consequence of drying. The challenges of this study were to observe phase segregation by confocal Raman microscopy and LV-SEM on dried film, individually dried particles, and spray dried particles. The influence of the solid content and the phase ratio (composition) of a HPMC/maltodextrin mixture on the localization of the ingredients in the individually dried particles was investigated. We observed that phase segregation of HPMC and maltodextrin is induced by solvent evaporation in film drying, single particle drying, as well as spray drying. The phase ratio is an important parameter that influences the localization of the HPMC-enriched phase and maltodextrin-enriched phase, i.e., to the particle surface, to the core, or in a more or less bicontinuous pattern. The drying time, affected by the solids content, was found to control the level of advancement of the phase segregation.

Comparison of blueberry powder produced via foam‐mat freeze‐drying versus spray‐drying: evaluation of foam and powder properties

“…MDs are commonly used in foods as bulking agents, texture modifiers and fat replacers, and in the formulation of fruit leathers and for the encapsulation of a wide range of products via various drying methods, where the material desired becomes trapped in the glassy MD matrix on drying . It should be noted that when mixtures of low molecular weight sugars and high molecular weight surface‐active compounds such as proteins are spray‐dried, there is a natural tendency for the surface‐active components to end up more concentrated on the outside of the dried particles; that is, components segregate to some extent in the particles . This can affect the rehydration properties of the powders, but it also helps to overcome the stickiness of dried products with high sugar content .…”

Development of a surface tension mediated technique for dry stabilization of mammalian cells

“…Local non-uniformities in moisture content leads to differential molecular mobility in microenvironments which may degrade the entire sample while in storage [ 27 ]. Desiccation processing cells using passive diffusion techniques [ 1 , 11 ] create local non-uniformities in residual moisture contents in the dried product due to several factors including non-uniform surface evaporation [ 28 ], Marangoni flow instabilities [ 29 ], and interface phase separation of the solute [ 30 , 31 ]. The surface tension based desiccation technique described here can be used to create highly desiccated films with very uniform moisture contents ( Fig 2C ).…”

Latest advances in imaging techniques for characterizing soft, multiphasic food materials

“…ESEM images were obtained in low vacuum mode (100 Pa) in order to minimize sample damage and improve micrographs quality. Further applications of ESEM can be found in Nuzzo et al, 2015, where this technique has been coupled with Raman Confocal Microscopy to study the phase separation of cellulose and maltodextrin triggered by water evaporation. The same combination of techniques was also used to evaluate the effect of different drying processes on whole milk particles; moreover, a comparison of using different detectors for visualizing the images is presented in Figure 5 (Nuzzo et al, 2017).…”

“…The focused penetration of Raman microscopes can be exploited to probe the internal structure of solid particles. Powders containing hydroxypropyl methylcellulose (HPMC) and maltodextrin (Nuzzo et al, 2015), whole milk (Nuzzo et al, 2017) and milk serum and lactose (Andersson et al, 2019), produced with different drying techniques were investigated in this fashion. CRM was applied to probe the inner phase separation of the components after controlled evaporation of the aqueous solvent; even in the case of whole milk, all major constituents (lactose, fat and protein) were spatially resolved.…”