Foam Structure Preservation during Microwave-Assisted Vacuum Drying: Significance of Interfacial and Dielectric Properties of the Bulk Phase of Foams from Polysorbate 80-Maltodextrin Dispersions.

Peter Kubbutat,Jannika Dombrowski,Ulrich Kulozik

doi:10.3390/foods10061163

Peter Kubbutat, Jannika Dombrowski + Show 1 more

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https://doi.org/10.3390/foods10061163

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Abstract

This study aimed at examining the cause of differences in the structure preservation of polysorbate 80–maltodextrin foams during microwave-assisted vacuum drying (MWVD) versus conventional vacuum drying (CVD). Aqueous dispersions of 3% polysorbate 80 and 0–40% maltodextrin were characterized for their dielectric and interfacial properties, and results were related to their drying performance in a foamed state. Surface tension and surface dilatational properties as well as dielectric properties clearly responded to the variation in the maltodextrin content. Likewise, the foam structure preservation during CVD was linked to the maltodextrin concentration. Regarding MWVD, however, foams collapsed at all conditions tested. Nevertheless, if the structure during MWVD remained stable, the drying time was significantly reduced. Eventually, this finding could be linked to the dielectric properties of polysorbate 80 rather than its adsorption kinetics and surface film viscoelasticity as its resonant frequency fell within the working frequency of the microwave drying plant.

Highlights

For the preservation of heat-sensitive biological material, vacuum drying has evolved into a promising alternative to time- and energy-intensive freeze drying
Enzymes [3] or pharmaceutical ingredients [4]), vacuum drying has evolved into a promising alternative to time- and energy-intensive freeze drying
The increased storage stability was linked to product shrinkage during dehydration [7], which, entails a prolongation of the third drying stage

Summary

Introduction

For the preservation of heat-sensitive biological material (e.g., bacterial cultures [1,2]enzymes [3] or pharmaceutical ingredients [4]), vacuum drying has evolved into a promising alternative to time- and energy-intensive freeze drying. Besides advantages in the specific energy demand [5] and drying time [6], vacuum drying was shown to yield products of increased storage stability as compared to freeze drying. Due to the compactness of the dried product structure, its grindability is impaired. In this context, Ambros et al [8] reported that microwave assistance can reduce the vacuum drying time by about 95%. Ambros et al [8] reported that microwave assistance can reduce the vacuum drying time by about 95% This significant effect was related to the volumetric energy input of the microwaves allowing for a high mass transfer over all drying stages. Controlled product aeration (i.e., foaming) prior to microwave-assisted vacuum drying (MWVD) was proposed to tackle the drawback of conventional vacuum drying (CVD) in terms of poor product grindability [9]

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