Gaining insight on spray drying behavior of foods via single droplet drying analyses

Abstract

A continuous challenge for spray drying operations is the optimal control of product quality despite the complex process removal of water and particle formation. In general, high product functionality (e.g. in terms of reconstitution behavior, high enzyme activity or appropriate living probiotic bacteria) is key to the success of spray-dried powders. In this article, we review scientific studies that employ single droplet drying approaches to unravel underlying phenomena of spray drying process. Moreover, we identify scientific challenges to advance single droplet drying studies and thus contribute to development of mechanism-based guidelines for spray drying of functional food powders.

Unraveling Particle Formation: From Single Droplet Drying to Spray Drying and Electrospraying

“…In case of contact levitation, the droplet is suspended on a filament, while in the case of non-contact levitation methods, the droplet floats in the air due to an acoustic field or an air stream [ 1 ]. Several excellent reviews discuss the physical mechanisms involved in these techniques and the different types of information that can be gathered using them [ 1 , 14 , 15 , 16 , 17 ]. In Table 1 , an overview of their principles, (dis)advantages, and similarity to pharmaceutical applications can be found.…”

“…Therefrom, a droplet drying curve can be developed [ 24 ]. Alternatively, continuous measurement of the RH of the moisture content by a dew point hygrometer also enables evaluation of the drying rate [ 17 ]. Next to the drying rate itself, an infrared thermometer and a video camera can be used to measure the droplet temperature and its morphological development, respectively [ 14 ].…”

“…Sedelmayer et al carried out acoustic levitation droplet drying experiments with (NH 4 ) 2 SO 4 and mannitol and stated that the surface roughness has a linear dependence on the solute fraction, namely the higher the concentration of the dissolved solid, the rougher the surface [ 58 , 59 ]. In the research of Schuytser et al, in contrast, smoother surfaces were obtained for higher concentrations [ 17 ].…”

Role of critical reviews in encouraging appropriate R&D

“…During the last two years (2018-2019), this journal has published 14 review papers covering a wide range of themes and applications in a number of industrial sectors, ranging from agricultural products, [1,2] food, [3] to pharmaceuticals, [4,5] and microorganisms [6] . Both scientific approaches [5,7,8] and industrial applications [9] are covered to meet the needs of industry as well as academia.…”

In situ Raman composition profiling in drying droplets

“…The prediction of particles structure (physical spatial location of components within the particles) and morphologies is a major scientific challenge regarding the spray drying process [14]. The drying process involves simultaneous heat and mass transfer, phase transition, flow and mechanical instability (during solid formation).…”