*4.3.3.1 Synbiotic formulations*

It is recognized that combining prebiotics and probiotics together in synbiotic powder formulations may boost the viability of probiotic strains [89]. Prebiotics are substrates that serve as probiotic nutrients, and mainly consist of carbohydrate compounds such as inulin, oligosaccharides (e.g. GOS, XOS), and fructooligosaccharides [92]. Thus, the wettability of their mixture is an important indicator for ensuring the synbiotic performance, either in synergism or in complementary [93], dispersibility in a fluid, and stability during storage.

### *4.3.3.2 Encapsulation and coating processes*

Encapsulation and coating processes are often used for protecting the probiotics and synbiotics against environmental stress conditions in order to maintain a high level of viability, stability, and performance [94]. It uses various food-grade

### *Wettability of Probiotic Powders: Fundamentals, Methodologies, and Applications DOI: http://dx.doi.org/10.5772/intechopen.106403*

biopolymers, mostly derived from polysaccharides (e.g. gum Arabic, alginate, chitosan, resistant starch, etc.) and proteins (e.g. milk and soy proteins), and different technologies, including the bulk or microscale matrix encapsulation systems and the individual cell encapsulation via nanocoatings [95]. The first method is based on the immobilization of probiotics into a gel matrix (e.g. hydrogel systems) whereas the second one is based on the formation of nanofilms around individual probiotic cells (e.g. cytoprotective approaches based on silica, graphene, metal-polyphenol nanoshells, etc.).

In both cases, the wettability of probiotic powders before and after encapsulation or coating processes appears important for operating convenient choices of coating agents and processes but also for the final product performance. In fact, the microbial probiotic surface properties such as hydrophobicity and polarity as well as the permeability/porosity of the powder have an impact on the compatibility and interactions with the coating or encapsulation materials for ensuring an appropriate stability and permeability of the formulated products. Based on several investigations, the survival rate of probiotic strains may vary between 68 and 94% during the storage and digestion, depending on the coating or encapsulating materials and methodologies used [94]. Nevertheless, such protective processes are not necessary for the sporeforming bacteria such as *Bacillus* strains which convert from vegetative into resistant spore forms by naturally producing a protective shell under harsh conditions, including high temperature, pressure, and acidity, as well as heat, desiccation, radiation, and oxidation conditions [95]. It might also be the case of Lactobacillus strains through self-encapsulation mechanisms by producing a thicker layer of EPS, when the environmental factors and stress conditions of fermentation are modified [96].
