# Encapsulated Probiotics: Potential Techniques and Coating Materials for Non-Dairy Food Applications
## 3 Probiotic Encapsulation Techniques
### Drying Method
#### 3.4.4 Fluidized Bed Drying  
Fluidized bed drying, or fluidized bed coating, is a modified spray-drying method that involves intensive, simultaneous heat and mass transfers between solid particles in a suspension (produces capsules with sizes of 5-5000 \(\upmu\)m). In the fluidized bed drying process, dried pre-encapsulated probiotics are first suspended in a hot air flow. Subsequently, the surfaces of the particles are fluidized with the biopolymer solution. The biopolymer coating is then solidified into a homogeneous layer surrounded by the pre-encapsulated probiotics [44,50]. In the fluidized bed drying process, the aqueous medium is dried in a uniform airflow, and the dried particles are suspended in the heated air. Hence, the particles are evenly dried with much less agglomeration and are uniformly coated. Compared with spray and freeze-drying processes, fluidized bed drying requires less energy consumption, and therefore, it is comparatively economical. Compared to other techniques, a lower drying temperature (ranges from ambient temperature to 120 \({}^{\circ}\)C) can be set and used in fluidized bed drying. Hence, it can preserve heat-sensitive probiotics. For example, [PERSON] et al. [65] proved that the viability of _Bifidobacterium_ sp. was retained for more than 2 years, with a concentration exceeding 5 log CFU/g, as well as resistance to acid and complete enteric-targeted release, through the fluidized bed drying technique. The fluidized bed drying technique is ideal for food industries as it is easy to scale up and can be prepared in large batch volumes and high throughputs. Fluidized bed drying can provide multi-coating layers. Thus, it can contribute to a variety of functional properties. Nevertheless, this technique is time-consuming (\(\sim\)2 h), likely to kill the probiotics, andit is not easy to master. Therefore, probiotics should be encapsulated before drying in a fluidized bed dryer [43; 44; 62; 66].  
Fluidized bed drying techniques have been successfully used by [PERSON] et al. [11], [PERSON] et al. [32], and [PERSON] and [PERSON] [26] to preserve the viability of probiotics in non-dairy food matrices. [PERSON] et al. [11] dried and coated apple cubes with a mixture containing hydroxyethyl cellulose and polyethylene glycol containing _B. coagulans_ using the fluidized bed drying technique. The viability of probiotics in the dried apple snacks was well preserved during the storage period. The fluidized bed drying technique has also been used by [PERSON] et al. [32] to develop probiotic bread. The double-layered (first layer: microcrystalline cellulose powder and alginate or xanthan gum; second layer: gellan or chitosan) microcapsules produced through the fluidized bed drying technique had higher heat resistance and could protect the encapsulated probiotics (_L. Sporogenes_) under baking conditions. In the study of [PERSON] and [PERSON] [26], carrot tablets containing _L. plantarum_ TISTR 2075 were produced using a fluidized bed drying technique employing gelatin. The finding indicated that the _L. plantarum_ TISTR 2075 encapsulated in carrot tablets (survivability: 77.68-87.30%) had higher tolerance against heat digestion treatments than free cells (39.52%).