טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDavid Semyonov
SubjectDry Microencapsulation and Enteric Coating of Probiotic
Bacteria
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Dr. Shimoni Eyal
Full Thesis textFull thesis text - English Version


Abstract

The central goal of this study was to develop a dry form of microencapsulated probiotics, an appropriate food-grade enteric coating, and the appropriate manufacturing technology. This will ensure their stability during processing, storage, and most importantly during their passage through the GI tract.

Three techniques were examined for the production of microencapsulated viable probiotic core: freeze drying, ultrasonic vacuum spray drying (UVSD), and spray coating processes. Spray coating process was used for coating the capsules produced by one of the three encapsulation processes. In order to create a matrix that will provide optimal protection during probiotic bacteria drying, different combinations of maltodextrins and disaccharide were used. Ethylcellulose and resistant starch (RS) were used as enteric coatings, along with wax (HVO).

Dry microencapsulation of L. paracasei was carried out successfully by all three technologies. Along with drying temperature, matrix formulation had a significant influence on probiotic survival during the encapsulation processes. For example, less than 1% of L. paracasei survived the freeze drying process without protection matrix. Disaccharide concentration in the matrix formulation was a major parameter affecting probiotic survival, and the optimal combinations were maltodextrin-disaccharide [1:1] and [1:2]. The highest survival was achieved by bulk freeze drying (BFD) (85%). However, primal disadvantage of BFD is the bulk form of the dry product that have to be micronized, process that causes decrease of the dried cells viability. Spray freezing - freeze drying (SF-FD) process was therefore used to produce spherical particles (≥400 µm) with over 60% survival. UVSD process provided dry probiotic powder (25-40 µm) with over 70% survival. Spray coating process produced probiotic capsules (200-250 µm) with lower final viability (<40%).

Storage conditions such as temperature, oxygen level humidity, and matrix formulation, influenced probiotic shelf life. Combination of low storage temperature, low oxygen level and the appropriate disaccharide provided optimal storage stability. Wax coating increased probiotic storage stability in humid environment. On the other hand, RS coating, in addition to its thermo protective role, can function as an oxygen barrier. Wax-ethylcellulose bi-layer coating provided good protection in acid environment. Probiotic survival under these conditions was 2000 fold higher than un-coated bacteria. It can therefore be concluded that successful microencapsulation of probiotic bacteria in dry matrix followed by enteric coating, for storage stability and potential acid stability, was demonstrated.