Ph.D. Dissertation:

Effect of inulin and Persian gum as a prebiotic on improvement of growth and survivability of Lactobacillus rhamnosus encapsulation by Whey protein concentration with electrospinning٫ freeze drier and spray drier methods

Probiotics are live microorganisms that when administered in enough amounts offering health benefits on the host. In recent years, we use strains of Lactobacillus and bifidobacterium have been identified in many food products and probiotic supplements and reported for their probiotic potential and application into various types of functional food products. The survivability and dose levels of probiotics during storage conditions and passing through gastrointestinal tract are important parameters for probiotic efficacy. Probiotic bacteria need to be protected against adverse environment and to avoid negative sensory impact on incorporation into foods. Some researchers examined the protecting potential of microencapsulation against environmental stress such as harsh acidic conditions, high temperatures, excessive salinity, and enzyme degradation. Electrospraying, freeze and spray drying were used to microencapsulate Lactobacillus rhamnosus ATCC 7469 in whey protein isolate (WPI), whey protein isolate?+?inulin (WPI?+?IN) or whey protein isolate?+?inulin?+?Persian gum (WPI?+?IN?+?PG) matrixes. Physical properties, survivability, cell injuries and resistance to simulated gastrointestinal condition of L. rhamnosus ATCC 7469 microcapsules were examined. Cell damage evaluation showed that electrospray was more injurious to L. rhamnosus ATCC 7469 cells in comparison with other two methods, also Persian gum had the most protecting effect against cell damaging agents. The viability of encapsulated cells decreased from 10.60-10.97 log cfu/g in the first week to 8.72–10.78 log cfu/g in the last week of storage. Freeze drying and electrospraying showed the lowest and highest loss in cell survival during storage, respectively. Results showed the superiority of freeze-dried microcapsules to prolong L. rhamnosus ATCC 7469 survival when exposed to digestive system conditions.

Keywords: Electrospraying; Freeze-drying; Spray-drying; Cell damage evaluation; Lactobacillus rhamnosus ATCC 7