Dianawati, Dianawati (2014) Survival of encapsulated probiotic bacteria during storage at low water activity at ambient temperature. PhD thesis, Victoria University.

Abstract

Probiotics are defined by FAO/WHO (2001) as microorganisms that improve the healthiness of the host when available in sufficient number in the human intestinal tract. Health benefits of probiotic bacteria are correlated with the number of viable bacteria reaching the host and the recommended bacterial population required is ≥107 CFU/g. Besides during processing and storage, probiotic bacteria are required to survive during transit in gastrointestinal tract with very low pH (1.8 – 2.0), in bile juice and pancreatin before beneficial effects are realized in the lower small intestine and colon. Microencapsulation is effective in ensuring bacterial viability which is influenced by the type of encapsulating materials, the methods used for encapsulation and storage thereafter for a given bacterium. The use of microencapsulating materials is to entrap or immobilize probiotic bacteria within microcapsule and to protect the bacteria during the drying process, which is the last stage of microencapsulation. The objectives of this thesis were to study the effect of different types of microencapsulants (alginate or casein-based formulations), and drying methods (freeze and spray drying) on survival of probiotic bacteria for 10 weeks of storage at 25oC (ambient temperature) at low water activities (aw). Three probiotic bacteria (Bifidobacterium animalis ssp. lactis Bb12, Bifidobacterium longum and Lactobacillus acidophilus) and one strain of most sensitive lactic acid bacteria (L. lactis ssp. cremoris) to acid and bile environment were encapsulated and selected functional properties, such as survival, acid and bile tolerance, surface hydrophobicity, and retaining of some of the enzyme activities were investigated. The protective mechanism of microencapsulation was studied by determinations of microstructures using Environment Scanning Electron Microscopy (ESEM), interactions with cellular components by Fourier Transform Infrared Spectroscopy (FTIR), and glass transition temperature (Tg) measurements by Differential Scanning Calorimetry (DSC).

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