Studies on microencapsulated probiotic starter cultures for the development of functional beverages

Abstract

newline x newlineABSTRACT newlineProbiotics deteriorate with time as a result of production processes, storage conditions, and digestion, leading to reduced health benefits to consumers. Microencapsulation of microorganisms is an efficient method of increasing probiotic survival by preventing the exposure of the cells to harsh environments throughout the gastrointestinal system until they are released in the colon. Hence, the current study was carried out to identify a suitable novel strain with probiotic properties and its application in the production of various fruit and vegetable probiotic beverages. Thirty bacterial isolates were recognized as lactic acid bacteria based on their phenotypic characteristics and further tested qualitatively for their growth in MRS broth at different pH. Based on preliminary screening, six isolates showed LAB prevalence. Isolates SUMP1, SUMP4 (mango pickle), SUDP6 (dheu pickle), SUBM12 (milk) and SUC21, SUC22 (curd) showed the ability to grow at low pH (1, 2 and 3). These isolates also survived at various concentrations of bile salts (1, 1.5 and 2%) and exhibited good antimicrobial activity. Among six isolates the isolate SUDP6 was identified as Lacticaseibacillus rhamnosus (SUDP6) based on genotypic identification. Further, it showed good acid tolerance at pH 3 and depicted the deconjugation of bile salts, which help their adhesion to epithelial cells and colonization. As a result, it can be concluded that L. rhamnosus (SUDP6) isolated from traditional fermented foods has the potential to be used as a starter culture for the development of probiotic beverages. Further, L. rhamnosus was encapsulated with extrusion and emulsion techniques in a calcium chloride solution. Alginate-probiotic microbeads were coated with xanthan gum, gum acacia, sodium caseinate, chitosan, starch and carrageenan. The alginate+xanthan gum microbeads exhibited the highest encapsulation efficiency (95.13 %) and they were survived under simulated gastric and intestinal juices at pH 3 during 1, 2 and 3 h of incubations at 37°C. The research findings showed a remarkable improvement in the survival rate of microencapsulated probiotics under simulated gastric conditions up to 83.69 % as compared to the free cells. The morphology, size and shape of the microbeads were analyzed using the scanning electron microscope. For the protection of probiotic bacteria under simulated intestinal conditions, alginate microbeads coated with xanthan gum exhibited a survival rate of 87.3%, which was around 38% higher than that of the free cells newlinexi newline(49.4%). Our research findings indicate that alginate+xanthan gum microbeads have a significant potential of delivering probiotic cells to the intestine in large numbers where cells can be released and colonized for consumer s benefit. Different fruit and vegetable juices (apple, orange, beetroot and carrot) were used for the development of probiotic functional beverages. The different treatments (T1, T2, T3, T4 and T5) of ready-to-serve drinks were prepared with different juice concentrations (10, 12, 13, 14, 15%). Among the various ready-to-serve drinks, treatments prepared with 14% juice part (T4) of apple, orange, beetroot, and carrot were found most acceptable based on sensory analysis. The probiotic beverages prepared using microencapsulated L. rhamnosus and free cells stored under refrigerated conditions were found better in physicochemical and sensory characteristics as compared to those stored at ambient conditions. Based on sensory attributes, the probiotic beverages under refrigerated conditions have higher overall acceptability scores along with better color, flavor and taste. Further, the result revealed that the probiotic apple juice beverage was superior with higher sensory scores for all the sensory attributes in comparison to orange, carrot and beetroot beverages. This study showed that microencapsulation of L. rhamnosus with an alginate+xanthan gum coating with emulsion technique is an efficient method for the delivery of viable bacterial cells to the colon and sustaining their viability through simulated gastric and intestinal juices. The primary uses of probiotic microorganisms in fruit and vegetable derived products as well as the characteristics of these food matrices make them an ideal carrier of probiotic bacteria. Keywords: Lactic acid bacteria (LAB), probiotic, microencapsulation, survivability, Lacticaseibacillus rhamnosus, gastrointestinal conditions, microencaspsulated hydrogels