Layla Zaghari; Alireza Bassiri; Somaye Rahimi; Ali Zonousi
Abstract
Intoduction: Probiotic products have been used worldwide in the last decades. They are significantly gaining popularity and their consumption is associated with increasing levels of health-consciousness. Probiotics can be defined as microbial cells that have a beneficial effect on the health and wellbeing ...
Read More
Intoduction: Probiotic products have been used worldwide in the last decades. They are significantly gaining popularity and their consumption is associated with increasing levels of health-consciousness. Probiotics can be defined as microbial cells that have a beneficial effect on the health and wellbeing of the host. In this sense different probiotic products have appeared on the market with different formulations and applications. Bread is the major type of bakery products and a staple food in most part of the world. Despite attempts to develop functional breads containing viable microorganisms, this has not been fully developed yet because of the high temperature during baking process. Viability of probiotic bacteria in the product at the point of consumption is an important consideration for their efficacy, as they have to survive during the processing and shelf life of food. Lactobacillus reuteri which naturally occurs in the human intestine possess probiotic properties with good colonization potential. The main purpose of probiotic encapsulation is to protect cells against an unfavorable environment, include high processing temperatures and storage. The fluid bed encapsulation process consists of spraying a coating solution into a fluidized bed of solid particles. After several cycles of wetting–drying, a continuous film is formed. The main parameters affecting the process are flow-rate and pressure of the spraying liquid, composition and rheology of the coating solution, flow-rate and temperature of the fluidizing air. Double microencapsulation for probiotics by air-suspension fluidized-bed coating is a good alternative method to achieve greater resistance to high temperatures during bread baking. The aim of this study was to evaluate the survival of Lactobacillus reuteri that had been double layered using chitosan, calcium chloride and Arabic gum for microencapsulation and which had been exposed to bread baking conditions.
Materials and Methods: Pure freeze-dried Lactobacillus reuteri PT-1655 were obtained from Persian Type Culture Collection (Tehran, Iran) and were activated by inoculation in the MRS broth at 37°C for 36-48 h. The air-suspension process was performed in a Wurster coater system with a bottom spraying atomizer. In various pretests, the fluidization pressure, the atomization pressure and the spraying rate of the microencapsulation process were varied to examine their influence on process conditions, especially on the particle development. In this study, chitosan, calcium chloride and Arabic gum at concentrations (0.5, 1 and 1.5% w/v), 5% w/v and (1.5, 3 and 6% w/v) were used as second layer in double microencapsulation, respectively. Heat resistance of unencapsulated and double encapsulated microorganisms was determined by placing in an oven which was preheated to 80°C for 15 and 30 minutes. The prepared dough after adding of unencapsulated and double encapsulated bacteria was shaped into loaves of 50 g each, placed in aluminum pans, and baked in a preheated oven at 180°C for 20 min and 70 – 80% relative humidity and then cooled at room temperature. The temperature during baking process was checked by putting a thermocouple at the crumb center. The viability of bacteria at controlled conditions was measured after 1 and 24 h after baking process. Experimental data have been represented as the mean with standard deviation (SD) of different independent determinations. The significance of differences was evaluated by analysis of variance (ANOVA). Differences were considered statistically significant at p
Layla Zaghari; Alireza Bassiri; Somaye Rahimi; Ali Zonousi
Abstract
Intoduction: Probiotics are defined as essential live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. The range of beneficial properties reaches from lowering cholesterol to preventing cancer. The most important probiotic microorganisms belong to the group ...
Read More
Intoduction: Probiotics are defined as essential live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. The range of beneficial properties reaches from lowering cholesterol to preventing cancer. The most important probiotic microorganisms belong to the group of lactic acid bacteria. Lactobacillus reuteri which naturally occurs in the human intestine possess probiotic properties with good colonization potential. The development of probiotic foods presents many challenges, particularly with respect to the stability of the bioactive compounds during processing, storage and passage through acidic gastric environment. Therefore, it is a great challenge to bring the probiotics into a stable form, which guarantees, that the microorganisms reach their target location, the human intestine, in an adequate amount. Microencapsulation helps improve survival probiotic bacteria from environmental stresses. In most studies, probiotic bacteria are entrapped in a gel matrix of natural biological materials such as alginate, or gellan. The core and wall solutions are turned into drops of the desired size by employing an emulsion method. The main problem in the probiotic entrapment approach is that gel bead entrapment technologies generally stabilize the bacteria in liquid products and are difficult to scale up. In order to extend the shelf life of encapsulated probiotics, a glassy state form of the embedding matrix is required. This can be achieved by employing such as air-suspension fluidized-bed coating. In the present research, an air-suspension fluidized-bed technique for generation of core and shell microcapsules containing probiotic Lactobacillus reuteri cells and the efficacy of shellac and sodium alginate at different concentrations on viability of capsules in simulated gastrointestinal conditions was evaluated.
Materials and methods: Pure freeze-dried Lactobacillus reuteri PT-1655 were obtained from Persian Type Culture Collection (Tehran, Iran) and were activated by inoculation in the MRS broth at 37°C for 36-48 h. The air-suspension process was performed in a Wurster coater system with a bottomspraying atomizer. The growth curve of lactobacillus reuteri were determined by measuring the optical density (turbidity) at 600 nm to estimate the time when the growth curve enters a stationary phase in which bacteria develop a general stress resistance and are thus more resistant to various types of stresses. In various pretests the fluidization pressure, the atomization pressure and the spraying rate of the microencapsulation process were varied to examine their influence on process conditions, especially on the particle development. Several different solutions of Lactobacillus reuteri were prepared and evaluated for percentage survival during the coating. The solution containing Lactobacillus reuteri (6–12 g/100 g solution), maltodextrin (4–7 g/100 g solution) and sorbitol (4–7 g/100 g solution) concentrations was spray-coated at three inlet temperatures: 37, 47 and 62°C onto and absorbed by the inert carrier microcrystalline cellulose to produce nonagglomerating dry coated. For the coating processes an aqueous shellac solution at 3 concentrations (16, 17 and 18% (w/v)), containing plasticizers in the ratios of 95 + 5 and an aqueous sodium alginate solution at 3 concentrations (0.5, 1 and 1.5% (w/v)), were used. Simulated gastric juice was prepared fresh daily containing 3.2 mg of pepsin, 1 ml of NaCl solution (0.5%) and acidified with HCl (1.2 M) to pH 1.5 ± 0.5. Tolerance to gastric juice was examined by placing freshly prepared cells in a tube containing sterile simulated gastric juice for 1 h and incubated at 37°C for 2 h. To characterize the morphology of the MCC particles coated with the different matrix formulations, SEM images were taken. Experimental data have been represented as the mean with standard deviation (SD) of different independent determinations. The significance of differences was evaluated by analysis of variance (ANOVA). Differences were considered statistically significant at p
