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ABSTRACT: Fermentation temperature (34–40 °C), total inoculum level (1%–3%, v/v) and peeled-fruit-to-water ratio (12.5%–37.5%, w/v) were combined to study their effects on the fermentation of banana media by free and Ca-alginate or κ-carrageenan-immobilised Lactobacillus acidophilus. A three-variable and three-level design method, analysed by response surface methodology (RSM), was used. These factors, except peeled-fruit-to-water ratio, were found to be significantly effective on viable cell numbers and 1-kestose (GF2) concentrations. Contour plots were generated using a graphing software package (Surfer Mapping System, Version 5.0; Golden Software Inc., Golden, CO, USA, 1994) based on fitted quadratic regression equations. Optimum conditions for the highest viable cell number and higher GF2 concentration were found to be around 35 °C fermentation temperature, 1.2% inoculum level and 25.0% peeled-fruit-to-water ratio for Ca-alginate immobilised cell fermentation, and around 39 °C fermentation temperature, 1.8% inoculum level and 25.0% peeled-fruit-to-water ratio for κ-carrageenan immobilised cell fermentation. For free cell fermentation, conditions for the highest viable cell number and higher GF2 concentration could not be obtained. The predicted optimum conditions of immobilised cell fermentation and the experimental values were consistent. This verified the adequacy of these predicted models. It was concluded that RSM was appropriate for the optimisation of banana puree fermentation using cell immobilised L. acidophilus, and products with better synbiotic effects could be obtained. The consumer palatability of the immobilised cell-fermented banana puree was found to be acceptable.
International Journal of Food Science & Technology 12/2008; 44(1):120 - 127. · 1.26 Impact Factor
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ABSTRACT: Lactobacillus acidophilus was entrapped in κ-carrageenan and used to perform tomato juice fermentation in order to raise the survival of the bacteria in the product. Gel beads with diameters approximately 3.0 mm for cell immobilization were obtained, fresh raw tomatoes were used to make the juice and both free and immobilized cells were applied to carry out the fermentation for 80 h. Cell leakage from the gel beads and proliferation in the juice during the fermentation of immobilized cells were observed. The final viable cell number was attained with 107 cfu/mL in the juice, over 1010 cfu/mL-gel in gel beads for the fermentation of immobilized cell, and ca. 109 cfu/mL for the free cell. Immobilized cells could withstand the unfavorable low pH environment in tomato juice and better growth was achieved compared with free cells. The viable cell counts of immobilized L. acidophilus in the fermented tomato juice could maintain the level of 106 cfu/mL-gel after 10 weeks of cold storage at 4C, in comparison with 104 cfu/mL for free cells. The immobilized cell fermented tomato juice also showed better overall palatability than that of free cells in cold storage at 4C.PRACTICAL APPLICATIONSThis study demonstrates the applicability of κ-carrageenan immobilized Lactobacillus acidophilus in the fermentation of tomato juice. The unfavorable low pH condition in tomato juice could be overcome and certain benefits were provided by cell immobilization.
Journal of Food Processing and Preservation 03/2008; 32(2):178 - 189. · 0.55 Impact Factor
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ABSTRACT: Freeze-drying was applied as a drying method for the production of dehydrated immobilized Lactobacillus acidophilus-fermented banana medium containing high levels of probiotics and appropriate prebiotic (mainly fructooligosaccharides) contents in an attempt to develop dried synbiotic products. Ca-alginate and κ-carrageenan were used for the immobilization of L. acidophilus, and the immobilized bacteria were employed directly in the banana media fermentation. The fermented products were then freeze-dried. Results indicated that cell immobilization could provide effective protection to L. acidophilus, and reduce the damage caused by freezing and freeze-drying. Meanwhile, accelerated storage testing using temperatures of 50, 60 and 70C was applied to the dehydrated products. Gel-entrapped L. acidophilus appeared to have lower decimal reduction, and Ca-alginate immobilized cells had a better survival than κ-carrageenan. Results of accelerated storage test showed that immobilization could effectively increase the thermal resistance of entrapped microorganisms, and Ca-alginate showed a better effect than κ-carrageenan, and the beneficial effects increased with the decrease of the storage temperature. The freeze-dried products exhibited little hygroscopicity because of the consumption of monosaccharides during fermentation. Results revealed that freeze-drying could be used as a proper method for the development of dried product of immobilized L. acidophilus-fermented banana media, and accelerated storage test could be used to evaluate the storage stability of the dried products.PRACTICAL APPLICATIONSThis research demonstrates the feasibility of the application of accelerated storage testing to the prediction of shelf life and storage stability of freeze-dried probiotic products manufactured by lactic acid bacteria fermentation. The Arrhenius equation was associated in this study. This will provide an efficient approach for the estimation of shelf life of probiotic products.
Journal of Food Processing and Preservation 12/2007; 31(6):688 - 701. · 0.55 Impact Factor
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ABSTRACT: Lactobacillus reuteri shows certain beneficial effects to human health and is recognized as a probiotic. However, its application in frozen foods is still not popular because of its low survival during freezing and frozen storage. Cell immobilization technique could effectively exert protection effects to microbial cells in order to enhance their endurance to unfavorable environmental conditions as well as to improve their viability and cell concentration. Ca-alginate and kappa-carrageenan were used to immobilize L. reuteri in this research, and the immobilized cells were exposed to different freezing temperatures, i.e. -20 degrees C, -40 degrees C, -60 degrees C, -80 degrees C, and stored at -40 degrees C and -80 degrees C for 12 weeks. The objectives were to study the protection effects of cell immobilization against the adverse conditions of freezing and frozen storage, and the effects of freezing temperatures to the immobilized cells. Cell immobilization was used to raise the survival of L. reuteri during freezing and frozen storage in order to develop frozen foods with the probiotic effects of L. reuteri. Results indicated that immobilized L. reuteri possessed better survival in both freezing and frozen storage. The survival of immobilized L. reuteri was higher than that of free cells, and the effects of lower freezing temperature were better than higher freezing temperature. The immobilization effects of Ca-alginate were found to be superior to kappa-carrageenan. Cell immobilized L. reuteri exhibits potential to be used in frozen foods.
Journal of Microbiological Methods 10/2007; 70(3):561-4. · 2.09 Impact Factor
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ABSTRACT: The basic characteristics of the spore-forming lactic acid bacterium, Sporolactobacillus inulinus BCRC 14647, was evaluated in vitro for its potential probiotic properties. Assessments including acid and bile salt tolerance, adhesiveness, and antagonistic effects on pathogenic Salmonella enteritidis BCRC 10744, as well as inhibition factors of spent culture supernatant (SCS) and an invasion assay, were conducted using Lactobacillus acidophilus BCRC 10695 and two bifidobacteria (Bifidobacterium bifidum BCRC 14615 and B. longum BCRC 11847) as a reference. In the results, S. inulinus spores presented significantly higher survival rates than the vegetative cell form in acidic conditions as well as the reference bifidobacteria. However, L. acidophilus showed the highest viability among all tested strains. Similar results were found in the bile tolerance test. Compared with the reference strains, the vegetative cell form of S. inulinus possessed a proper adhesive characteristic (71.7 bacteria/field for S. inulinus and 91.3 and 45.7 bacteria/field for B. bifidum and B. longum, respectively). In the adhesion assay, both the spore form of S. inulinus (17.1 bacteria/field) and the negative control, L. bulgaricus BCRC 14009 (5.9 bacteria/field), displayed nonadhesive traits. The vegetative cells of S. inulinus and its SCS both dramatically decrease the adhesion of S. enteritidis to Caco-2 cells; meanwhile, the SCS of S. inulinus vegetative cells inhibited the growth of S. enteritidis in the inhibition zone test. The existing inhibition factor could be assumed to be lactic acid in the SCS. From the results of the invasion assay, S. inulinus showed high safety properties. In conclusion, based on these in vitro evaluations, results suggest that S. inulinus presents probiotic features of great potential in the vegetative cell form.
Current Microbiology 06/2007; 54(5):396-404. · 1.82 Impact Factor
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ABSTRACT: Fermentation media were prepared by using banana as the raw material, and cell immobilization of Lactobacillus acidophilus by kappa-carrageenan entrapment was applied to enhance the fermentation efficiency. Gel beads of diameters around 3.0 mm were prepared for the immobilized cells, ripe bananas were used for preparation of media, and both free and immobilized cells were employed to carry out the fermentation for 80 h. Cells leaked out from the gel beads and proliferated in the medium solution during the fermentation of immobilized cells. The final viable cell number reached 10(5) CFU/ml in the medium suspension, over 10(8) CFU/(ml gel) in gel beads for the immobilized cell fermentation and around 10(6) CFU/ml for the free cell fermentation. Immobilized cells withstand the adverse conditions in banana media resulting in better fermentation efficiency compared to free cells. Variation of fructooligosaccharides (FOS) in banana media was not significant in immobilized cell fermentation compared to free cell. Immobilized L. acidophilus fermented banana medium was found to possess synbiotic properties.
International Journal of Food Microbiology 04/2004; 91(2):215-20. · 3.33 Impact Factor
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The Journal of General and Applied Microbiology 01/2004; 49(6):357-61. · 0.98 Impact Factor
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ABSTRACT: An experimental dryer was developed to determine the drying characteristics of sweet potato during freeze-drying with far-infrared radiation. The experimental drying time of sweet potato cubes dehydrated by three drying methods, i.e., air-drying, freeze-drying, and freeze-drying with far-infrared radiation, were compared, and freeze-drying with far-infrared radiation was found to be able to reduce the drying time of sweet potato. Both constant and falling rate drying periods were observed, and empirical equations were developed to study the behavior of drying rate in falling rate period. On the other hand, four mathematical models were used to describe the drying characteristics of sweet potato during freeze-drying with far-infrared radiation. The coefficients of determination (R2) in the exponential, Page, and approximate diffusion model were found to be above 0.98, and that of diffusion model was above 0.92. The rank of fitness of those models was Page, approximate diffusion, exponential and diffusion model. The choice of Page model was evident because of the lowest residual as well as RMSE. The Page model described the far-infrared freeze-drying characteristics of sweet potato properly.
Journal of Food Engineering.
