A number of health benefits have been claimed for probiotic bacteria as Lactobacillus casei. Probiotics have been used therapeutically to modulate immunity, lower cholesterol, treat rheumatoid arthritis, prevent cancer, improve lactose...
moreA number of health benefits have been claimed for probiotic bacteria as Lactobacillus casei. Probiotics have been used therapeutically to modulate immunity, lower cholesterol, treat rheumatoid arthritis, prevent cancer, improve lactose intolerance, and prevent or reduce the effects of atopic dermatitis, diarrhea, and constipation. Dairy and fermented foods have been used as carriers to reintroduce a viable population of probiotics into the gastrointestinal tract of children and adults; however various studies have shown that probiotic organisms survive poorly in yogurt and fermented milks because they do not tolerate exposure to acidic and aerobic environments [1]. In addition the usual starter organisms in yogurt are not bile-tolerant and do not colonize the intestines. It is necessary to produce yogurts added with lactic acid bacteria that are resistant to the stressful conditions of the stomach and the upper intestine, which both contain bile [2]. Encapsulation methods have been recognized as alternatives to protect viable cells of probiotic microorganisms. Microencapsulation is a process in which the cells are retained within an encapsulating matrix or membrane. Most studies on the development of protective matrixes for probiotic bacteria have targeted viability in gastrointestinal conditions. However few studies are available regarding the viability of microencapsulated probiotic microorganisms in foods during the processing and the storage time. The objective of this project was to investigate the effect of sodium alginate (A) blended with low-methoxyl pectin (P) or modified starch (AM) as wall materials of microcapsules containing Lactobacillus casei on the size, morphology and yield of microcapsules produced by extrusion, and the survival of encapsulated Lactobacillus casei in yogurt during storage time. Six treatments of microcapsules were prepared using a dispersion of A (FD 175, CP Kelco, México) (0.5% w/v) blended with P (LM-04 AS-BG, CP Kelco, México) or AM (06436, Cerestar EUA, Inc.): T P1 , T P2 y T P3 containing P at 1, 2 and 3 % (w/v), respectively, and T A1 , T A2 y T A3 containing AM at 1, 2 and 3 % (w/v), respectively. All wall materials aqueous dispersions were pasteurized (63 ºC, 30 min) and allowed to cool to 25 °C. To 36 mL of each of the wall materials dispersions were added 4 mL of late log-phase culture of Lactobacillus casei 81 LYO (Danisco, Inc. EUA) so that a level of 8.9 log cfu mL-1 of wall materials dispersion was reached. Extrusion [3] was performed by expression of the wall material-culture mixture through an insulin syringe needle dropwise into 0.5 M CaCl 2. Microcapsules were held at 25 °C for 12 h to ensure complete solidification. Microcapsules were separated by filtration through of a stainless mesh with 0.19 mm of mesh and stored in sterile whole milk powder dispersion (6 % w/v) at 4 °C until its use and characterization. The size of twenty microcapsules of each treatment was measured using a micrometer. External and internal appearance of the microcapsules was examined by Scanning Electron Microscopy (JMS-035, Jeol Ltd., Akishima, Japan) at an accelerating voltage of 20 kV. Microcapsules samples were fixed in 0.1 M phosphates buffered (pH 7.2) 2.0 % (v/v) glutaraldehyde solution and washed with a series of 50 % to 100 % ethanol concentrations and critical point-dried (Technics CPA II Critical Point Dryer (Tousimis, Rockville, MD). Dry sections were fractured with a blade and fragments were mounted on aluminum SEM stubs, and vacuum gold coated (Fine Coat Jeol-JFC-1100 (Jeol Ltd., Akishima, Japan). In order to determine the viable counts of the entrapped bacteria 1 g of microcapsules were 250
