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| Author(s): |
Alcina Maria Liserre
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2005-08-19 |
| Examining board members: |
Bernadette Dora Gombossy de Melo Franco;
Carlos Raimundo Ferreira Grosso;
Mariza Landgraf;
Maria Inês Ré;
Salvador Massaguer Roig
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| Advisor: | Bernadette Dora Gombossy de Melo Franco |
| Abstract | |
Bifidobacterium spp. are microorganisms that can be added to foods. However, the benefits for the human health occur when the numbers of viable cells in the moment of the consumption is at least 106CFU/g. Bifidobacteria are acid sensitive, and methods to protect cell integrity, such as microencapsulation, are needed. In the first part of the present study, Bifidobacterium lactis was encapsulated in microparticles of alginate and modified alginate (alginate-chitosan, alginate-chitosan-sureteric and alginate-chitosan-acryl-eze) and the survival and release from microparticles in simulated gastrointestinal conditions were measured, using buffers (pH 1.5, 5.6 and 7.5), in the absence and presence of pepsin (3g/L), pancreatin (1g/L) and bile. The release from microparticles presented a direct relationship with pH. When the pH was 1.5 and no enzyme was present, encapsulation improved the survival of B. lactis, when compared to free cells. However, pepsin had a protective effect on B. lactis, and the survival rate was directly related to the cells injury degree. In the second part of the study, fermented milk samples containing Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus were supplemented with B. lactis submitted to four different treatments: dehydration at room temperature, freeze drying, encapsulation in alginate-chitosan and encapsulation in alginate-chitosaacryl-eze. The number of viable B. lactis cells in the fermented milk was determined weekly and also after treatment with simulated gastrointestinal conditions. Results indicated that in the absence of pepsin, the number of viable cells decreased significantly after contact with buffers (pH 1.5), and no viable cell was detected after 120 minutes. Pepsin improved the recovery of viable cells in the assayed gastric conditions, being the dehydrated cultures more resistant than other cultures. In fermented milk containing the dehydrated cells, the number of viable cells increased after treatment with simulated gastrointestinal fluids. Microencapsulation was not an effective procedure to protect B. lactis in fermented milk against injury caused by the simulated gastrointestinal tract. (AU) | |