Browsing by Author "Rodrigues, D."
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- Development of a non-dairy probiotic fermented rice food with bifidobacterium animalis and streptococcus thermophilusPublication . Gomes, A; Rodrigues, D.; Baltazar, B.; Sousa, S.; Vasconcelos, Marta; Pimenta, Ana; Freitas, A.
- Effect of storage conditions on stability of free and encapsulated – in plain or cysteine-supplemented alginate, Lactobacillus acidophilus KiPublication . Sousa, S.; Gomes, A.; Pintado, M.; Silva, J.; Costa, P.; Amaral, M.; Rocha-Santos, T.; Rodrigues, D.; Freitas, A.Lately, many functional food products have been widely released. Functional foods are foods which promote health beyond providing basic nutrition (Sanders, 1998). Probiotic bacteria are currently used in the development of functional food products (Pimentel-González, 2009; Siró et al., 2008), yet sometimes face technological challenges when incorporated in food matrices with more aggressive environments – salt, acid or oxygen concentrations. In order to be effective, the suggested concentration for probiotic bacteria is 106 CFU/g of a product (Shah, 2000). Encapsulation is an efficient technique to overcome such difficulties since microcapsules help in their protection from both the product intrinsic properties and the gastrointestinal tract conditions. Besides the challenges originated by the food matrices and the gastrointestinal tract there is also the challenge of conservation of the viable microorganisms throughout production and storage of the delivery food product which is also a reason for encapsulating probiotics (Allan-Wojtas et al., 2008) since the encapsulation technique can also help to protect the probiotics from the storage conditions of the product and thus increase its shelf-life in which the microorganisms are inside their effectiveness range. In this research work stability of calcium alginate capsules, produced by extrusion by aerodynamically assisted flow, throughout six months storage was studied. The effect of four storage temperatures (21, 4, -20 and -80 ºC) upon the viability of free and encapsulated cells of Lactobacillus acidophilus Ki was assessed. Two types of microcapsules were produced – one with calcium alginate and another where L-cysteine·HCl was utilized as a supplement to the calcium alginate matrix.
- Effect of storage conditions on stability of free and encapsulated in plain- or cysteine-supplemented alginate, Bifidobacterium animalis BB-12®Publication . Sousa, S. C.; Costa, E. A.; Gomes, A. M.; Pintado, M. M.; Malcata, F. X.; Silva, J. P.; Lobo, J. M. Sousa; Costa, P.; Amaral, M. H.; Bahia, M. F.; Rocha-Santos, T.; Rodrigues, D.; Freitas, A. C.The main objective of this research work was to study the viability of Bifidobacterium animalis BB-12® as free and calcium alginate-encapsulated cells, with or without cysteine, throughout storage, at four different temperatures. Extrusion by aerodynamically assisted flow was used to produce alginate and calcium alginate supplemented with L-cysteine·HCl microcapsules, containing B. animalis BB-12®. The microcapsules were suspended in Ringer solution in a 1:9 (g/mL) ratio, and stored at 21, 4, -20 and -80 ºC throughout six months, respectively. In parallel, the viability of free cells in cell suspension, was subjected to the same storage conditions and the corresponding viability assessed. Results showed that at 21, 4 and -20 ºC, the encapsulation did not have a protective effect—free cells maintained their viability throughout longer periods than encapsulated counterparts. At -80 ºC, encapsulation protected B. animalis BB-12® in comparison to the behavior of free cells. However, this effect was only observed in calcium alginate microcapsules supplemented with L-cysteine.HCl. After 180 days storage at -80 ºC, a 2 log cycle difference, in viable cells was observed between microcapsules with or without cysteine. The viable numbers of B. animalis BB-12® in microcapsules without cysteine was similar to that of free cells. In conclusion, alginate encapsulation revealed a protective effect on viability of B. animalis BB-12® stored at -80 ºC when supplemented with L-cysteine.HCl.
- Encapsulation protective effect upon viability of probiotic bacteria throughout storage and gastrointestinal tractPublication . Rodrigues, D.; Sousa, S.; Rocha-Santos, T.; Gomes, A. M.; Pintado, M. M.; Malcata, F. X.; Silva, J. P.; Lobo, J. M. S.; Costa, P.; Amaral, M. H.; Freitas, A. C.Microcapsules (MC) with fresh cultures of potential probiotic strains (Lactobacillus paracasei LAFTI® L26, L. acidophilus Ki and Bifidobacterium animalisBB-12®) were produced by spray-drying using whey protein concentrate (WPC50) with or without L-cysteine (0.5 g/L). After microencapsulation, the MC were stored, in duplicate, at 5ºC over a period of 6 months during which the number of viable cells (VC) were evaluated. After 15, 60 and 120 days of storage, their resistance throughout gastrointestinal conditions was evaluated. In MC without L-cysteine, the VC numbers of L. acidophilus Ki and B. animalis BB-12® after 6 months of storage decreased from 108 to 106 cfu/g whereas no decrease was observed for L. paracasei. The presence of L-cysteine revealed a positive effect, especially for L. acidophilus Ki after 90 days of storage accounting for more than one logarithm cycle increase in viability. Encapsulation had a protective effect on the three probiotic strains when exposed to the gastrointestinal conditions in comparison to their free cells. This effect was particularly significant for L. acidophilus Ki in conditions similar to those of ileum/duodenum including the presence of pancreatin and bile salts. Storage time did not affect the resistance of the three probiotic strains to the gastrointestinal conditions.
- Influence of L-cysteine, oxygen and relative humidity upon survival throughout storage of probiotic bacteria in whey protein-based microcapsulesPublication . Rodrigues, D.; Sousa, Sérgio; Santos, Nathália Baptista T.; Silva, J.P.; Lobo, J. M. Sousa; Costa, P; Amaral, Gustavo Henrique De Oliveira; Pintado, M.M.E; Gomes, Ana Maria; Malcata, F. Xavier; Freitas, Ana CThe survival rates of Lactobacilus acidophilus Ki, Lactobacillus paracasei L26 and Bifidobacterium animalis BB-12 were studied after whey protein microencapsulation via spray-drying, with or without L-cysteine-HCl, and storage up to 6 months at 5 degrees C and 22 degrees C, with variation in relative air humidity and oxygen levels. Lb. paracasei L26 was the least susceptible to storage conditions: above 10(6) cfu g(-1) were recorded by 180 d at 22 degrees C, irrespective of relative humidity, and the presence/absence of oxygen and L-cysteine. Higher relative humidity, higher temperature and longer storage periods were deleterious to survival of both B. animalis BB-12 and Lb. acidophilus Ki; the effect of L-cysteine-HCl was dependent on the probiotic strain. The effect of overhead oxygen was not significant upon any probiotic strain studied. Whey protein microcapsules containing L-cysteine-HCl protected probiotic cultures from simulated gastrointestinal conditions.
- Occurrence, identification, and characterization of campylobacter species isolated from portuguese poultry samples collected from retail establishmentsPublication . Mena, C.; Rodrigues, D.; Silva, J.; Gibbs, P.; Teixeira, P.Campylobacter spp. are a leading cause of human diarrhea. The common source of infection is contaminated food, particularly poultry. From May 2005 to October 2006, 164 samples of poultry obtained from several retail establishments and from different Portuguese producers were analyzed for the presence of Campylobacter spp.Atotal of 99 Campylobacter strains were isolated and further identified. Susceptibilities for 44 strains were determined for 11 antimicrobial drugs by the agar diffu-sion technique. According to the minimal inhibitory concentration for 90% of the isolates, resistance to tetracycline, nalidixic acid, rifampicin, erythromycin, vancomycin and penicillin was observed. Sensitivity to gentamycin and chloramphenicol was also demonstrated. According to the antibiotic resistance profiles, the isolates appeared to differ from each other, including those that had been collected at the same period of time and from the same chicken sample.