Percorrer por autor "Pereira, C. I."
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- Contribution of specific adventitious microorganisms toward evolution of sugar and organic acid orofiles throughout ripening of model portuguese cheesesPublication . Pereira, C. I.; Franco, M. I.; Gomes, E. O.; Gomes, Ana M. P.; Malcata, F. X.Model cheeses, designed to mimic Portuguese traditional cheeses, were manufactured aseptically following a method that attempted to resemble artisanal manufacture practices: they were coagulated with either animal or plant rennet, and inoculated with defined strains of lactic acid bacteria, that had initially been recovered as major constituents of the native microflora of Serra da Estrela cheese, viz. Lactococcus and Lactobacillus genera, either independently or as a mixture. The gross composition, the microbial viability, and the organic compound profile in those model cheeses were monitored, throughout a 60 day-ripening period. Microbial viability, pH, and levels of acetic and lactic acids were the physicochemical and biological parameters that experienced the most significant changes in such matrices – which were, in turn, dependent on the type of inoculum used. No synergisms emerged upon combination of the two strains, in terms of sugar uptake and organic acid release. The contribution of each adventitious bacterium – either independently or in the presence of each other, to the development of expected biochemical characteristics of model cheeses (even though to a lower extent than in actual ones) was confirmed, whereas the type of rennet used proved to be not relevant.
- Glycolysis and proteolysis in Portuguese model cheeses: role of isolated lactic acid bacteria and coagulantPublication . Pereira, C. I.; Gomes, E. O.; Gomes, Ana M. P.; Malcata, F. X.Portuguese model cheeses were developed and manufactured according to traditional manufacturing practices. Sterile milk was divided into different batches and inoculated with well-defined starter cultures, comprising one Lactococcus, one Lactobacillus or the mixture of the two. The starters, in combination with either an animal or plant coagulant, were assessed for their effect on gross composition, production of organic compounds and proteolysis over a 60-day ripening period. The organic acids formed and the pattern of protein degradation were dependent on the experimental conditions while distinct patterns were observed for each starter strain or combination of strains.
- How three adventitious lactic acid bacteria affect proteolysis and organic acid production in model portuguese cheeses manufactured from several milk sources and two alternative coagulantsPublication . Pereira, C. I.; Neto, D. M.; Capucho, J. C.; Gião, M. S.; Gomes, Ana M. P.; Malcata, F. X.Model cheeses were manufactured according to a full factorial experimental design to help shed light on the individual and combined roles played by 3 native lactic acid bacteria (Lactococcus lactis ssp. lactis, Lactobacillus brevis, and Lactobacillus plantarum) upon proteolysis and organic acid evolution in cheese. The model cheeses were manufactured according to a generally representative Portuguese artisanal protocol, but the (ubiquitous) adventitious microflora in the cheesemaking milk were removed via sterilization before manufacture; therefore, the specific effects of only those lactic acid bacteria selected were monitored. In addition, 2 types of coagulant (animal and plant) and 3 types of cheesemaking milk (cow, sheep, and goat) were assessed to determine their influence on the final characteristics of the model cheeses. The nature of the coagulant appeared to be essential during the first stage of proteolysis as expected, whereas the contribution of those bacteria to the pools of total free AA and organic acids was crucial afterward. This was especially so in terms of the differences observed in the metabolisms of lactic acid (in the case of Lactococcus spp.) as well as acetic and citric acids (in the case of Lactobacillus spp.).
- Survival of probiotic bacteria in a whey cheese vector submitted to environmental conditions prevailing in the gastrointestinal tractPublication . Madureira, A. R.; Pereira, C. I.; Truszkowska, K.; Gomes, Ana M. P.; Pintado, M. E.; Malcata, F. X.Various foods may be used to deliver probiotic bacteria into the gastrointestinal tract; one such example is Requeijão, a Portuguese whey cheese. Survival and stability of Bifidobacterium animalis strains BLC-1, Bb-12, and Bo, Lactobacillus acidophilus strains LAC-1 and Ki, L. paracasei ssp. paracasei strain LCS-1 and L. brevis strain LMG 6906 inoculated into Requeijão, when exposed to simulated gastrointestinal tract conditions, were assessed. Homogenates of inoculated whey cheese in 0.85% (w/v) sterile saline water were exposed to a solution of hydrochloric acid (pH 2.5–3.0) and pepsin (1000 unitsmL–1) at 371C, and then to 0.3% (w/v) bile salts after 60 or 120 min of acid exposure. All bacterial strains retained their initial viable cell numbers. Bifidobacterium animalis strains Bb-12 and Bo, and L. brevis strain LMG 6906 exhibited the highest viable cell numbers when exposed to bile salts, whereas the other strains had variable death rates.