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- Manufacturing of fermented goat milk with a mixed starter culture of Bifidobacterium animalis and Lactobacillus acidophilus in a controlled bioreactorPublication . Kongo, J. M.; Gomes, Ana M. P.; Malcata, F. XavierAims: This work was undertaken to study the feasibility and the characteristics of a fermented product made of goat milk, using a mixed starter culture of Bifidobacterium animalis and Lactobacillus acidophilus under controlled conditions, and to determine their survival in the fermented milk during refrigerated storage. Methods and Results: Goat milk was inoculated with Lact. acidophilus and Bif. animalis mixed starter, fermented in a glass bioreactor with controlled temperature (37 C) and anaerobiosis, and monitored for growth and acidification. The fermented milk was then stored for 10 days under refrigeration, and monitored daily for starter microflora survival and pH changes. Lact. acidophilus viable counts reached a maximum of 7Æ1 · 108 colony-forming units (CFU) ml)1, and Bif. animalis a maximum of 6Æ3 · 107 CFU ml)1 by 20 h of fermentation. During refrigerated storage, both strains exhibited a good survival, with viable numbers remaining essentially constant throughout the experiment, whereas the pH of the fermented milk dropped slightly. Conclusions: Mixed cultures of Bif. animalis and Lact. acidophilus may be used to produce fermented goat milk with high counts of both probiotic strains. Significance and Impact of the Study: Goat milk fermented with Bif. animalis and Lact. acidophilus can be manufactured as an alternative probiotic dairy product.
- Separation of neutral lipid classes by high-performance liquid chromatography using light-scattering detection: analysis of vegetable oils and maize flourPublication . Rocha, João M.; Kalo, Paavo J.; Ollilainen, Velimatti; Malcata, F. Xavier
- Alternative formulation of the problem of mass transfer during bubble formation in the presence of an interfacial chemical reactionPublication . Malcata, F. XavierThe removal of a dilute solute from a gas mixture being injected through a submerged single nozzle with an instantaneous chemical reaction occurring on the gas/liquid interface is theoretically studied. An improved version of the double surface-renewal model for the molecular transport of solute is reported. The reasoning underlying this improvement arises from the decoupling of the bulk and overall concentration of solute in the bubble, and requires an extra parameter for full description. An analytical formula pertaining to the overall depletion of solute by reaction with time is obtained. Simplifications of this result are presented and discussed f or asymptotic behaviors. The propriety of the analysis for the modeling of experimental evidence is included.
- Microbiological profile in sourdough: evolution during refrigerated storage.Publication . Rocha, João M.; Malcata, F. Xavier
- Antimicrobial Susceptibility of Enterococci Isolated from Terrincho CheesePublication . Pimentel, L. L.; Novais, C.; Pintado, M. E.; Gomes, Ana M. P.; Coque, T.; Sousa, J. C; Malcata, F. Xavier; Peixe, L.
- Enhancement of product selectivity via enzyme immobilization in sequential degradation reactions of polymeric substratesPublication . Varga, S.; Malcata, F. XavierThe balance equations pertaining to the modelling of a slap-shaped bead containing immobilized enzyme uniformly distributed which catalyzes the sequential reactions of degradation of a polymeric substrate were written and analytically solved in dimensionless form. The effect of the Thiele modulus on the selectivity of consumption of each multimeric product was studied for a simple case. Whereas plain diffusional regime leads to lower selectivities than plain kinetic regime, improvements in selectivity of species A i relative to species Ai+1 may be obtained at the expense of higher Thiele moduli within a limited range when the diffusivity of A i is larger than that of A i +1, or when the pseudo first order kinetic constant describing the rate of consumption of A i is lower than that of Ai+1.
- Microstructural, physicochemical and sensorial effects of pears (cv. Rocha) stored under controlled atmosphere conditionsPublication . Galvis-Sánchez, Andrea C.; Teixeira, Claudia; Fonseca, Susana C.; Malcata, F. Xavier
- Determination of antioxidant capacity using the biological system bacteriophage P22/bacterium salmonella typhimuriumPublication . Gião, Maria S.; Borges, André B.; Guedes, Catarina J.; Hogg, Tim; Pintado, Manuela E.; Malcata, F. XavierBacteriophage/bacterium systems have been employed in the past in assays for virucidal activity. A novel application of one such system is proposed here for the in vivo determination of antioxidant capacity. It was shown that an antioxidant such as gallic acid can effectively protect against oxidative damage brought about by H2O2sbut only within a narrow range of concentrations (i.e., from 250 to 500 mg L-1); ascorbic acid, on the other hand, did not exhibit any protective effect against H2O2. Finally, neither ascorbic nor gallic acid demonstrated a virucidal effect. The P22/Salmonella typhimurium model system thus proved to be useful in the assessment of antioxidant capacity in vivo, at least using those two alternative model antioxidants.
- Hydrolysis of whey proteins by proteases extracted from Cynara cardunculus and immobilized onto highly activated supportsPublication . Lamasa, Estela M.; Barrosa, Rui M.; Balcão, Victor M.; Malcata, F. XavierBlends of cardosins A and B, enzymes present in aqueous extracts of the flowers of the thistle (Cynara cardunculus L.), have for long been used as rennets by the cheesemaking industry in the Iberian Peninsula. These dimeric proteases are present in the stigmæ and stylets of said flowers, and are thought to play a role in sexual reproduction of the plant. In the present research effort, production of cardosin derivatives (starting from a crude extract), encompassing full stabilization of their dimeric structure, has been attempted via covalent, multi-subunit immobilization onto highly activated agarose-glutaraldehyde supports. Boiling such enzyme derivatives in the presence of sodium dodecyl sulfate and β-mercaptoethanol did not lead to leaching of enzyme, thus proving the effectiveness of the attachment procedure. Furthermore, derivatives prepared under optimal conditions presented ca. half the specific activity of the enzyme in soluble form, and were successfully employed at lab-scale trials to perform (selective) hydrolysis of α-lactalbumin, one of the major proteins in bovine whey.
- Contribution of wild strains of lactic acid bacteria to the typical aroma of artisanal cheesePublication . Tavaria, Freni; Ferreira, A. César Silva; Malcata, F. Xavier