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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.
- Volatile and quality changes in fresh-cut cantaloupe and honeydew melons stored in modified atmosphere packagingPublication . Amaro, Ana L.; Beaulieu, John C.; Almeida, Domingos P. F.; Malcata, F. X.
- Interesterification and acidolysis of butterfat with oleic acid by Mucor javanicus lipase: changes in the pool of fatty acid residuesPublication . Balcão, Victor M.; Malcata, F. X.Lipases have become powerful tools in the manufacture of structured fats either via randomization of their glyceride composition or incorporation of externally supplied fatty acid residues in such glycerides. The present communication reports on changes that occurred in the fatty acid pool of anhydrous butterfat subject to interesterification and to acidolysis with oleic acid catalyzed by a commercial lipase immobilized by plain physical adsorption onto hydrophobic hollow fibers at 40°C under controlled water activity. The main goal of this research effort was to engineer butterfat so as to increase its level of unsaturated fatty acid residues and concomitantly decrease its level of medium- and long-chain saturated fatty acid residues (viz. lauric and myristic acids). Although a certain degree of net hydrolysis of butterfat was observed, the triacylglycerols of butterfat subject to acidolysis were found to possess more (approximately 30% w/w) oleic acid and significantly less (8% w/w) lauric acid and less (2% w/w) myristic acid than those of the original butterfat.
- 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
- Effects of addition of sucrose and salt, and of starvation upon thermotolerance and survival during storage of freeze-dried Lactobacillus delbrueckii ssp bulgaricusPublication . Carvalho, A. S.; Silva, J.; Ho, P.; Teixeira, P.; Malcata, F. X.; Gibbs, P.Increased survival of freeze-dried cells of Lactobacillus bulgaricus was observed when the drying medium was supplemented with sucrose; however, the magnitude of such protection was dependent on the growth medium used. Supplementing the growth medium with NaCl markedly increased survival of dried cells, and only a small effect was exerted by the composition of the drying medium or prior to starvation of cells. The D57 values of Lactobacillus bulgaricus cells grown in MRS were about half of those of cells grown in MRS supplemented with sucrose, with sucrose plus NaCl, or with NaCl.