Browsing by Issue Date, starting with "1996"
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- Os direitos do homem e a lei natural em Jacques MaritainPublication . Alves, José Anastácio de Gouveia
- 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.
- Modelling the thermal sterilisation of foods inside packs with two divisionsPublication . Ávila, Isabel M. L. B.; Manso, Maria da Conceição; Silva, Cristina L. M.A mathematical model was developed to describe the heat transfer during the sterilisation of conduction heating foods inside three dimensional two division rectangular packs. The model uses a standard explicit finite differences method with non-capacitance surface nodes and simulates different pack sizes, food properties and surface heat transfer resistances at the package lid and walls. Taking into account the cooling phase, the sterility value was calculated as a function of position in order to identify the location of the least lethality point. The most important variables affecting the position of this point are the product heating rate and the surface heat transfer coefficients. For low heating rate values this critical point moves towards the surface. When different food products are sterilised in simultaneously the quality degradation of foods in this type of package is also a point of discussion.
- The use of yeast inoculation in fermentation for port production; effect on total potential ethyl carbamatePublication . Watkins, S. J.; Hogg, T. A.; Lewis, M. J.A commercial wine yeast Saccharomyces cerevisiae UCD 522 (pre-cultured in the presence of certain mass-labelled amino acids) was inoculated into a port must which was then allowed to ferment under controlled conditions of temperature and agitation. The influence of potential ethyl carbamate (EC) precursor formed due to yeast pre-culture, upon total potential EC levels was studied at various stages of fermentation. Pre-culture accumulation did not give rise to detectable levels of EC precursor during port fermentation.
- A Anunciação a Maria: um relato de José? Contributos para o estudo das fontes de Lc.1, 26-38aPublication . Ferreira-Martins, J. M.
- Pesquisa de Listeria monocytogenes em produtos cárneos fumados e de salsichariaPublication . Vaz-Velho, Manuela; Almeida, Gonçalo; Mena, Cristina; Carneiro, Luisa; Freitas, António
- Liberdade contra a vida: Drama da democracia ou perversão da convivência?Publication . Cunha, Jorge Teixeira da
- Potentiometric determination of chloride in vegetables by flow injection analysisPublication . Lima, José L. F. C.; Rangel, António O. S. S.; Souto, M. Renata S.A flow injection system for the potentiometric determination of chloride (Cl) in vegetables is reported. A tubular chloride ion-selective electrode based on a homogeneous crystalline membrane without inner reference solution was used as indicator electrode. A methodology to minimize the influence of the sample matrix on the electrodes response is described. The results obtained with the developed flow injection manifold are in good agreement with those provided by the reference method and present good precision (relative standard deviations lower than 2%). Sample throughput ranges from 150 to 300 determinations per hour
- Changes in the microflora of Serra cheese: evolution throughout ripening time, lactation period and axial locationPublication . Macedo, Angela C.; Costa, M. Luz; Malcata, F. XavierChanges in the microflora and physicochemical characteristics in Serra da Estrela cheese were examined using a three-way factorial design over a 3.5 day ripening period, throughout the lactation period, and for several slices taken normal to the cheese axis. Lactic acid bacteria were the major components of the microflora during ripening throughout the lactation period, but no statistically signtficant differences were detected between the surface and the interior of the cheese. Both enterobacteriaceae and staphylococci in the curd were at maximum numbers during the first week and were still at significant numbers towards the end of the maturation period. The numbers of staphylococci were statistically different between slices and at different times within the lactation period, whereas the numbers of enterobacteriaceae showed statisticalty signrficant variations only throughout the lactation period. Ripening time, lactation period and axial location signtficantly affected the number of yeasts. AN factors studied had statistically significant effects on pH, salt and moisture content; the hypotheses that ripening time, lactation period, and axial location had effects on salt and moisture contents were accepted, in this order, at increasingly lower levels of signtficance; the hypotheses that ripening time, axial location, and lactation period had effects on pH were accepted, in this order, at increasingly lower levels of significance.