Browsing by Author "Pintado, Ana I. E."
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- Acidifying and aromatic properties of enterococcus strains in ovine and bovine milksPublication . Pimentel, L. L.; Soares, J. C.; Pintado, M. E.; Pintado, Ana I. E.; Gomes, Ana M. P.; Ferreira, A. C.; Malcata, F. X.
- Antioxidant activity of sugar molasses, including protective effect against DNA oxidative damagePublication . Guimarães, Carla M.; Gião, Maria S.; Martinez, Sidónia S.; Pintado, Ana I. E.; Pintado, Manuela E.; Bento, Luís S.; Malcata, F. XavierExtracts were obtained from molasses, a byproduct of the sugar industry, via a number of chromatographic steps. Their antioxidant capacity was studied, including the inhibitory effect upon DNA oxidative damage;the phenolic compound profile there of was ascertained as well. Two extracts exhibited significant antioxidant features, expressed by their capacity to decolorize ABTS radical cation and to scavenge hydroxyl free radicals (via deoxyribose assay). Those 2 extracts also brought about protection against induced DNA oxidative damage (via decreasing DNA scission, as assessed by electrophoresis).The phenolic compounds syringic acid,p-hydroxybenzoic acid, vanillic acid, p-hydroxybenzaldehyde, and ferulic acid were positively identified and quantified.
- Caseinolytic activity of fruit extract from Opuntia ficus-indica on bovine, caprine, and ovine Sodium CaseinatesPublication . Pintado, Ana I. E.; Macedo, Angela C.; Teixeira, Grimaneza; Pais, Salomé; Clemente, Alda; Malcata, F. XavierThe rates and extents of hydrolysis of RS- and â-caseins from bovine, caprine, and ovine sodium caseinates produced by an enzymatic extract of the fruit of Opuntia ficusindica, (L.) Miller were evaluated and compared with those produced by a commercial animal rennet. A mechanistic model based on a pseudo-first-order enzymatic reaction, in the presence of first-order deactivation of the enzyme, was postulated and successfully fitted to the experimental data. The animal rennet exhibited higher enzymatic efficiency than the fruit extract, irrespective of the source (i.e., bovine, caprine, or ovine) and the type (i.e., RS- or â-casein) of substrate. The enzymatic efficiency (kcat/Km) for RS-casein ranged from 72 to 220 and from 43 to 65 L g-1 h-1, and for â-casein from 242 to 742 and from 55 to 164 L g-1 h-1, for the animal rennet and the enzymatic extract of O. ficus-indica, respectively. Finally, it was observed that â-casein from caprine and ovine caseinates was degraded by O. ficus-indica faster than its RS counterpart, but the reverse was observed for bovine caseinate.
- Characterization of the microstructure of Terrincho ewe cheesePublication . Gomes, A. M. P.; Braga, T. M.; Pintado, Ana I. E.; Pintado, Maria Manuela; Malcata, F. XavierThe microstructure of Terrincho cheese – a Portuguese traditional cheese bearing a Protected Denomination of Origin, was assessed by scanning electron microscopy (SEM). Terrincho cheese was manufactured according to the traditional protocol using pre-filtered, plain raw ewe’s milk of Churra da Terra Quente breed, without addition of starter of any other type of cultures, and coagulated with animal rennet. The cheeses were salted upon unmoulding, and placed in ripening chambers held at 10–12 °C and 88–89 % relative humidity for a period of 30 days. Cheeses were sampled at 0, 15 and 30 days. Cheese specimens were prepared for SEM by fixing small blocks of cheese (cut from freshly sampled cheeses) in formaldehyde, at room temperature for 1 month, cutting it into 1–2 mm thick slices using sharp razor blades and dehydrating in a graded ethanol series. Slices in absolute ethanol were critical point dried from carbon dioxide, mounted on SEM stubs using adhesive tabs, sputter-coated with gold, and examined using a JEOL scanning electron microscope. The microstructure of the (semi-soft) curd of Terrincho cheese appeared as a continuous casein network possessing a spongy appearance. The various microbial populations present within the cheese were found to grow in the form of colonies, embedded in the casein network and close to the void spaces originally occupied by fat. Microbial colonies were roughly spherical, with bacteria tightly packed in the centre. A similar pattern of microbial growth was observed throughout ripening. Other inclusions were also pinpointed, namely salt crystals.
- Consumer acceptance and sensory profiling of reengineered kitoza productsPublication . Pintado, Ana I. E.; Monteiro, Maria João; Talon, Régine; Leroy, Sabine; Scislowski, Valérie; Fliedel, Geneviève; Rakoto, Danielle; Maraval, Isabelle; Costa, Ana I. A.; Silva, Ana P.; Pallet, Dominique; Tomlins, Keith; Pintado, M. E.Kitoza refers to a traditional way of preparing beef and pork in Madagascar. However, in order to improve some drawbacks previous identified, the product was submitted to a reengineering process. The acceptance and sensory profiling of improved Kitoza products among Portuguese consumers was investigated. A local smoked loin sausage was selected as basis for comparison. Firstly, a Focus Group study was performed to identify sensory descriptors for Kitoza products and explore product perception. Subsequently, a Flash Profile and a consumer sensory acceptance study were conducted. Flash Profile's results showed that beef- and pork-based Kitoza products investigated differed considerably in all sensory dimensions. The Portuguese sausage was characterized as having a more intense and lasting after taste, as well as displaying a higher degree of (meat) doneness. The acceptance study yielded higher overall liking ratings for pork- than for beef-based Kitoza, although the Portuguese sausage remained the most appreciated product.
- Controlled whey protein hydrolysis using two alternative proteasesPublication . Pintado, Manuela E.; Pintado, Ana I. E.; Malcata, F. XavierWhole whey was hydrolyzed for 12 h with Protease 2A and Trypsin using two concentrations of enzyme (20 and 40 g/kgprotein). Samples were assayed for total viable counts of adventitious microflora that survived thermization, total acidity, total concentration of free amino acids, peptide profile and overall degree of hydrolysis. The highest total concentration of free amino acids was observed when hydrolysis was effected by Protease 2A, and the major variations in amino acid qualitative composition occurred between 2 and 6 h: Leu exhibited the most significant increase, followed by Lys, Phe and Ile. Hydrolysis with Trypsin led to release of high amounts of Lys. Quantitative depletion of β-lactoglobulin was observed by 2 h under all processing conditions, and hydrolysis of α-lactalbumin was slower when Trypsin was employed. Formation of peptides was more extensive under the action of Trypsin than of Protease 2A, and the major peptides released by the former had molecular weights mainly in the ranges 7500–8000 and 4000–4500 Da, whereas those released by the latter accumulated in the range 7000–7500 Da. The differences between the hydrolytic actions of Trypsin and Protease 2A were significant except with respect to the concentration of Glu, as well as degree of breakdown of immunoglobulin G and β-lactoglobulin. Growth of adventitious bacteria and generation of free amino acids were successfully modeled using postulated mathematical models. The values of vmax for Trypsin were 0.15 and 0.06 g/(l h) for 40 and 20 g/kgprotein, respectively, and for Protease 2A were 0.86 and 0.50 g/(l h) for 40 and 20 g/kgprotein, respectively.
- Efficiency of purification methods on the recovery of exopolysaccharides from fermentation mediaPublication . Pintado, Ana I. E.; Ferreira, José A.; Pintado, Maria M. E.; Gomes, Ana M. P.; Malcata, F. Xavier; Coimbra, Manuel A.De-Man Rogosa and Sharpe (MRS) is a complex medium commonly used to obtain exopolysaccharides (EPS) from lactic acid bacteria. However, the various nutrients (carbon and nitrogen sources) of media and supplements added to enhance the bacterial growth and EPS production, may interfere with the purification of the extracts resulting in an over-estimation of the EPS and erroneous structural assignments. The efficiency of trichloroacetic acid (TCA)/pronase and 5-sulfosalicylic acid – SSA methods was evaluated. In addition, the interference of the major MRS broth components as well as lactose was evaluated using xanthan gum as model control EPS. It was concluded that MRS medium is a major source of interfering compounds in the quantification of EPS, mainly glucose-rich material and to a lesser extent mannoproteins from yeast extract. This effect was found to be potentiated by the presence of lactose. TCA/pronase method was shown to be more efficient in eliminating interferents.
- Fate of nitrogen during metabolism of whey lactose by Rahnella aquatilisPublication . Pintado, Manuela E.; Pintado, Ana I. E.; Malcata, F. XavierThe rate of intake of peptides and free amino acids by Rahnella aquatilis was studied, as well as the evolution of concentrations of exopolysaccharide, biomass, and several metabolites. For this purpose, eight wheybased fermentation media were tested: hydrolyzed bovine whey under 1) aerobic and 2) anaerobic conditions; hydrolyzed bovine whey with 3) 2.0% (wt/vol) NaCl or 4) 0.5% (wt/vol) NaCl; 5) plain bovine whey; 6) bovine whey permeate; 7) hydrolyzed caprine whey; and 8) hydrolyzed ovine whey. The lower peptide fraction (<2000 Da) in plain whey, whey permeate, and hydrolyzed whey fermented aerobically was virtually depleted by 24 h. In all experiments, most consumption of free amino acids occurred at initial stages of fermentation. In caprine whey, ovine whey, and bovine whey fermented anaerobically, free Val was present at high levels until the end of fermentation, and the highest production of acetic acid was also observed. In ovine whey, high levels of peptides and free amino acids were recorded, as well as the highest production of several organic acids (except lactic acid) and the lowest viscosity and polysaccharide concentration. The low concentration of peptides and free amino acids in plain whey and whey permeate did not apparently permit active consumption of lactose, whereas lack of molecular oxygen and presence of salt played a strong role toward inhibition of exopolysaccharide production. The qualitative and quantitative profile of the nitrogen fraction likely might have determined the metabolism of lactose and, consequently, conditioned the production of exopolysaccharide and organic acids even though growth of R. aquatilis was not affected similarly.
- Identification and characterization of antibiotic susceptibility of enterococci isolated from Terrincho cheesePublication . Pimentel, Lígia L.; Pintado, Manuela E.; Pintado, Ana I. E.; Gomes, Ana M. P.; Malcata, F. Xavier
- Influence of salt content, degree of proteolysis and aeration on the production of a polymer via fermentation of whey-related media by Rahnella aquatilisPublication . Pintado, Manuela E.; Pintado, Ana I. E.; Malcata, F. XavierUtilization of whey as fermentation feedstock has been attempted widely by the dairy industry. Production of lactan, a polysaccharide composed of mannose, galactose and galacturonic acid (at the molar ratio 5:3:2), starting from a semi-defined medium containing lactose via fermentation under aerobic conditions with Rahnella aquatilis was described previously. In this communication, the effect of salt, previous hydrolysis and aeration were studied during the polysaccharide production from whey in alternative fermentation media: hydrolyzed whey (under (i) aerobic and (ii) anaerobic conditions), hydrolyzed whey with 2.0% NaCl (w/v) (iii) and 0.5% NaCl (w/v) (iv),.and plain whey (v). The growth of biomass and the variation in concentration of organic acids, lactose, peptides and free amino acids were monitored. The polysaccharide production and the variation of viscosity of were also followed throughout 48 h of fermentation. Under the different conditions tested, Rahnella aquatillis showed a maximum specific growth rate of 0.61 h-1, 0.60 h-1, 0.61 h-1, 0.64 h-1, and 0.46 h-1 for hydrolyzed whey under aerobiosis and under anaerobiosis, hydrolyzed whey with 2.0% NaCl (w/v) and 0.5% NaCl, and plain whey, respectively; the final yields of the various organic acids were: 0.07, 0.18, 0.07, 0.04 and 0.05 (g/glactose) for acetic acid; 0.06, 0.07, 0.00, 0.04 and 0.02 (g/glactose) for lactic acid; 0.08, 0.09, 0.03, 0.04 and 0.04 (g/glactose) for formic acid; 0.01, 0.04, 0.01, 0.01 and 0.02 (g/glactose) for succinic acid; and 0.11, 0.09, 0.14, 0.19 and 0.00 (g/glactose) for acetoine. Lactose was almost completely depleted during the 48 h of fermentation for hydrolyzed whey; however, lactose was only partly consumed in plain whey (final yield of 0.48 g/glactose).Small peptides (< 2,000 Da) and most free amino acids were consumed by 24 h in hydrolyzed whey fermented under anaerobiosis and plain whey, but these peptides were present until the end of fermentation in the remaining media. R. aquatilis showed similar behavior in free amino acid consumption in hydrolyzed whey with NaCl and hydrolyzed whey fermented under aerobiosis. Plain whey yielded very low concentrations of free amino acids throughout the whole fermentation. The yield of polysaccharide was 0.56, 0.26, 0.39, 0.40 and 0.44 g/glactose for hydrolyzed whey fermented under aerobiosis and under anaerobiosis, hydrolyzed whey with 2.0% NaCl (w/v) and 0.5% NaCl, and plain whey, respectively.
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