F. Xavier Malcata

University of Porto, Oporto, Porto, Portugal

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Publications (270)415.47 Total impact

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    ABSTRACT: Abstract
    Food Research International 12/2014; 66:344-355. · 3.05 Impact Factor
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    ABSTRACT: The purpose of this work was to screen for and characterize the potential probiotic features of strains of lactic acid bacteria isolated from Galega cultivar fermented olives, to eventually develop an improved probiotic food from plant origin. From 156 isolated strains, 10 were acid – and bile salt tolerant, and exhibited survival rates up to 48%, following simulated digestion. All strains exhibited auto- (4–12%) and co-aggregation features (≥30%), as well as hydrophobicity (5–20%) and exopolysaccharide-producing abilities, while no strain possessed haemolytic capacity or ability to hydrolyse mucin. Antibiotic resistance, oleuropein degradation, proteolytic activity and antimicrobial activity were strain-dependent features. Overall, 10 strains – belonging to Lactobacillus plantarum and Lactobacillus paraplantarum, appear to possess a probiotic value.
    LWT - Food Science and Technology. 11/2014; 59(1):234–246.
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    ABSTRACT: The levels of biogenic amines were assessed throughout storage at 4ºC, for up to 120 days, of canned sardines, anchovy and smoked fish. Histamine, tyramine, putrescine, cadaverin, spermidine and spermine levels increased in general with elapsing storage time; the concentrations of the former in sardine, anchovy and smoked fish reached maxima of 281.17 mg/kgdry weight (DW), 166.21 mg/kgDW and 104.51 mg/kgDW, respectively, by 120 days. Spermidine and spermine levels increased slightly, whereas significant differences were found (P<0.05) in the levels of cadaverine and putrescine throughout storage. The total amine contents (579.15 mg/kgDW) of anchovy were highest, followed by sardine (456.86 mg/kgDW) and smoked fish (210.79 mg/kgDW). Overall, canned anchovy and sardine appear to pose public health risks owing to their biogenic amine levels above accepted thresholds.
    Pakistan Journal of Food Sciences. 01/2014; 24(3):137-150.
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    ABSTRACT: In an effort to bypass the adverse secondary effects attributed to the traditional therapeutic approaches used to treat skin disorders (such as atopic dermatitis), alternative antimicrobials have recently been suggested. One such antimicrobial is chitosan, owing to the already proved biological properties associated with its use. However, the influence of abiotic factors on such activities warrants evaluation. This research effort assessed the antimicrobial activity of chitosan upon skin microorganisms (Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli) in vitro when subject to a combination of different abiotic factors such as pH, ionic strength, organic acids and free fatty acids. Free fatty acids, ionic strength and pH significantly affected chitosan's capability of reducing the viable numbers of S. aureus. This antimicrobial action was potentiated in the presence of palmitic acid and a lower ionic strength (0.2% NaCl), while a higher ionic strength (0.4% NaCl) favored chitosan's action upon the reduction of viable numbers of S. epidermidis and E. coli. Although further studies are needed, these preliminary results advocate that chitosan can in the future be potentially considered as an antimicrobial of choice when handling symptoms associated with atopic dermatitis.
    The Journal of Dermatology 12/2013; 40(12):1014-1019. · 2.35 Impact Factor
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    Dataset: science
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    ABSTRACT: The changes in concentration of free amino acids and biogenic amines, along 28 d of storage at 4 °C, were monitored in a wide range of European ripened sausages manufactured from horse, beef and turkey meats. Generally speaking, both chemical families became more concentrated with elapsing time – but rather distinct patterns were followed in each meat type: total free amino acids increased by 13-fold in the case of horse sausages, and 5-fold in the case of beef sausages, but decreased to one third in the case of turkey sausages; and total biogenic amines attained 730 mg/kg in turkey sausages, 500 mg/kg in beef sausages and 130 mg/kg in horse sausages by 28 d of refrigerated storage. For putrescine, maximum levels of 285 mg/kg were attained in turkey and 278 mg/kg in beef sausages; for cadaverine, maximum levels of 6 mg/kg in turkey and 9 mg/kg in beef; and for histamine, maximum levels of 263 mg/kg in turkey and 26 mg/kg in beef. Hence, public safety concerns may be raised in the case of turkey sausages
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    Mohamed A Rabie, Cidalia Peres, F Xavier Malcata
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    ABSTRACT: The changes in concentration of free amino acids and biogenic amines, along 28 d of storage at 4°C, were monitored in a wide range of European ripened sausages manufactured from horse, beef and turkey meats. Generally speaking, both chemical families became more concentrated with elapsing time - but rather distinct patterns were followed in each meat type: total free amino acids increased by 13-fold in the case of horse sausages, and 5-fold in the case of beef sausages, but decreased to one third in the case of turkey sausages; and total biogenic amines attained 730mg/kg in turkey sausages, 500mg/kg in beef sausages and 130mg/kg in horse sausages by 28 d of refrigerated storage. For putrescine, maximum levels of 285mg/kg were attained in turkey and 278mg/kg in beef sausages; for cadaverine, maximum levels of 6mg/kg in turkey and 9mg/kg in beef; and for histamine, maximum levels of 263mg/kg in turkey and 26mg/kg in beef. Hence, public safety concerns may be raised in the case of turkey sausages.
    Meat Science 06/2013; 96(1):82-87. · 2.75 Impact Factor
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    ABSTRACT: Molecular hydrogen (H2) is an ideal fuel characterized by high enthalpy change and lack of greenhouse effects. This biofuel can be released by microalgae via reduction of protons to molecular hydrogen catalyzed by hydrogenases. The main competitor for the reducing power required by the hydrogenases is the Calvin cycle, and rubisco plays a key role therein. Engineered Chlamydomonas with reduced rubisco levels, activity and stability was used as the basis of this research effort aimed at increasing hydrogen production. Biochemical monitoring in such metabolically engineered mutant cells proceeded in Tris/acetate/phosphate culture medium with S-depletion or repletion, both under hypoxia. Photosynthetic activity, maximum photochemical efficiency, chlorophyll and protein levels were all measured. In addition, expression of rubisco, hydrogenase, D1 and Lhcb were investigated, and H2 was quantified. At the beginning of the experiments, rubisco increased followed by intense degradation. Lhcb proteins exhibited monomeric isoforms during the first 24 to 48 h, and D1 displayed sensitivity under S-depletion. Rubisco mutants exhibited a significant decrease in O2 evolution compared with the control. Although the S-depleted medium was much more suitable than its complete counterpart for H2 production, hydrogen release was observed also in sealed S-repleted cultures of rubisco mutated cells under low-moderate light conditions. In particular, the rubisco mutant Y67A accounted for 10-15-fold higher hydrogen production than the wild type under the same conditions and also displayed divergent metabolic parameters. These results indicate that rubisco is a promising target for improving hydrogen production rates in engineered microalgae.
    Applied Microbiology and Biotechnology 05/2013; · 3.69 Impact Factor
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    ABSTRACT: A renewed interest in antioxidants has arisen in recent years; microalgae and cyanobacteria are potential sources thereof for use as food/feed ingredients. However, improved methods for comprehensive screening of antioxidant capacity specifically in intracellular extracts of marine microorganisms are required - encompassing lipophilic and hydrophilic compounds simultaneously. The original ABTS method was thus improved, and in particular the procedures of cell disruption and storage were optimized. The best solvent found was ethanol/water (1:1, v/v). The reaction to form ABTS(+) in said solvent was essentially complete by eight hours, and this radical cation was stable for at least 6days; at room temperature, the ABTS(+) solution remained within an allowable analytical range for up to 13h. Ultra Turrax was the best cell disruption method, and refrigeration was the best preservation method. This improved methodology was validated with four representative strains that respond poorly to cell disruption.
    Food Chemistry 05/2013; 138(1):638-43. · 3.33 Impact Factor
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    ABSTRACT: In the latest decades, dramatic fluctuations of oil prices have occurred – owing to an increasing demand and a more and more limited supply; this situation has urged the quest for renewable energy sources. Microalgal-based biodiesel (MBB) appears as one of the most appealing and feasible substitute for fossil fuels among several cell-based sources of biodiesel. Microalgae are photosynthetic, unicellular organisms that play a vital role in CO2 sequestration in our planet – but they do not competes with food production for arable land and water supply; microalgae may indeed be grown in marginal lands, and use wastewaters or seawater as growth medium. Furthermore, they can synthesize several high added-value products, viz. bioactive compounds, polyunsaturated fatty acids and pigments, which can be extracted prior to lipid extraction itself. After processing, residual algal biomass can still be used as feedstock for other fuels, or else as animal feed. All in all, microalgae offer certainly more advantages for biofuel production than land oil crops normally used for the same purpose. Despite the numerous advantages of MBB, its economic feasibility has been hampered by excessively high (and, thus, still uncompetitive) operation costs. Attempts to effectively address this issue have encompassed either use of lipid-hyperproducing strains, or highly productive, low-cost photobioreactors – coupled with more efficient methods of harvesting and downstream processing. Additionally, full exploitation of all components in microalgal biomass – following a biorefinery strategy, should be considered to alleviate the economic constraint. This chapter addresses these possibilities in a brief, yet integrated manner.
    03/2013: pages 399-430; , ISBN: 9781118523360
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    ABSTRACT: Antioxidants are secondary metabolites in plants, designed to protect them from abiotic stress; however, they may also improve one’s general health, following regular ingestion. Since most foods from plant origin are consumed only after processing and formulation, the final activity exhibited by their antioxidants may be rather different from that in the original plant. Ten plants empirically used in Portugal in traditional medicine were accordingly studied e agrimony (Agrimonia eupatoria), eucalyptus (Eucalyptus globulus), walnut-tree (Juglans regia), myrtle (Myrtus communis), raspberry (Rubus idaeus), sage (Salvia sp.), savory (Satureja montana), sweet-amber (Hypericum androsaemum), thyme (Thymus vulgaris) and yarrow (Achillea millefolium), for total antioxidant capacity and total phenolic content. Significant variations were found between fresh and frozen forms: most plants decreased those features by 30e80 %. However, weather conditions prevailing during plant growth also had a significant impact, besides postharvest storage conditions e especially in the case of antioxidant capacity. Typically, a decrease occurred throughout processing and storage, which was maximum for myrtle and minimum for yarrow. The results of this research are useful in attempts to preserve the antioxidant content of plant-derived foods, or of plant additives in foods, via rational manipulation of processing conditions after harvest and throughout storage.
    Food Science and Technology 01/2013; 50(1):320.
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    ABSTRACT: A growing market for novel antioxidants obtained from non-expensive sources justifies educated screening of microalgae for their potential antioxidant features. Characterization of the antioxidant profile of 18 species of cyanobacteria (prokaryotic microalgae) and 23 species of (eukaryotic) microalgae is accordingly reported in this paper. The total antioxidant capacity, accounted for by both water- and lipid-soluble antioxidants, was evaluated by the (radical cation) ABTS method. For complementary characterization of cell extracts, a deoxyribose assay was carried out, as well as a bacteriophage P22/Salmonella-mediated approach. The microalga Scenedesmus obliquus strain M2-1 exhibited the highest (p > 0.05) total antioxidant capacity (149 ± 47 AAU) of intracellular extracts. Its scavenger activity correlated well with its protective effects against DNA oxidative damage induced by copper(II)-ascorbic acid; and against decay in bacteriophage infection capacity induced by H2O2. Finally, performance of an Ames test revealed no mutagenic effects of the said extract.
    Marine Drugs 01/2013; 11(4):1256-70. · 3.98 Impact Factor
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    ABSTRACT: This manuscript describes the detailed characterization of edible films made from two different protein products – whey protein isolate (WPI) and whey protein concentrate (WPC), added with three levels of glycerol (Gly) – i.e. 40, 50 and 60%(w/w). The molecular structure, as well as barrier, tensile, thermal, surface and optical properties of said films were determined, in attempts to provide a better understanding of the effects of proteinaceous purity and Gly content of the feedstock. WPI films exhibited statistically lower (p < 0.05) moisture content (MC), film solubility (S), water activity, water vapor permeability (WVP), oxygen and carbon dioxide permeabilities (O2P and CO2P, respectively) and color change values, as well as statistically higher (p < 0.05) density, surface hydrophobicity, mechanical resistance, elasticity, extensibility and transparency values than their WPC counterparts, for the same content of Gly. These results are consistent with data from thermal and FTIR analyses. Furthermore, a significant increase (p < 0.05) was observed in MC, S, WVP, O2P, CO2P, weight loss and extensibility of both protein films when the Gly content increased; whereas a significant decrease (p < 0.05) was observed in thermal features, as well as in mechanical resistance and elasticity – thus leading to weaker films. Therefore, fundamental elucidation was provided on the features of WPI and WPC germane to food packaging – along with suggestions to improve the most critical ones, i.e. extensibility and WVP.
    Food Hydrocolloids 01/2013; 30(1):110–122. · 3.49 Impact Factor
  • 01/2013: pages pg 231-241; , ISBN: 978-1-118-16006-0
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    ABSTRACT: The main purpose of this study was to isolate and briefly characterize proteolytic bacteria from a poorly known habitat – raw wool. Fleece samples were accordingly collected from Merino raw wool – a Portuguese ewe breed, at three distinct areas of their body, from animals exhibiting no symptoms or signs of abnormalities; they were then subjected to enumeration and isolation of a total of 158 bacterial strains. Said isolates were screened for protease activity, using the spot technique, on Calcium Caseinate Agar containing 1% (w/v) skim milk. The 36 isolates displaying the highest protease activity underwent a more refined assessment of enzymatic performance – by examining their cell-free supernatant extracts, using casein as substrate. Two Bacillus isolates were eventually chosen owing to their highest proteolytic activities (24.6 and 15.9 U/mL), and identified using molecular biology tools.
    Small Ruminant Research 01/2013; 109(1):38-46. · 1.12 Impact Factor
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    ABSTRACT: Faster and more selective extraction methods are urged to recover food-grade pigments and antioxidants from microalgae – which do not resort to food-incompatible and environment-unfriendly solvents. Hence, this study ascertained the influence of pressure, temperature, CO2 flow rate and a polar co-solvent upon the yields of carotenoids and chlorophylls in supercritical fluid extraction of Scenedesmus obliquus. The highest carotenoid yield was attained at 250 bar and 60 ºC. The yields of chlorophylls, when using plain CO2, increased slightly with pressure, but decreased with temperature and CO2 flow rate; the highest yield of chlorophyll a was at 4.3 gCO2.min-1, whereas ethanol as co-solvent increased all yields except that of chlorophyll c. The highest ratio of total carotenoids to chlorophyll a was reached at 250 bar and 60 ºC. A remarkable selectivity was observed under these operating conditions, which may enable easy separation and purification of the aforementioned pigments.
    Journal of Food Engineering 01/2013; · 2.28 Impact Factor
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    Ana Catarina Queiroga, Manuela Estevez Pintado, Francisco Xavier Malcata
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    ABSTRACT: The synthesis of an extracellular protease by Bacillus sp. HTS102—a wild strain recently iso-lated from the wool of Portuguese Merino ewes, was optimized. This protease is thermostable and particularly resistant to harsh environmental con-ditions—and appears to bear a unique ability to hydrolyze keratin-rich solid materials. Following a preliminary screening for the most relevant medium factors involved in processing, a frac-tional factorial design (2 VI 6-1) was applied to as-certain the effects of six relevant parameters— viz. yeast extract concentration, peptone level, inoculum size, stirring rate, temperature and pH. The concentrations of yeast extract and peptone, as well as the incubation temperature and pH were found to play significant roles; and the 2-factor interaction between yeast extract level and pH was also significant. A 2.2-fold increase in the overall level of protease synthesis was eventually attained, with the improved medium relative to the basal medium—which is note-worthy when compared with competing prote-ases and previous optimization efforts.
    Natural Science 01/2013; 5(6A):44-53.

Publication Stats

3k Citations
415.47 Total Impact Points

Institutions

  • 2011–2014
    • University of Porto
      Oporto, Porto, Portugal
    • Elsevier B.V.
      Philadelphia, Pennsylvania, United States
  • 2011–2013
    • New University of Lisbon
      • Institute of Chemical and Biological Technology (ITQB)
      Lisboa, Lisbon, Portugal
  • 2010–2013
    • Zagazig University
      • Department of Food Science
      Ez Zaqāzīq, Eastern Province, Egypt
    • Centro de Biotecnologia Agricola e Agro-Alimental do Alentejo
      Beja, Beja, Portugal
  • 1990–2013
    • Universidade Católica Portuguesa
      • Escola Superior de Biotecnologia
      Lisbon, Lisbon, Portugal
  • 2000–2012
    • Instituto Superior da Maia
      Oporto, Porto, Portugal
    • INSTITUTO DE ENGENHARIA MECÂNICA E GESTÃO INDUSTRIAL
      Oporto, Porto, Portugal
  • 2009
    • University of Tehran
      • Department of Food Science and Technology
      Tehrān, Ostan-e Tehran, Iran
  • 2007
    • Universidade Fernando Pessoa
      Oporto, Porto, Portugal
    • Escola Superior Agrária de Coimbra
      Coímbra, Coimbra, Portugal
  • 2004
    • Instituto Politécnico de Viana do Castelo
      • Departamento de Ciências de Engenharia e Tecnologia
      Vianna do Castello, Viana do Castelo, Portugal
  • 1992–1993
    • University of Wisconsin–Madison
      • Department of Chemical and Biological Engineering
      Madison, Wisconsin, United States