F. Xavier Malcata

University of Porto, Oporto, Porto, Portugal

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Publications (462)879.58 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In recent years, microalgae-based carbon-neutral biofuels (i.e., biodiesel) have gained considerable interest due to high growth rate and higher lipid productivity of microalgae during the whole year, delivering continuous biomass production as compared to vegetable-based feedstocks. Therefore, biodiesel was synthesized from three different microalgal species, namely Tetraselmis sp. (Chlorophyta) and Nannochloropsis oculata and Phaeodactylum tricornutum (Heterokontophyta), and the fuel properties of the biodiesel were analytically determined, unlike most studies which rely on estimates based on the lipid profile of the microalgae. These include density, kinematic viscosity, total and free glycerol, and high heating value (HHV), while cetane number (CN) and cold filter plugging point (CFPP) were estimated based on the fatty acid methyl ester profile of the biodiesel samples instead of the lipid profile of the microalgae. Most biodiesel properties abide by the ASTM D6751 and the EN 14214 specifications, although none of the biodiesel samples met the minimum CN or the maximum content of polyunsaturated fatty acids with ≥4 double bonds as required by the EN 14214 reference value. On the other hand, bomb calorimetric experiments revealed that the heat of combustion of all samples was on the upper limit expected for biodiesel fuels, actually being close to that of petrodiesel. Post-production processing may overcome the aforementioned limitations, enabling the production of biodiesel with high HHV obtained from lipids present in these microalgae
    Journal of Applied Phycology 08/2015; DOI:10.1007/s10811-015-0683-5 · 2.49 Impact Factor
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    ABSTRACT: Whey proteins are widely used as nutritional and functional ingredients in formulated foods because they are relative inexpensive, generally recognized as safe (GRAS) ingredient and possess important biological, physical and chemical functionalities. Denaturation and aggregation behavior of these proteins is of particular relevance toward manufacture of novel nanostructures with a number of potential uses. When these processes are properly engineered and controlled, whey proteins may be formed into nanohydrogels, nanofibrils or nanotubes and be used as carrier of bioactive compounds. This review intends to discuss the latest understandings of nanoscale phenomena of whey protein denaturation and aggregation that may contribute for the design of protein nanostructures. Whey protein aggregation and gelation pathways under different processing and environmental conditions such as microwave heating, high voltage and moderate electrical fields, high pressure, temperature, pH and ionic strength were critically assessed. Moreover, several potential applications of nanohydrogels, nanofibrils and nanotubes for controlled release of nutraceutical compounds (e.g. probiotics, vitamins, antioxidants and peptides) were also included. Controlling the size of protein networks at nanoscale through application of different processing and environmental conditions can open perspectives for development of nanostructures with new or improved functionalities for incorporation and release of nutraceuticals in food matrices.
    Critical reviews in food science and nutrition 06/2015; DOI:10.1080/10408398.2014.993749 · 5.55 Impact Factor
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    ABSTRACT: Use of probiotic bacteria and consumes in large – in novel foods to provide beneficial health effects has attracted an increasing interest by the food industry and fermented olives are an excellent example of a new generation of those foods from plant origin so as to assure maximum viability by the time of ingestion during processing and storage of food products, as well as during transit through the gastrointestinal tract.
    Food Research International 05/2015; 75. DOI:10.1016/j.foodres.2015.04.048 · 3.05 Impact Factor
  • Mohamed Abdel Hamid Rabie · Ali A. Abdel Galeel · Francisco Xavier Malcata
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    ABSTRACT: Edam-type curd slurry inoculated with 1% Lactococcus lactis subsp. lactis KF147 as control and further added with Propionibacterium shermanii PS-4 + Bifidobacterium bifidum DSM 20082 (1:1), P. shermanii PS-4 + Lactobacillus acidophilus ATCC4356 or P. shermanii PS-4 + B. bifidum DSM 20082 + Lactobacillus acidophilus ATCC4356 (1:1:1), at a rate of 1%, were studied for their effect upon biogenic amine and proteolysis pattern during incubation at 30C for 21 days. Results showed no significant influence of any combination of probiotic microorganisms on total solids, salt and fat of Edam-type curd slurries, but some effect on pH and soluble nitrogen fractions; presence of P. shermanii + B. bifidum + Lactobacillus acidophilus led to the highest concentration (7.9%) of water-soluble nitrogen by the end of incubation. When inoculation included B. bifidum, a significant decrease in total biogenic amines (from 447 to 37 mg/kgDW) was observed by 21 days – with histamine decreasing from 84 to 25 and tyramine from 359 to 6 mg/kgDW.Practical ApplicationsThis study was aimed at investigating proteolysis and biogenic amine formation by selected probiotic bacteria added to Edam-type curd slurry. The nitrogen fractions and biogenic amines in control increased significantly throughout incubation at 30C. Inocula of P. shermanii + L. acidophilus + B. bifidum (1:1:1) could effectively reduce biogenic amine contents, especially histamine and tyramine. This observation has potential public health impact because regular curds are often above the maximum legal threshold in regions with warm weather and poor cold storage network. Furthermore, addition of probiotic L. acidophilus and B. bifidum improved the overall flavor profile, owing to extra soluble nitrogen produced.
    Journal of Food Processing and Preservation 04/2015; DOI:10.1111/jfpp.12475 · 0.94 Impact Factor
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    ABSTRACT: Yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson; Asteraceae] roots have been shown to be a source of prebiotic compounds. However, there are no known studies concerning processed yacon roots. The objective of this study was to investigate the potential prebiotic activity of yacon tuber flour. For this purpose, an aqueous extract was tested for selection of yacon incorporation and sterilization method and selection of the most favourable concentration to be tested for prebiotic activity. Once these conditions were identified, the potential prebiotic activity of the yacon extract was evaluated by determination of viable cell numbers and metabolic activity against four probiotic strains, namely, Enterococcus faecium 32, Bifidobacterium animalis Bo, Lactobacillus acidophilus Ki and Lactobacillus casei L26). Results showed that the best incorporation and sterilization method was to autoclave the supernatant, resultant from the yacon tuber flour suspension, at 121 °C for 20 min and add it to sterilized basal medium. For the confirmation of potential prebiotic activity, de Man-Rogosa-Sharpe (MRS) medium without a conventional carbon source (negative control), with 2% (w/v) glucose per se (positive control) and associated with 1% (w/v) yacon tuber flour were chosen. Yacon tuber flour revealed a potential prebiotic activity upon the growth of the probiotic strains tested, probably due to its fructooligosaccharides (FOS) content.
    Food and Bioproducts Processing 04/2015; 95. DOI:10.1016/j.fbp.2015.04.003 · 2.29 Impact Factor
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    ABSTRACT: The objective of this research work was to investigate the antioxidant properties of sterilized yacon tuber flour. The results revealed for the first time the high antioxidant activity of sterilized yacon flour. The best extract obtained by boiling 8.9% (w/v) of yacon flour in deionised water for 10min exhibited a total antioxidant capacity of 222±2mg (ascorbic acid equivalent)/100g DW and a total polyphenol content of 275±3mg (gallic acid equivalent)/100g DW associated to the presence of four main phenolic compounds: chlorogenic acid, caffeic acid, coumaric acid and protocatechuic acid, as well as the amino acid tryptophan. The most abundant was chlorogenic acid, followed by caffeic acid. Biological assays revealed that the extract had indeed antioxidant protection, and no pro-oxidant activity. In conclusion, sterilized yacon tuber flour has the potential to be used in the food industry as a food ingredient to produce functional food products. Copyright © 2015. Published by Elsevier Ltd.
    Food Chemistry 04/2015; 188. DOI:10.1016/j.foodchem.2015.04.047 · 3.39 Impact Factor
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    ABSTRACT: Proteins are one of the food constituents most affected by heating, and some of the changes involve their unfolding, denaturation and gelation. Ohmic heating has often been claimed to improve the quality of foodstuffs due to its uniform heating and (putative) presence of a moderate electric field (MEF). However, this is still subject to discussion, so it is important to determine the effect of ohmic heating and of its MEF upon food constituents. Hence, the aim of this work was to evaluate the effects of MEF on denaturation, aggregation and viscoelastic properties of whey protein isolate (WPI), and compare them with those obtained via conventional heating under identical treatment conditions (up to 30 min at 85 °C). Results have shown that MEF interferes with whey protein unfolding and aggregation pathways at relatively high temperatures. MEF treatments have resulted in WPI solutions possessing more 8 and 10% of native β-Lactoglobulin and α-Lactalbumin, respectively, after 30 s of heating at 85 °C, when compared with a conventional heating method. Protein aggregates from MEF-treated WPI solutions presented a maximum increase in size of 78 nm, whereas conventional heating produced an increase of 86 nm. Unlike in conventional heating, aggregation of whey proteins during MEF was not sufficiently strong to form a true elastic gel network, since decreases in both storage and loss modulus were observed following MEF treatment. Our results suggest that MEF may provide a novel method for production of a whey protein matrix with distinctive gel-forming properties.
    Food Hydrocolloids 01/2015; 43:329-339. DOI:10.1016/j.foodhyd.2014.06.002 · 4.28 Impact Factor
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    ABSTRACT: The research effort described here has focused on incorporation of Lactobacillus casei, in whey protein matrices, in the presence of selected salty additives. Those matrices were produced via thermal processing of a combination of either ovine or bovine whey (or a mixture thereof) with ovine milk, and were inoculated (at 10%) with L. casei strain LAFTI®L26; salt, salt and herbs, or salt and xanthan were further added to such matrices, which were then homogenized and stored at 7 °C for up to 21 d. In general, viable cell numbers maintained or even increased throughout the storage period, irrespective of the type of salty additive considered. Partial depletion of lactose was detected, and concomitant production of lactic acid throughout the 21 d-period of storage; lower lactic acid concentrations were found in matrices containing salty additives. In matrices with xanthan (SX), the probiotic strain exhibited the lowest metabolic activity. Matrices SX were less soft and firmer than the others, by the end of storage, and were similar to matrices with herbs (SH). The incorporation of salty additives affected bacterial metabolism, in terms of glycolysis and proteolysis, which in turn had a significant impact on the development of textural properties.
    Food Bioscience 01/2015; 10. DOI:10.1016/j.fbio.2015.01.004
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    ABSTRACT: This work presents the first study on the bacterial communities in Pico cheese, a traditional cheese of the Azores (Portugal), made from raw cow's milk. Pyrosequencing of tagged amplicons of the V3–V4 regions of the 16S rDNA and Operational Taxonomic Unit-based (OTU-based) analysis were applied to obtain an overall idea of the microbiota in Pico cheese and to elucidate possible differences between cheese-makers (A, B and C) and maturation times. Pyrosequencing revealed a high bacterial diversity in Pico cheese. Four phyla (Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes) and 54 genera were identified. The predominant genus was Lactococcus (77% of the sequences). Sequences belonging to major cheese-borne pathogens were not found. Staphylococcus accounted for 0.5% of the sequences. Significant differences in bacterial community composition were observed between cheese-maker B and the other two units that participated in the study. However, OTU analysis identified a set of taxa (Lactococcus, Streptococcus, Acinetobacter, Enterococcus, Lactobacillus, Staphylococcus, Rothia, Pantoea and unclassified genera belonging to the Enterobacteriaceae family) that would represent the core components of artisanal Pico cheese microbiota. A diverse bacterial community was present at early maturation, with an increase in the number of phylotypes up to 2 weeks, followed by a decrease at the end of ripening. The most remarkable trend in abundance patterns throughout ripening was an increase in the number of sequences belonging to the Lactobacillus genus, with a concomitant decrease in Acinetobacter, and Stenotrophomonas. Microbial rank abundance curves showed that Pico cheese's bacterial communities are characterized by a few dominant taxa and many low-abundance, highly diverse taxa that integrate the so-called “rare biosphere”.
    International Journal of Food Microbiology 01/2015; 192:86-94. DOI:10.1016/j.ijfoodmicro.2014.09.031 · 3.16 Impact Factor
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    ABSTRACT: The development of bio-based nanostructures as nanocarriers of bioactive compounds to specific body sites has been presented as a hot topic in food, pharmaceutical and nanotechnology fields. Food and pharmaceutical industries seek to explore the huge potential of these nanostructures, once they can be entirely composed of biocompatible and non-toxic materials. At the same time, they allow the incorporation of lipophilic and hydrophilic bioactive compounds protecting them against degradation, maintaining its active and functional performance. Nevertheless, the physicochemical properties of such structures (e.g., size and charge) could change significantly their behavior in the gastrointestinal (GI) tract. The main challenges in the development of these nanostructures are the proper characterization and understanding of the processes occurring at their surface, when in contact with living systems. This is crucial to understand their delivery and absorption behavior as well as to recognize potential toxicological effects. This review will provide an insight into the recent innovations and challenges in the field of delivery via GI tract using bio-based nanostructures. Also, an overview of the approaches followed to ensure an effective deliver (e.g., avoiding physiological barriers) and to enhance stability and absorptive intestinal uptake of bioactive compounds will be provided. Information about nanostructures’ potential toxicity and a concise description of the in vitro and in vivo toxicity studies will also be given.
    Food Engineering Reviews 01/2015; DOI:10.1007/s12393-015-9116-0 · 3.04 Impact Factor
  • J Marcelino Kongo · F Xavier Malcata
    01/2015; Elsevier.
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    ABSTRACT: Production of edible nanostructures constitutes a major challenge in food nanotechnology, and has attracted a great deal of interest from several research fields - including (but not limited to) food packaging. Furthermore, whey proteins are increasingly used as nutritional and functional ingredients owing to their important biological, physical and chemical functionalities. Besides their technological and functional characteristics, whey proteins are generally recognized as safe (GRAS). Denaturation and aggregation kinetics behavior of such proteins are of particular relevance toward manufacture of novel nanostructures possessing a number of potential uses. When these processes are properly engineered and controlled, whey proteins may form nanostructures useful as carriers of bioactive compounds (e.g. antimicrobials, antioxidants and nutraceuticals). This review discusses the latest advances in nano-scale phenomena involved in protein thermal aggregation aiming at formation of bio-based nano-coating networks. The extent of aggregation is dependent upon a balance between molecular interactions and environmental factors; therefore, the impact of these conditions is addressed in a critical manner. A particular emphasis is given to the effect of temperature as long as being one of the most critical variables. The application of moderate electric fields (MEF), an emergent approach, as such or combined with conventional heating is considered as it may inhibit/prevent excessive denaturation and aggregation of whey proteins - thus opening new perspectives for development of innovative protein nanostructures (i.e. nano-coatings). A better understanding of the mechanism(s) involved in whey protein denaturation and aggregation is crucial as it conveys information relevant to select methods for manipulating interactions between molecules, and thus control their functional properties in tailor-made applications in the food industry.
    Food Research International 12/2014; 66:344-355. DOI:10.1016/j.foodres.2014.09.036 · 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.
    Lebensmittel-Wissenschaft und-Technologie 11/2014; 59(1):234–246. DOI:10.1016/j.lwt.2014.03.003 · 2.47 Impact Factor
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  • Câmara SP · Dapkevicius MLNE · Silva CCG · Malcata FX
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    ABSTRACT: Enterococci are part of the dominant flora in traditionally fermented cheeses made with raw milk and play a relevant role in the development of the organoleptic characteristics of the final product. Because of their role in ripening, flavour development and bacteriocin production in cheeses, it has been suggested that Enterococci with desirable technological and metabolic traits could be included in starter cultures for various cheeses. However, the Enterococcus genus is not regarded as GRAS and safety concerns may be raised for certain strains. The aim of the present work was to characterise 27 strains Enterococcus faecalis isolated from Pico cheese with emphasis on those aspects of greater concern such as the incidence of virulence factors, antibiotic resistance traits and production of biogenic amines. PCR reactions were used to detect the presence of genes involved in the expression of gelatinase (gelE), hyaluronidase (hyl), aggregation substance (asa1), enterococcal surface protein (esp), cytolysin (cylA), endocarditis antigen (efaA), collagen adhesion (ace), vancomycin resistance (vanA and vanB), aminoglycoside resistance [aac(6’)-Ie-aph(2’)-Ia, aph(2’)-Ib, aph(2’)-Ic, aph(2’)-Id, aph(3’)-IIIa, and ant(4’)-Ia], histidine decarboxylase (hdc1 and hdc2), tyrosine decarboxylase (tdc), and ornithine decarboxylase (odc). None of the tested strains carried vancomycin resistance genes. In the case of aminoglycosides, 8 isolates tested positive for just one of the six resistance genes tested. The most prevalent virulence genes were efaA, gelE and ace. The tdc gene was also common in the tested strains. All of the tested isolates were efaA positive. The prevalence of virulence genes may be a hurdle when considering their application as starter cultures. E098
    11th International Symposium on Lactic Acid Bacteria: HEALTH, SUSTAINABILITY, DIVERSITY, AND APPLICATION, Egmond an Zee, The Netherlands; 08/2014
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    ABSTRACT: Enterococci are part of the dominant flora in traditionally fermented cheeses made with raw milk and play a relevant role in the development of the organoleptic characteristics of the final product. Because of their role in ripening, flavour development and bacteriocin production in cheeses, it has been suggested that Enterococci with desirable technological and metabolic traits could be included in starter cultures for various cheeses. However, the Enterococcus genus is not regarded as GRAS and safety concerns may be raised for certain strains. The aim of the present work was to characterise 27 strains Enterococcus faecalis isolated from Pico cheese with emphasis on those aspects of greater concern such as the incidence of virulence factors, antibiotic resistance traits and production of biogenic amines. PCR reactions were used to detect the presence of genes involved in the expression of gelatinase (gelE), hyaluronidase (hyl), aggregation substance (asa1), enterococcal surface protein (esp), cytolysin (cylA), endocarditis antigen (efaA), collagen adhesion (ace), vancomycin resistance (vanA and vanB), aminoglycoside resistance [aac(6’)-Ie-aph(2’)-Ia, aph(2’)-Ib, aph(2’)-Ic, aph(2’)-Id, aph(3’)-IIIa, and ant(4’)-Ia], histidine decarboxylase (hdc1 and hdc2), tyrosine decarboxylase (tdc), and ornithine decarboxylase (odc). None of the tested strains carried vancomycin resistance genes. In the case of aminoglycosides, 8 isolates tested positive for just one of the six resistance genes tested. The most prevalent virulence genes were efaA, gelE and ace. The tdc gene was also common in the tested strains. All of the tested isolates were efaA positive. The prevalence of virulence genes may be a hurdle when considering their application as starter cultures. Poster E098
    11th International Symposium on Lactic Acid Bacteria: HEALTH, SUSTAINABILITY, DIVERSITY, AND APPLICATION, Egmond an Zee, The Netherlands; 08/2014
  • Encyclopedia of food and health Aims & Scope, Edited by Caballero B., Finglas P., Toldra F., 08/2014: chapter Whey and whey powders, production and uses; Elsevier Science.
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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.
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    Freni K Tavaria · Eduardo M Costa · Eduardo J Gens · Francisco Xavier Malcata · Manuela E Pintado
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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. DOI:10.1111/1346-8138.12315 · 2.35 Impact Factor

Publication Stats

8k Citations
879.58 Total Impact Points

Institutions

  • 2002–2015
    • University of Porto
      • Laboratory for Process, Environmental and Energy Engineering
      Oporto, Porto, Portugal
  • 1987–2015
    • Universidade Católica Portuguesa
      • • Escola Superior de Biotecnologia
      • • Centro de Biotecnologia e Química Fina
      Lisboa, Lisbon, Portugal
  • 2011–2013
    • University of Aveiro
      Aveiro, Aveiro, Portugal
    • Elsevier B.V.
      Philadelphia, Pennsylvania, United States
  • 2010–2013
    • New University of Lisbon
      • Institute of Chemical and Biological Technology (ITQB)
      Lisboa, Lisbon, Portugal
    • Centro de Biotecnologia Agricola e Agro-Alimental do Alentejo
      Beja, Beja, Portugal
  • 2010–2012
    • Instituto Superior da Maia
      Oporto, Porto, Portugal
  • 2006–2007
    • Escola Superior Artística do Porto
      Oporto, Porto, Portugal
  • 1990–1993
    • University of Wisconsin–Madison
      • Department of Chemical and Biological Engineering
      Madison, Wisconsin, United States