Browsing by Author "Macedo, A. C."
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- Assessment of proteolysis and lipolysis in Serra cheese: effects of axial cheese location, ripening time and lactation seasonPublication . Macedo, A. C.; Costa, M. L.; Malcata, F. X.The degrees of proteolysis and Iipolysis in Serra cheese were measured in cheese samples obtained from experiments laid out as a three-way facto rial design replicated twice. The independent variables studied were the location within the cheese (from the center to the surface), the position in the lactation season (from October to June) and the ripening time (from 0 to 35 days). Ali three variables had statistically significant effects on the concentration of water soluble peptides (WSP), but only the ripening time and the period within the lactation season affected the fat acidity (FA). The extents (alter the given ripening period) and the rates (averaged over the ripening period) of generation of WSP and FA were highest for spring and lowest for autumn. The lowest values for both the proteolysis extent and the proteolysis rate were obtained for the rind. The rates of proteolysis and lipolysis tended to decrease with ripening time; most of the lipolysis occurred during the first week, but proteolysis was still in progress by 35 days of ripening.
- Hydrolysis of αs- and β-caseins during ripening of Serra cheesePublication . Macedo, A. C.; F. X., MalcataHydrolysis of the major caseins in Serra cheese manufactured from raw sheep's milk coagulated with a plant rennet (Cynara cardunculus, L.) was monitored by urea-PAGE electrophoresis throughout a 35 day ripening period (with sampling at 0, 7, 21 and 35 days) and throughout the cheesemaking season (with sampling at November, February and May). The αs- and β-caseins were degraded up to 82 and 76%, respectively, by 35 days of ripening. The αs-casein variants (αs2- and αs3-) displayed similar degradation patterns to one another, but different from those of β-casein variants (β1- and β2-). Although the αs-caseins were broken down more slowly than β-caseins at early stages of ripening (97, 95, 80, and 60% of αs2-, αs3-, β1-, and β2-caseins, respectively, were still intact by 7 days), this observation was reversed for later stages of ripening (18, 18, 30, and 20% of αs2-, αs3-, β1− and β2-caseins, respectively, were still intact by 35 days of ripening). The position along the cheese-making season significantly affected the hydrolysis of only the β2- and αs3-caseins. Degradation of αs3-casein was slower in February than in November or May for 21-day old cheeses; cheeses ripened for 7 days or 21 days showed more intact β2-casein when manufactured in May than in November or February. The magnitude of the correlation coefficients pertaining to concentrations of intact αs- and β-caseins indicated that the products of proteolytic breakdown with higher mobility than αs-caseins (tentatively termed α1-I, α2-I, and α3-I) were preferentially correlated with αs-caseins, the products of proteolytic breakdown with mobility between β-caseins and αs-caseins (tentatively termed β1 and β1-I) were preferentially correlated with β1 and β2-caseins rather than with αs-caseins, and the products of proteolytic breakdown with the highest mobility (tentatively termed α/β1-II and α/β2-II) were preferentially correlated with β-caseins.
- Microbiological profile in Serra ewes' cheese during ripeningPublication . Macedo, A. C.; Malcata, F. X.; Hogg, T. A.The microflora of Serra cheese was monitored during a 35 d ripening period at three different periods within the ewe's lactation season. After 7 d ripening, the numbers of micro-organisms reached their maximum, and lactic acid bacteria (LAB) and coliforms were the predominant groups. Pseudomonads were not detected after 1 week of ripening. At all stages of ripening, cheeses manufactured in spring exhibited the lowest numbers of LAB and yeasts, whereas cheeses manufactured in winter showed the lowest numbers of coliforms and staphylococci. Leuconostoc lactis was the most abundant LAB found in Serra cheese whereas Enterococcus faecium and Lactococcus lactis spp. lactis exhibited the highest decrease in percentage composition. Numbers of both Leuc. mesenteroides and Lactobacillus paracasei tended to increase throughout ripening. The most abundant coliform was Hafnia alvei. Klebsiella oxytoca was found in curd but declined in number during ripening. Staphylococcal flora of curd was mainly composed of Staphylococcus xylosus, Staph. aureus and Staph. epidermidis. Staphylococcus xylosus was the major species found at the end of ripening. Pseudomonas fluorescens, was the only Pseudomonas species isolated from the curd. Although a broad spectrum of yeasts were found in Serra cheese, Sporobolomyces roseus was the most abundant yeast isolated.
- Review: Steam distilled spirits from fermented grape pomace Revision: Bebidas destiladas obtenidas de la fermentación del orujo de uvaPublication . Silva, M. L.; Macedo, A. C.; Malcata, F. X.Grape pomace is the solid residue left after juice extraction from grapes, and represents in Mediterra nean countries the most important by-product of the winemaking industry. Steam distillation of fer mented grape pomace will eventually produce a spirit, designated as bagaceira in Portugal, orujo in Spain and grappa in Italy. This paper comprehensively reviews fundamental and applied aspects of the manufacture of these spirits, encompassing their composition as well as metabolic reactions and microbial ecology that determine such composition during fermentation. These spirits adhere to maxi mum levels of methanol (potential toxic compound) and 2-butanol (potential flavor defect) fixed by EC regulations. Available studies pertaining to bagaceira, orujo and grappa have indicated that the final quality of these spirits depends strongly on the quality of the fresh grapes, the storage condi tions, and the distillation equipment and procedure employed.
- Review: Technological and organoleptic issues pertaining to cheeses with denomination of origin manufactured in the Iberian Peninsula from ovine and caprine milksPublication . Freitas, A.C; Macedo, A. C.; Malcata, F. X.A few European countries have created Appélations d'Origine Protegée (AOP) in order to support legal protection and hence promote enforcement of high-quality standards of selected food products. This paper comprehensively reviews and updates fundamental and applied aspects encompassing tech nological and organoleptic characteristics of AOP traditional cheeses manufactured in the Iberian Peninsula, from ovine and/or caprine milks. Those cheeses from Portugal and Spain can be divided into four distinctive groups, based on milk source and rennet type: (i) Azeitão, Castelo Branco, Évora, Nisa, Serpa, Serra da Estrela and La Serena cheeses, manufactured with raw ovine milk and coagulated via plant rennet; (ii) Terrincho, Idiazábal, Manchego, Roncal and Zamorano cheeses, elaborated with raw ovine milk and coagulated via animal rennet; (iii) Cabra Transmontano and Majorero cheeses, manufac tured with raw caprine milk and coagulated via animal rennet; and (iv) Amarelo da Beira Baixa, Picante da Beira Baixa and Rabaçal cheeses, manufactured with mixtures of raw ovine and caprine milks and coagulated via animal rennet. Considerable differences between Portuguese and Spanish AOP cheeses exist; the former are, in general, characterized by softer consistencies and similarities to one another in terms of manufacturing protocols (usually encompassing coagulation of plain raw milk followed by slow draining of the curd), whereas the latter are, in general, larger and firmer.
- Review: Technology, Chemistry and Microbiology of Whey CheesesPublication . Pintado, M. E.; Macedo, A. C.; Malcata, F. X.In whey cheese manufacture, whey, plain or added with milk, is heated by direct fire, bubbling steam or alternatively in jacketed vats. In some cases, salt s or organic acids are previously added. At 80-85 OC, the first particles of curd form; at 85-95 'C, the curd may be cooked for a few minutes to reduce moisture content and/or to obtain the desirable level of browning. After drainage at room temperature during molding for ca. 4 h, whey cheese is stored at ca. 4 'C. The typical mass yield is 6%, but addition of milk, calcium salts and preliminary concentration of protein (by condensation or ultrafiltration techniques) may increase yield considerably. Some types of whey cheeses are supposed to be consumed within a short time upon manufacture (e.g., Ricotta, Requeijdo and Manouri), whereas others bear a longer shelf life (e.g., Gjetost, Mysost and Myzithra). Whey cheeses are significantly different from one another in terms of chemical composition, which is mainly due to variations in the source and type of whey, as well as to the processing practices followed. Moisture content and pH of whey cheeses are usually high and favor microorganism growth (molds, yeasts, lactic acid bacteria and Enterobacteriaceae account for the dominant microflora in these cheeses). Adequate packaging of whey cheeses should be provided, and legislation should be prepared to fix standard characteristics of each type of whey cheese, and hence protect typical products from adulteration and fakes. Marketing efforts should also be aimed at increasing whey cheese consumption, either directly or incorporated in desserts, snack dips and pasta-type dishes.
- The microstructure and distribution of micro-organisms within mature Serra cheesePublication . Parker, M. L.; Gunning, P. A.; Macedo, A. C.; Malcata, F. X.; Brocklehurst, T. F.The distribution of micro-organisms in mature Serra, a traditional Portuguese cheese made from unpasteurised ewes’ milk without added starter culture, was examined by light microscopy and electron microscopy. Four populations of micro-organisms were recognized according to their position within the cheese: (i) those present as apparently axenic colonies within the curd matrix; (ii) bacteria growing along curd junctions; (iii) yeasts and bacteria present in the smear on the surface of the cheese and (iv) bacteria found in cracks which penetrated the outer part of the cheese from the rind. Two types of crystals were observed, together with contaminants of vegetable origin and somatic cells originating from the milk.