Percorrer por autor "Sousa, M. José"
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- Degradation of caseins from milk of different species by extracts of Centaurea calcitrapaPublication . Tavaria, Freni K.; Sousa, M. José; Domingos, Ana; Malcata, F. Xavier; Brodelius, Peter; Clemente, Alda; Pais, M. SaloméTwo purified aqueous extracts of Centaurea calcitrapa, a plant from the Compositae family, were shown to degrade bovine, ovine, and caprine milk caseinates. The corresponding hydrolysis patterns were monitored by urea-polyacrylamide gel electrophoresis and compared with those of a commercial mixture of chymosin and pepsin. The plant proteases degraded both Rs- and â-caseins more extensively than the commercial rennet, thus yielding proteolytic patterns where different specificities toward such substrates are apparent. The animal rennet was found to display the greatest clotting power per milligram of protein but the least specificity toward ovine and caprine caseins. It is, therefore, suggested that the said plant extracts be used as an alternative to commercial animal rennets especially in the manufacture of caprine and ovine milk cheeses.
- Effect of storage and lyophilization on ovine and caprine casein degradation by extracts of Cynara cardunculus (L.)Publication . Tavaria, Freni K.; Sousa, M. José; Malcata, F. Xavier
- Evolution of free fatty acid profile during ripening in cheeses manufactured from bovine, ovine and caprine milks with extracts of Cynara cardunculus as coagulantPublication . Sousa, M. José; Balcão, Victor M.; Malcata, F. XavierChanges in the concentrations of free fatty acids (FFA) in bovine, ovine and caprine milk cheeses manufactured with a plant rennet (flowers of Cynara cardunculus) were studied throughout a 68-day ripening period. The long-chain saturated (C16 : 0 and C18 : 0) and unsaturated (C18 : 1, C18 : 2, and C18 : 3) FFA were the most abundant at all stages of ripening. The overall concentration of FFA in fresh cheese was 3598, 3538 and 3868 mg/kg cheese for bovine, ovine and caprine milk cheeses, respectively; these values increased to 5047, 6517 and 5257 mg/kg cheese, respectively, by 68 days, of which 1171, 1734 and 1791 mg/kg cheese, respectively, were accounted for by C4 : 0 – C12 : 0. The FFA that showed the highest fractional increase by 68 days of ripening in bovine milk cheese were C4 : 0, C6 : 0, C8 : 0, C12 : 0, C18 : 1 and C18 : 2; in ovine milk cheese they were C4 : 0, C6 : 0, C8 : 0, C10 : 0, C14 : 0, and C18 : 1; and in caprine milk cheese they were C4 : 0, C8 : 0, C10 : 0, C14 : 0 and C18 : 1.
- Perspectivas científico-tecnológicas na caracterização de melhoramento do Queijo da Serra da EstrelaPublication . Malcata, F. Xavier; Macedo, Ângela C.; Sousa, M. JoséNo intuito de permitir um melhor conhecimento de índole científico-tecnológica sobre o Queijo Serra da Estrela, foi desenvolvido trabalho experimental em duas vertentes principais, a saber caracterização do processo de maturação e melhoramento do processo de fabrico. Tais vertentes abrangem tentativas de descrição de fenómenos de lipólise, proteólise e glicose, bem como tentativas de estabelecimento de relações causa/efeito entre varias tecnologias e as características do produto final, numa perspectiva de racionalização do papel dos diversos microorganismos nativos e do coalho no processo de manufactura do queijo.
- Proteolysis of ovine and caprine Caseins in solution by enzymatic extracts from flowers of Cynara cardunculusoPublication . Sousa, M. José; Malcata, F. XavierPrimary proteolysis of ovine and caprine Na-caseinate at 30°C in phosphate buffer at pH 6.5 or 5.5 in the absence of NaCl and at pH 5.2 with 5% (w/v) NaCl by cardosins in aqueous extracts of Cynara cardunculus flowers was investigated using urea-polyacrylamide gel electrophoresis and reversed-phase high performance liquid chromatography. Caprine caseinate underwent more extensive degradation than ovine caseinate under the same conditions (pH 6.5 and pH 5.5); proteolysis of b- and as-caseins in ovine and, to a lesser extent, in caprine caseinates was reduced in the presence of 5% (w/v) NaCl. Peptide profiles of the pH 4.6-soluble extract had different patterns throughout ripening arising from the different specificity of cardosins toward ovine and caprine Na-caseinates. The major cleavage sites in ovine (caprine) caseinate were Phe105-Met106 (Lys116-Thr117) for k-casein, Leu127-Thr128 and Leu190-Tyr191 (Glu100-Thr101, Leu127-Thr128, Leu136-Pro137 and Leu190- Tyr191) for b-casein, Phe23-Val24 (Phe23-Val24, Trp164-Tyr165 and Tyr173-Thr174) for as1-casein and Phe88-Tyr89 (Ser9-Ser10, Phe88-Tyr89 and Tyr179-Leu180) for as2-casein.
- Storage and lyophilization effects of extracts of Cynara cardunculus on the degradation of ovine and caprine caseinsPublication . Tavaria, Freni K.; Sousa, M. José; Malcata, F. XavierClotting and proteolytic activities are important parameters when evaluating rennets for cheesemaking. Both these activities were determined for extracts of the plant Cynara cardunculus in fresh form and after lyophilization followed by reconstitution, either in water or in citrate buffer (pH 5.4) and stored for up to 4 weeks at 4°C. The patterns of degradation of ovine and caprine caseins were followed by urea polyacrylamide gel electrophoresis in attempts to qualitatively differentiate the activity of the enzyme extracts as storage time elapsed. Storage at 4°C significantly decreased the clotting power of the extracts but lyophilization retarded this decrease; β- and αs-casein breakdown generally increased with storage time, via patterns that depend on caseinate type and extract used, but lyophilized extracts reconstituted in citrate buffer were significantly less proteolytic than the other extracts. Therefore, it is suggested that lyophilized extracts (reconstituted with citrate buffer) of flowers of C. cardunculus be used rather than fresh extracts.