Influence of the Coagulant Level on Early Proteolysis in Ovine Cheese-like Systems Made with Sterilized Milk and Cynara cardunculus |
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Authors: | SV Silva FX Malcate |
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Affiliation: | Authors Silva and Malcata are with the Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200–072 Porto, Portugal. Direct inquiries to author Malcata (E-mail: ). |
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Abstract: | ABSTRACT: The effect of coagulant level on the quality and quantity of protein breakdown during the first 24 h of ripening of cheese-like systems, manufactured with sterilized ovine milk using crude aqueous extracts of Cynara cardunculus as coagulant, was experimentally assessed. Urea-polyacrylamide gel electrophoresis was performed on both water-soluble and water-insoluble cheese extracts to monitor the casein degradation pattern; the ripening extension index and the ripening depth index were thus calculated. Peptides from the water-soluble fraction were isolated by reverse-phase, high-performance liquid chromatography and partially sequenced by Edman degradation. Higher residual coagulant levels in curdled milk led to earlier breakdown of caseins, as expected. The primary cleavage sites were Phe105-Met106 in k-casein, Phe23-Val24 in αs1-casein, and Leu127-Thr128, Ser142-Trp143, Leu165-Ser166, and Leu190-Tyr191 in β-casein. |
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Keywords: | plant rennet ripening dairy food HPLC electrophoresis |
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