Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.15/118
Título: The mechanism of action of polyphosphates
Autor: Raimundo, António
Palavras-chave: meat
Data de Defesa: 1990
Resumo: Polyphosphates in small concentrations allow the use of lower concentrations of salt in the manufacture of meat products reducing their salty taste and the health risk from over-consumption of sodium. In their presence a better bind is achieved and the water present in the raw meat or takin up during processing is retained more completely after cooking. The aim of this thesis was to study the molecular mechanism by which polyphosphates funtion. Rabbit myofibrils and mince were used to investigate the effect of pyrophosphate on swelling and protein extraction in a range of NaCl concentrations from 0.1-1.0 M at pH6.0. 1mM pyrophosphate had little effect on thee swelling of myofibrils in 0.1 to 0.4 M NaCl but, at higher NaCl concentrations it caused a marked inhibition of swelling. In the presence of 10 mM pyrophosphate swelling was higher than in NaCl alone in 0.3 and 0.4 M NaCl, but again at higher NaCl concentrations pyrophosphate caused a marked inhibition of swelling. Protein extration was higher at NaCl concentrations above 0.2 M in the presence of 10 mM pyrophosphate. Phase-contrast light micrographs showed pyrophosphate to extract the A-band as the NaCl concentration rose to 0.3 M NaCl and above, and in NaCl alone concentrations of 0.4 M and above only images of a disordered myofibrillar structure were observed. The results of Bendall(1954) that phyrophosphate increases the water uptake of mince were confirmed. In mince washed to remove endogenous ions and sarcoplasmic proteins, 10mM phyrophosphate produced more swelling and extraction of protein than NaCl alone were produced in the 0.1-0.3 M NaCl concentration range but, at higher concentrations it produced inhibition of swelling. However, swelling in washed mince was mince was less than in myofibrils under the same ionic conditions. The results are interpreted by supposing that phyrophosphate promotes the dissociation of actomyosin, changing the myofibrils from a rigor to a relaxed state allowing limited expansion of the filament lattice. In NaCl concentrations above 0.3M phyrophosphate is also thought to co-operate with salt to depolymerise the thick filament allowing myosin to be extracted and causing a depression of swelling.
Descrição: Dissertation submitted to the University of Bristol in partial fulfilment of the degree of Master of Science in Meat Science by Advanced Study and Research - Institute of Food Research, Bristol laboratory (Langford)
URI: http://hdl.handle.net/10400.15/118
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