The protective effect of amino acid and joint protective effects of various mixtures, which included sorbitol, sucrose, Na-Glu, Na-Asp, or Gly, on the thermal stability of chub mackerel myofibrils have been studied. The first order rate constant (
kD) for inactivation of myofibrillar Ca-ATPase was determined in each case.
Plotting the logarithm of
kD against the concentration (M) of amino acid, a single linear relation was obtained for Gly, Ala, and β-Ala, whereas a linear relation with two steps was found for Na-Glu and Na-Asp. The slope (
E) of the graph of log
kD versus molarity of amino acid revealed that the protective effect against the denaturation of myofibrils becomes lowerin the order of: Na-Glu (0-0.75M), Na-Asp (0-0.75M), Gly=Ala=β-Ala (0-1.5M), Na-Glu (0.75-2.5M), Na-Asp (0.75-2.5M), Pro (0-1.25M), Gln=Asn (0-0.2M). Arginine. histidine and glycylglycine were ineffective.
The decreases in log
kD, showed that the protective effects against the denaturation of myofibrils were nearly addivtive for all pair combination selected from among Na-Glu, Na-Asp, Gly, sorbitol and surose.
The effect of amino acid and the cooperating effect of the studied mixtures were practically unchanged over the temperature range (25-45°C) at which the myofibrils were treated.
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