THERMAL GELATION PROFILE CHANGES IN RECONSTITUTED ACTOMYOSIN DUE TO STORAGE UNDER A HIGH-SALT CONCENTRATION AND LOW-TEMPERATURE

Changes in the heat-induced gelation properties of reconstituted rabbi t skeletal actomyosin stored under a high salt concentration at pH 6.0 and 0 degrees C were investigated at different weight ratios of actin to myosin by using dynamic rheological and biochemical measurements, The addition of actin resulted in a pronounced peak maximum at about 5 0 degrees C and an accompanying temporary reduction in the range at ab out 50 degrees C to 60 degrees C. The more the initial actin concentra tion was increased, the greater was-the area of the peak/shoulder. How ever, this area was markedly diminished with increasing storage time. As a result, the dynamic rheological pattern was transformed from an a ctomyosin type into a myosin type, The relationship between the G' val ue at 80 degrees C and the actin/myosin weight ratio was curvilinear, with a peak at the ratio of 0.05, immediately after storage was starte d, This profile changed during storage, depending on the extent to den aturation of actin and myosin in the reconstituted actomyosin (RAM), T he G' value of actomyosin in 0.5 M KCl with a small actin/myosin ratio of 0.05 decreased to one-half of its initial value after 7 days of st orage, whereas the G' value,vith a large actin/myosin ratio of 0.225 i ncreased by about 1.6 times, In 1.5 M KCI, all the G' values declined to the level with myosin alone after 7 days of storage, The time-cours e plots of the remaining actin concentration in RAM at different weigh t ratios of actin to myosin after being treated with 0.5 M or 1.5 M KC I showed a decrease in the actin content with increasing storage time, and an increase in the KCI concentration to 1.5 M KCI promoted the de naturation of actin in RAM faster than ,vith 0.5 M KCI, The surface hy drophobicity of each RAM sample progressively increased with increasin g storage time, while little significant increase in the sulfhydryl (S K) content during storage was observed, It is concluded that changes i n the heat-induced gelation properties of actomyosin during storage ar e largely attributable to the denaturation of actin rather than to the denaturation of myosin or to quantitative changes in the SH content a nd hydrophobicity.