EFFECT OF COMBINED PRESSURE AND TEMPERATURE ON SOYBEAN LIPOXYGENASE -1 - INFLUENCE OF EXTRINSIC AND INTRINSIC-FACTORS ON ISOBARIC-ISOTHERMAL INACTIVATION KINETICS

Both isothermal and isobaric-isothermal inactivation of soybean lipoxy genase (LOX) could be accurately described by a first-order kinetic mo del. Thermal inactivation of LOX at atmospheric pressure proceeded in the temperature range 60-70 degrees C, whereas pressure-temperature in activation occurred in the pressure range 50-650 MPa at temperatures b etween 10 and 64 degrees C. With increasing pressure at constant tempe rature, a consistent increase in inactivation rate constants was noted , pointing out a negative activation volume. At constant elevated pres sure, on the other hand, a temperature of maximum stability was observ ed, generally situated somewhat above room temperature, indicating the Arrhenius law not to be valid over the entire temperature range. Fina lly, the influence of some food-relevant intrinsic factors on thermal and pressure-temperature stability of LOX was screened. Where enzyme c oncentration only slightly affected thermal and pressure stability of LOX, both pH and flushing with CO2 effected significant stability chan ges.