Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

Summary The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase ( PME ), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide ( SC ‐ CO 2 ). Addition of ethanol to the SC ‐ CO 2 at 2% (v/v) caused greater inactivation than SC ‐ CO 2 alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC ‐ CO 2 remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.