SOURSOP PECTINESTERASES - THERMOSTABILITY AND EFFECT ON CLOUD STABILITY OF SOURSOP JUICE

The thermostability of two forms of purified pectinesterase from sours op fruit were studied. The heat stability data showed, that PE I is mo re heat stable than PE II at pH 7.5. The D and Z values were evaluated in the range 45-75 degrees C. The D values at 65 degrees C were appro ximately 5.8 min and 3.3 min for PE I and PE II respectively. The chan ges in temperature required to increase the inactivation rate tenfold (Z value) were calculated at 8.5 and 8.6 degrees C for PE I and PE II respectively. Both enzymes also tested positive for their ability to d estabilise soursop juice cloud at 5 and 30 degrees C. Cloud destabilis ation by PE I occurred the fastest (large decrease in A 660 nm) in the natural juice at 30 degrees C. Copyright (C) 1997 Published by Elsevi er Science Ltd. All lights reserved.