MULTIPLE FORMS OF PECTINMETHYLESTERASE FROM CITRUS PEEL AND THEIR EFFECTS ON JUICE CLOUD STABILITY

Heparin chromatography of a dialysis supernatant fraction from total s alt extractable proteins of Citrus sinensis (L.) Osb. var. Valencia fr uit peel (flavedo plus albedo) resolved four peaks of pectinmethyleste rase activity (PME 1-4), One of these was thermally tolerant (PME 3). Binding to concanavalin A suggested PME 3 was a glycoprotein, At 30 de grees C and 5 U . mL(-1) PME 1, 2 and 3 destabilized the cloud of past eurized FCOJ within 10 days. PME 1 caused the most rapid cloud loss (3 d), followed by PME 3 and PME 2, PME 4 had no effect on juice cloud du ring this time period. At 4 degrees C PME 3 caused the most rapid clou d loss (3d), followed by PME 1 (14d) and PME 2 (>14d), PME 4 had no ef fect on juice cloud stability after 10 days at 30 degrees C or 14 days at 4 degrees C.