Juice clarification by thermostable fractions of marsh grapefruit pectinmethylesterase

Orange juice clarification by thermostable pectinmethylesterase (TS-PME), isolated from grapefruit pulp by ammonium sulfate precipitation, and ion-exchange and affinity chromatography was investigated. TS-PME, having different specific activities, induced different clarification behavior of reconstituted orange juice at 2 units/ml. Based on percent transmittance, TS-PME fraction with the lower specific activity clarified juices earlier than TS-PME at higher specific activity. Particle size distribution of the cloud-soluble fraction showed that TS-PME increased the average particle size from 0.7 mum to 1 mum and maintained a monomodal distribution. After 27 d of storage at 4 degreesC, samples of clarified juice still showed a large population of small cloud particles when measured by diffraction light scattering.