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. TSPME, 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 μm to 1 mm and maintained a monomodal distribution. After 27 d of storage at 4 °C, samples of clarified juice still showed a large population of small cloud particles when measured by diffraction light scattering.