Clarification of Valencia orange juice is influenced by specific activity of thermolabile pectinmethylesterase, inactive PME-pectin complexes and the changes in serum soluble components
Ackerley, Jennifer Lynn
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Clarification of orange juice is a quality defect attributed to pectinmethylesterase (PME). Thermolabile PMEs with different specific activities were added to stabilized juice. Particle size distribution, % transmittance, uronic acid analysis and SDS-PAGE were used to monitor clarification overtime. Juices with the highest specific activity clarified at the slowest rate and contained 36 and 13 kDa peptides. Juices with a 36 kDa and 27 kDa peptide clarified juices fastest. In fresh juice with cloud insoluble solids (PFJ) and juice with only cloud soluble solids (UCS), UCS formed a floc concurrently with clarification of PFJ. The clarification of juices adjusted to pH 7 was retarded due to electrostatic repulsion while juices at natural pH clarified more rapidly. These results show that serum-soluble factors, total charge and electrostatic interactions influence cloud destabilization.