Capillary electrophoresis analysis of orange juice pectinesterases |
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Authors: | Braddock R J Bryan C R Burns J K |
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Institution: | University of Florida, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, Florida 33850, USA. rjbk@lal.ufl.edu |
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Abstract: | Pectinesterase (PE) was extracted from orange juice and pulp with 1 M NaCl, desalted, and separated using capillary electrophoresis (CE) gel procedures (CE-SDS-CGE) and isoelectric focusing (CE-IEF). PE resolved as a single peak using noncoated fused silica columns with CE-SDS-CGE. CE-IEF separation of PE required acryloylaminoethoxyethanol-coated columns, which had limited stability. Thermal stability of PE extracts before and after heating at 75 degrees C for 30 min and at 95 degrees C for 5 min established heat labile and heat stabile fractions with identical PE migration times by CE-SDS-CGE or CE-IEF. Peak magnitude decreased to a constant value as heating time increased at 75 degrees C. Regression analysis of CE-SDS-CGE peak migration times of molecular weight (MW) standards estimated both heat labile and heat stable PE at MW approximately 36 900. Traditional SDS-PAGE gel separation of MW standards and active PE isolated by IEF allowed estimation of MW approximately 36 000. CE-SDS-CGE allowed presumptive, but not quantitative, detection of active PE in fresh juice. |
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