Partial characterization of the in situ activity of pectinesterase in Bramley apple

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Abstract
Summary: The characteristics of pectinesterase (PE) have been examined in waste material (peel, cores and offcuts) obtained from Bramley seedling apples barn stored for 2, 4 and 12 weeks. A crude enzyme extract was prepared by suspending the dried and milled apple waste in 0.1 m NaCl at pH 8.5. The activity of PE under standard assay conditions of 0.5% apple pectin, 0.1 m NaCl, pH 8.5 and 30°C was low, between 4 and 8 units g−1 dry matter, but activities up to 60 units g−1 dry matter were obtained at higher temperatures. The optimum temperature was 60°C with the enzyme stable up to 40°C with 5 min heating. The mean activation energy for PE in the three samples was calculated at 39.2 kJ mol−1 K−1. The optimum pH was high at 10.0 probably due to the PE assay measuring the extraction/solubilization and stability of the enzyme in addition to its activity. Optimum activity was obtained in 0.15 m NaCl with optimum stability at 0.5 m.

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