In European pears the main
Cell wall fractions were extracted according to methods previously described by Brummell et al. (2004) with slight modification. The powdered frozen flesh sample (3.0 g) was homogenized in 8 mL of 80% ethanol, stirred for 20 min at 80 °C and then centrifuged. The precipitate was washed with 80% ethanol and pure acetone three times and then sequentially immersed in 95% dimethyl sulfoxide (DMSO) for 12 h before centrifuging to remove the starch in the supernatants. Finally, the residue was dried until it SB 225002 was a constant weight at 45 °C in a ventilated oven, and the dried residue was considered to be the cell wall material (CWM). 50 mg CWM was extracted with distilled water and then centrifuged (15 min at 4000 × g). The supernatant was designated as the water-soluble pectin (WSP) fraction. The precipitate was sequentially dispersed with trans-1,2-diaminocyclohexane-N,N,N9,N9-tetraacetic acid (CDTA) and Na2CO3 containing 0.1% NaBH4 for 24 h to obtain CDTA-soluble pectin (CSP) fraction and Na2CO3-soluble pectin (NSP) fraction, respectively.. These three pectin fractions were quantified as uronic acid content using the carbazole method (Bitter and Muir, 1962) with three replications per sample.