Yes. For solid fruits the following procedure is recommended:
Accurately weigh approximately 4 g of sample and homogenise in 10 mL of 1 M potassium phosphate buffer (pH 3.5) with an Ultraturrax® or Polytron® homogeniser (or equivalent) to effect complete disintegration. Adjust the pH to 3.5-4.0, if necessary, with 2 M KOH and quantitatively transfer the slurry to a 100 mL volumetric flask. Rinse the homogeniser shaft with water and add these washings to the flask. Fill to the mark with 100 mM potassium phosphate buffer (pH 3.5) then filter through Whatman No. 1 filter paper or centrifuge at 13,000 g. Use the filtrate/supernatant in the assay with an appropriate dilution in distilled water if required.
If coloured solutions require analysis undiluted, they may need decolourising as follows: stir 10 mL of liquid sample for 5 min with 0.2 g of PVPP and then filter through Whatman No. 1 filter paper or centrifuge at 13,000 g. Use the clear/slightly coloured filtrate/supernatant directly in the assay.
Ascorbic acid extracts may be stablised by the addition of tert-Butylhydroquinone (TBHQ, tertiary butylhydroquinone) at a final concentration of 1 mM.


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