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PL1 - Flesh Firmness

  • Start monitoring the flesh firmness of the plums in the orchard at least 10 days prior to the expected harvest date as the correlation between flesh firmness and skin colour may vary from orchard to orchard and from year to year.
  • Sample fruit at the same time in the morning when it is still cool.
  • Sample fruit which is representative of that which will be picked in the first harvest.
  • Each orchard of a particular cultivar must be tested separately.
  • A minimum of 20 plums (preferably 40) randomly selected is required per orchard.
  • Remove a thin slice of peel from opposite sides on the centre (cheek) of each plum.
  • Hold the plum firmly in one hand and rest your hand on a rigid surface.
  • Zero a calibrated penetrometer and place the plunger head of 11.0 millimetres in diameter on the spot where the skin was removed.
  • Apply steady downward pressure on the penetrometer until the plunger has penetrated the flesh of the plum up to the depth mark indicated on the plunger.
  • Remove the plunger and note the reading on the pene­trometer, to one decimal.
  • Repeat the process on the opposite side of the same plum after zeroing the penetrometer.
  • Determine the average of the two pressure readings for each plum and the average for all the plums tested.
  • Take flesh firmness readings at least every 3-4 days and at closer intervals near harvest time and plot the rate of change in order to schedule the harvest in the optimum maturity window.
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