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Starch Index Scale


December 21, 2023 - <> and the MSU Apple Maturity Program

Suggested controlled atmosphere storage starch index and firmness levels for commercial apple varieties in Michigan, including: Ambrosia, Braeburn, Empire, Evercrisp, Fuji, Gala, Golden Delicious, Granny Smith, Honeycrisp, Idared, Jonagold, Jonathan, Pink Lady, Red Delicious and Rome.

Testing Instructions

  • Collect a sample of apples from the orchard. Maturity tests should be performed on at least 10 fruit to represent the average in the block. Samples should be at least room temperature for best results.
  • Stain apples as soon as possible after samples have been collected. Use an iodine solution of 10g I2 and 40g KI per gallon.
  • Cut apples in half at the equator. Immediately dip, spray, or roll starch solution on cut surface.
  • Wait for pattern to develop, which may be several minutes, but rate sample within 20-30 minutes before cut surface of fruit turns brown.
  • Compare each fruit with patterns in this chart and record the corresponding starch value.



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