Food Science Universe (FSU)

Blanching of Fruits and Vegetables (English)

The blanching test will examine the effectiveness of boiling water blanch. Focus your attention to assess the influence of size and retention time on enzyme inactivation.

Blanching of Fruits and Vegetables

  • Steel Kettle


  • Select two sizes of potato/apple pieces from the size reduction experiment.
  • Divide into four lots.
  • Subject each lot to heat treatment in boiling water or steam for 1, 2, 3 and 5 minutes.
  • Cool the product rapidly in running water.
Subject each lot to the following Peroxidase Test:
  • a. Place 25 g potato samples in the blender.
  • b. Add 150 mL distilled water and blend for 2 min.
  • c. Filter or centrifuge.
  • d. Transfer 2 mL filtrate (supernatant) into a clean test tube containing 20 mL distilled water.
  • e. Add freshly prepared 1 mL 0.5% guaicol solution and 1 mL 0.08% H2O2.
  • f. Mix thoroughly by inverting and observe for colour development.
  • g. If no colour develops in 3 or 4 min, the test is negative and blanching is adequate.


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