Why does my fruit turn dark after processing?
Reasons why fruit turns dark after processing: Fruit did not receive an anti-darkening treatment during preparation. Fruit not processed long enough to destroy enzymes. Temperature not high enough--water not at rolling boil at beginning of processing or water not kept at rolling boil throughout processing time. Time was inaccurately counted--started counting time before rolling boil or failed to check time table or failed to make adjustment for altitude. Boiling water level not 1 inch above tops of jars throughout entire processing time (fruit may turn dark at top of jar). Packing some fruits, like apples or pears, raw that should be precooked. Air was sealed in jars because head space was too large or air bubbles were not removed. The National Canner's Association States: "Darkening of canned fruit in glass containers is caused by exposure to light for an extended storage period, usually at elevated temperatures."
Barbara Willenberg, Nutritional Sciences, University of Missouri-Columbia
Last update: Tuesday, May 05, 2009