What causes a black color in home-canned beets?
This condition indicates spoilage. No unusual odor or gas is present. The black color may extend throughout the beet. A distinct medicinal flavor may be present. Iron must be present for the bacteria to develop this color. Iron can come from water, an iron kettle or a chipped enameled-ware utensil. Do not consume.
References: KSU "The Food Spoilage Chart" Weiser: Practical Food Microbiology and Technology
Last update: Tuesday, May 05, 2009