http://www.durgan.org/URL/?KFLCT 11 September 2010 Concord Grape
One plant in the fifth year produced 30 pounds of excellent quality grapes. The fruit was processed into 15 liters of juice with about a quarter of the juice being processing water. The grapes were washed, boiled for 20 minutes, and made into a mash, then strained to remove fiber, then placed in liter jars and pressure sterilized for long term storage at room temperature. About two pounds of grapes were used to make one liter jar of strong juice, which is about one part water to four parts grape juice of finished product.
The previous best yield from this cultivar was 12 lbs in 2008. The crop fell off the vines in 2009 due to cold wet weather.