Interlaken white grapes

In addition to the Concord grapes I have been sharing recently, our property also has three Interlaken white grape vines. I have been nurturing them along all summer but they are just not what I would call a pleasant tasting table grape. I have a feeling that the previous gardener must have been a winemaker. Too bad because that is not at all what we would do. They look pretty, but are not sweet. Maybe they are not totally ripe yet? It seems late in the season now, but I will just let them be.