Why the epitaph on my urn will read “Twittered Away”: I posted that we bought a loaf of rye from a new vendor at Union Square and it turned out to be hardtack — $$ hardtack at that. Within minutes followers were Tweeting thoughts on “vintage hardtack” and, even better, “artisanal hardtack.” Through the reaction, I learned why more and more breads are turning up in the Greenmarkets: The future of local food looks “value-added.” Apparently baked goods sell out much faster than fruits and vegetables that need to be converted into dinner. No wonder our every trip to a market yields more sightings of canned squash, peppers as paprika, tomatoes in sauce and any of the above as part of gift boxes. I’m so old I remember attending a meeting of Greenmarket overseers back in the early Nineties when the arguments over rules were long and furious. Keeping it pure was the big goal, when farmers were really struggling to make a go of it all. And I’m open to new vendors — our neighborhood market now has almost everything we need for a full week: fish, meat, poultry, eggs, cheese, vegetables, fruit. But the things we don’t buy are the “value-added”: the ice cream, the margarine-tasting cookies, the jams. Aren’t those what the neighboring Whole Foods is for?