Once tomatoes shed their reputation for poison, they became the most versatile vegetable in American kitchens. While tomatoes are available year-round any fool knows that they’re best in season and locally grown. Any produce vendor in the American South is going to keep at least one big bin usually right up front and center full of field tomatoes grown by small truck farmers and delivered every morning. When you’re buying from one of these people–and it’s the only place you should buy tomatoes in the summer–it’s hard to go wrong, but there are a few things you should bear in mind.
Use your common sense. Choose uniformly firm fruit, without any squishy spots, bruises or dark spots. The most commonly-grown field tomatoes in central Mississippi and likely throughout the mid-South are Big Boy, Better Boy, Celebrity and (Arkansas) Traveler, all of which are more or less red-ish the Traveler tending to pink. Most of the old-school produce vendors will occasionally have “cherry” tomatoes of some kind or the other in season, but you’ll have to find markets that support specialty growers, such as the Mississippi Farmers’ Market, to get the varieties such as Cherokee, Krim or any of the various yellows. You can of course always get good green tomatoes for pickling or frying.
Remember that the tomato is a climacteric fruit, which means they ripen (i.e. become softer and sweeter) after harvest. The biochemical process involved is that climacteric fruits give off large amounts of ethylene gas whereas non-climacteric fruits give little or no ethylene gas. Non-climacteric fruits, once harvested, never ripen further; you can find an extensive list here. Tomatoes sold in the winter and for the most part any sold in big chain supermarkets are picked green and “gassed”, sprayed with ethylene during shipping, which forces coloration, but not sugar production. When you buy from the produce stand, however, pick a few to use immediately and a few on not-quite-ripe side to ripen naturally on your kitchen shelf. Turn the tomatoes stem-end down to ripen, since the blossom end will mature first and the firm stem end will better support the fruit.
You shouldn’t have to refrigerate unsliced summer tomatoes at all. If you don’t stack them, they’ll keep for several days, and you should eat them at such a pace that they don’t need refrigeration. Remember with every bite you take that autumn will be here all too soon, and winter right behind.