Although sugar is a vegetable product, made from sugar cane or sugar beets, it's processed in such a way that it's almost impervious to bacterial growth. Unlike most of the foods in your kitchen, it doesn't need to be refrigerated or frozen. Keep one small container of sugar accessible in your refrigerator and store larger quantities in a food-safe plastic container in a basement or pantry.

Although freezing is ideal for preserving many foods, it's not the best choice for granulated sugar. Sugar easily picks up off-odors that might be present in other frozen foods and can develop a musty taste. It also becomes lumpy if exposed to even a little moisture, another reason you shouldn't store it in the refrigerator either. Chances are, if you're like most cooks, you have limited freezer space. Don't waste this precious space on sugar -- save it for perishable foods, such as meats, grated cheese and breads.

The best way to store sugar is in air-tight, lidded containers, such as food-grade plastic bins, glass jars or polyester film bags. Air, heat, moisture and light are the enemies when it comes to dry food storage, so store sugar in a cool, dry, dark pantry. Properly stored, sugar lasts indefinitely because bacteria doesn't grow in it. However, try to use it within two years for best quality. If you live in a hot, humid climate, use it within one year.

Even with careful storage, sugar may harden or develop lumps, especially if the weather is humid. To deal with moisture in the sugar, heat the oven at its lowest temperature. Place the sugar in an oven-safe bowl and bake it for 10 to 15 minutes, or until it breaks apart when touched. Turn off the oven and leave the sugar in the oven for one hour. Pulverize lumpy sugar in a food processor before repacking it.

Sugar, by itself, is unlikely to mold or spoil when properly stored, but it may spoil if it's been contaminated with other foods. Always use a clean measuring cup when scooping sugar out of a container to avoid mixing it with perishable ingredients. If the sugar shows signs of mold or has an off odor or flavor, discard it, rather than risking illness.