34°F - 40°F.
Refrigerator temperatures do not destroy pathogenic or spoilage microorganisms. The lower temperature does, however, slow the growth of microorganisms already in the food. Perishable food will deteriorate, even at refrigerator temperatures, due to spoilage microorganisms, enzymes and oxidation. Time and temperature are important factors in food quality. Normally a domestic freezer is best set to −18 °C (0 °F) or colder, as that's what the expiration dates for many food items are based on. It's also a requirement for freezers in restaurants, supermarkets & other places that sell food (at least here in Europe) to maintain a temperature of at most -18 °C. A general purpose domestic fridge should be at around 1-4 °C (so, just above the freezing point, and below 5 °C). 34°F - 40°F is the ideal refrigerator temperature range. Some Web sites just say under 40°F, but not so cold to freeze fresh foods. Dairy products and meats keep best at the low end of the temperature range. A freezer should be set at 0°F, or lower, if possible. If the temperature gets warmer than +5°F, ice cream will be too soft and won't keep well. A properly working food freezer will operate in the range of -10°F to +2°F, and may go up to around +8°F briefly during the defrost cycle if it is of the frost free type.  If you keep potatoes in the fridge they should not be stored at temperatures below 7 °C (45 °F). If, that is, you intend to use them for roasting for frying. At lower temperatures the starch in the potato breaks down giving a burnt look and a bitter taste after roasting. It's also a requirement for freezers in restaurants, supermarkets & other places that sell food (at least here in Europe) to maintain a temperature of at most -18 °C. A general purpose domestic fridge should be at around 1-4 °C (so, just above the freezing point, and below 5 °C). 1 Fridge: put the thermometer in a glass of water. 2  Check the temperature during the first door opening after not using the fridge for 8 hours or more (such as overnight). 3  Freezer: put thermometer between two bags of vegetables and as above check after 8 hours or more. To measure the temperature: 1  Therefore, you want your refrigerator to be cold, but not so cold that it freezes things. The preferred temperature is somewhere between 35 and 38 degrees F (1.7 to 3.3 degrees C). Anything higher and foods will spoil too quickly (it also presents food poisoning problems, as described in several of the links below). According to Keeping Food Fresh by Janet Bailey: Some foods need temperatures warmer than your refrigerator but cooler than your pantry. Fresh potatoes and winter squash for example keep best at a temperature of around 50°F. to 55°F. It's also a requirement for freezers in restaurants, supermarkets & other places that sell food (at least here in Europe) to maintain a temperature of at most -18 °C. A general purpose domestic fridge should be at around 1-4 °C (so, just above the freezing point, and below 5 °C). 1 Keep the refrigerator temperature at or below 40° F (4° C). 2  The freezer temperature should be 0° F (-18° C). 3  Check temperatures periodically. 4  Appliance thermometers are the best way of knowing these temperatures and are generally inexpensive. 1 Also, when putting food away, don't crowd the refrigerator or freezer so tightly that air can't circulate. 2  Keep your appliances at the proper temperatures. 3  Keep the refrigerator temperature at or below 40° F (4° C). 4  The freezer temperature should be 0° F (-18° C). 5 1 If you do lose power, keep the doors to your fridge and freezer closed as much as possible to keep foods cold. 2  Before using any foods, check your refrigerator and freezer thermometers. 3  If the fridge is still at or below 40 °F, or the food has been above 40 °F for only two hours or less, it should be safe to eat. Even when your refrigerator and freezer are chilling foods at the right temperatures, and you've followed all the other rules for safe storage, there are limits to how long you can safely store foods in the refrigerator. (Foods will stay safe indefinitely in the freezer, but quality/taste of the food may be affected.). In order to keep food out of the Danger Zone, your fridge must be set between 32-40° F (0-4 degrees Celsius). Your freezer must be below 32° F (0° Celsius). I keep mine as cold as it will go. Keep your freezer efficient by half-filling it with bottles of water. Your refrigerator probably isn't set right, and your food items may not be where they should be in your fridge. The kitchen fanatics at Stack Exchange offer a couple tips on ensuring your perishables don't perish.
http://food.unl.edu/refrigerator-and-freezer-storage http://cooking.stackexchange.com/questions/4529/what-temperatures-should-i-keep-my-refrigerator-and-freezer-set-at http://www.answers.com/Q/What_is_the_best_temperature_for_a_refrigerator_and_freezer http://cooking.stackexchange.com/questions/4529/what-temperatures-should-i-keep-my-refrigerator-and-freezer-set-at http://www.knowhow.com/article.dhtml?articleReference=786 http://home.howstuffworks.com/appliances/energy-efficient/question121.htm http://cooking.stackexchange.com/questions/4529/what-temperatures-should-i-keep-my-refrigerator-and-freezer-set-at http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm093704.htm http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954.htm http://lifehacker.com/what-temperature-should-you-keep-your-refrigerator-set-533534221
best temperature for fridge