For consistency, non-vintage wines can be blended from more than one vintage, which helps wine-makers sustain a reliable market image and maintain sales even in bad years. One recent study suggests that for the average wine drinker, the vintage year may not be as significant for perceived quality as had been thought, although wine connoisseurs continue to place great importance on it.
Some people have allergies or sensitivities to foods which are not problematic to most people. This occurs when a person's immune system mistakes a certain food protein for a harmful foreign agent and attacks it. About 2% of adults and 8% of children have a food allergy. The amount of the food substance required to provoke a reaction in a particularly susceptible individual can be quite small. In some instances, traces of food in the air, too minute to be perceived through smell, have been known to provoke lethal reactions in extremely sensitive individuals. Common food allergens are gluten, corn, shellfish (mollusks), peanuts, and soy. Allergens frequently produce symptoms such as diarrhea, rashes, bloating, vomiting, and regurgitation. The digestive complaints usually develop within half an hour of ingesting the allergen.
Wine cellars, or wine rooms, if they are above-ground, are places designed specifically for the storage and aging of wine. Fine restaurants and some private homes have wine cellars. In an active wine cellar, temperature and humidity are maintained by a climate-control system. Passive wine cellars are not climate-controlled, and so must be carefully located. Because wine is a natural, perishable food product, all types—including red, white, sparkling, and fortified—can spoil when exposed to heat, light, vibration or fluctuations in temperature and humidity. When properly stored, wines can maintain their quality and in some cases improve in aroma, flavor, and complexity as they age. Some wine experts contend that the optimal temperature for aging wine is 13 °C (55 °F), others 15 °C (59 °F).
Most food has its origin in plants. Some food is obtained directly from plants; but even animals that are used as food sources are raised by feeding them food derived from plants. Cereal grain is a staple food that provides more food energy worldwide than any other type of crop. Corn (maize), wheat, and rice – in all of their varieties – account for 87% of all grain production worldwide. Most of the grain that is produced worldwide is fed to livestock.