Vegetable oils are probably the most commonly used of all the oils. They are easily found in most condiment aisles in the grocery store. These oils include: general vegetable oil, canola oil, corn oil and sunflower oil. The oils are used in recipes for cooking, preparation and for dressing. Most vegetable oils, if unopened, have a shelf life of about a year. Once the vegetable oil is opened, it can be safely used for four to six months.
Olive and Peanut Oils
Both olive and peanut oils require the same storage guidelines as vegetable oil, but these oils are capable of an extended shelf life with a little extra care. Like vegetable oil, these two oils both have a shelf life of about a year, unopened or 4 to 6 months if opened. The difference is that olive and peanut oils are both high in monounsaturates and benefit most from being stored in the refrigerator, where the cold lengthens the oils shelf life from six months to about a year. The refrigerated oil becomes cloudy and thickens up in the cold but you can let it rest outside the refrigerator before using it.
Walnut and Sesame Oils
Walnut and sesame oils are both delicate and become rancid quickly, even if kept in a cool, dark cupboard. Kept in a pantry or cupboard, walnut and sesame oils have a shelf life of about four to six weeks, however if the oils are kept in the refrigerator, they will stay fresh for two to four months. Freshness also depends on the preparation of the oil. Oils with preservatives added have a longer shelf life than all-natural brands, but the trade-off is healthy cooking. Store these oils in the refrigerator, however do not worry if they become thick. Reconstitute the oil to normal consistency by holding the bottle under warm running water.
Storing Oils Properly
Storing oils properly is the best way to enhance the shelf life of any bottle of cooking oil. The oils should always be covered tightly and stored far away from heat. This includes storing oils in a pantry or cupboard over or near a stove. The less air they come in contact with, the fresher the oils will stay, which is why refrigerating is OK. Always smell or taste an oil before using it if you haven't used it in awhile.