Juice squeezed directly from a lemon is referred to as "fresh." as opposed to lemon juice that is processed and sold in bottles. Bottled lemon juice keeps much longer than fresh due to added preservatives manufacturers use to increase the shelf life. However, the vitamin content of fresh lemon juice is higher than bottled. Uses for fresh lemon juice include lemonade, salad dressings, marinades and seasonings in cooking. In order to preserve the flavor and vitamin content of fresh lemon juice, it is necessary to store it correctly.
Whole lemons will stay fresh for up to two weeks at room temperature, and up to six weeks in the refrigerator. Once expressed, however, lemon juice will not stay fresh as long as the whole lemon. Fresh lemon juice is highly flavorful, and a good source of vitamin C, but both the taste and nutritional value rapidly deteriorates the longer the juice stands. Freshly expressed lemon juice should be used or stored immediately after it has been squeezed to take advantage of the best taste and nutritional value.
When storing expressed lemon juice in the refrigerator or freezer, it must be stored in an airtight bag or in a container with a tight-fitting lid. This reduces the exposure to air and keeps the juice fresh and flavorful. Freshly squeezed lemon juice will stay good for two to three days in a tightly sealed container in the refrigerator. During refrigerator storage, fresh lemon juice may separate into juice and sediment. Lemon juice that has a layer of settled debris on the bottom is still suitable for use, and can be strained, or poured into another container to retain clarity. Large quantities of lemon juice can be frozen in freezer bags or containers. If tightly sealed, frozen lemon juice will stay fresh in the freezer for up to four months.