Aloe vera is best harvested and used fresh on an as-needed basis. When it is necessary to preserve aloe vera gel for later use, freeze or dry the gel until you're ready to use it. Mixing the gel into vitamin E oil or citric acid also will preserve the aloe.
Cut the aloe leaf close to the base of the plant and wrap the whole leaf in cling film. Place the wrapped leaf into a plastic bag and seal. Store the leaf in the freezer until ready to use the aloe vera gel. Thaw the leaf before cutting it and extracting the gel.
Drain the sap from a cut aloe vera leaf, then remove the gel inside. Allow the sap and gel to evaporate until it forms a brown crystalline solid. Use the dried gel by adding it to lotions, creams or other preparations.
In a dark glass container, add 1 tsp citric acid to 680 g (3 cups) aloe vera gel; store the container in the refrigerator for several weeks. If the gel becomes dark, discard the gel. Another option is to mix 15 drops lavender essential oil, 1 tsp vitamin E oil, 1 tsp vinegar and 118 ml (4 oz). aloe vera gel into a spray bottle to use as a sunburn spray. Store the spray in the refrigerator. Alternatively, mix only the aloe gel and vitamin E oil and refrigerate.