In an ideal world, you would use fresh oil every time you wanted to fry foods such as chicken or chips. This, however, may not always be possible due to budgetary constraints. Hence, when you are planning to reuse leftover oil, make sure that you cool, manually filter (or use a cooking oil filter machine) and store it properly. Improperly stored oil may produce dangerous free radicals which can cause health problems such as heart disease and cancer.
Cooling the Oil
After frying your foods, switch off the heat and let the oil cool completely until it is at room temperature with no residual heat. Burns caused by oil burns are extremely painful so you must make sure that you cool the oil properly before proceeding to the next step.
Filtering the Oil
Once the oil is cool, it is easiest to use an oil filter machine. You simply pour the used oil into the machine and let it do its job. To filter the oil manually, use a coffee filter or a fine-meshed sieve covered with at least two layers of cheesecloth. The cloth will filter any fine matter left behind in the cooking process. While it may be tempting to keep the residue for ‘extra flavour’, these tiny bits will burn and make the oil taste bitter when reheated. Thus, it is best to filter all of it out of the oil.
Storing the Oil
Transfer the filtered oil into a clean container, preferably a glass jar. Alternatively, you may use the original bottle that the oil came in. Use a funnel to transfer the oil, gently pouring it into the container, then store it in a cool, dry place.
Reusing the Oil
Keep two things in mind when you plan to reuse your oil. First, oil absorbs the flavour of whatever you fry in it. Given this, it is best to reuse the oil to cook similar foods. Second, when frying, start with foods that leave the least amount of debris and flavour. This way, there is less likelihood of infusing the oil with a bitter flavour.
Be aware, however, that there is a limit to the number of times you can reuse your oil. When you find that the oil is no longer usable, do not pour it down the drain as this will clog your pipes and is bad for the environment. Instead, place it in an old, sealable container and dispose of it carefully.