Fried foods are not only great for your taste buds; they are enjoyable to prepare. Very little else beats the delightful crunch of fried chicken and a side of fries. The only downside to this is that you have to use a lot of oil for perfect cooking, thus the frequent worry over how long frying oil remains safe to be reused.
Experts say for the perfectly fried chicken; you may need as much as 2 quarts of oil. So, reusing the oil, again and again, seems very understandable. What is most important is that you never forget to strain the oil immediately after use to prevent contamination or bacteria growth.
Caution: only strain the oil after it has cooled down!
However, oil reused too many times starts to have unpleasant effects on the finished products. Thus, the need for you to know just when to throw out your frying oil.
According to experts, the number of times you can reuse oil without any adverse effects depends on what you are frying.
The critical rule is that: "you should replace oil used to fry animal products more often than replacing the oil to fry plant-based products."
Therefore, experts predict that if you properly strain oil used to fry chicken or fish, you should be able to use it four times. A trial performed to examine this showed that the product was "greasy" and had an "off" flavor on the fifth time of reusing oil to fry chicken.
Conclusion: it is best advised that you only reuse oil to fry meat products four times.
As for the trial conducted on vegetable products, the same oil was used for frying potato chips. It was discovered that there was no observable difference between the flavor of the first batch and any of the successive batches. The experiment went through eight batches without finding any negative difference.
Conclusion: Although it is not advisable to reuse oil forever when frying vegetable products, you'll be able to use it for quite a long while without noticing any differences.