How to keep the (deep frying) oil usable as long as possible

deep-fryingfood-safetyfryingoil

I have a new deep fryer. I am pleased with its results so far. I am not a 'heavy user' though – say once every 2-3 weeks. I want to re-use the oil a couple of times. The deep fryer is covered but not airtight, however.

The new deep fryer has a cold zone, which means the oil won't become dirty due to particles over-frying. I don't overheat the oil either. So, in principle, I'm frying correctly, I think.

So, how long can my oil safely sit in the deep fryer, if I ensure it's thouroughly heated next time I fry? Should I be allowing the oil to cool and store the fat in (sealed) containers instead, if there's going to be this long a gap between uses?

Edit: yes, I've seen this question and answers: Frying Oil Reuse

Best Answer

I would not reuse that oil. The frying-oil reuse that occurs in fast food chains is reuse for the same day or over just a few days. They also store it properly and not just sitting exposed in the fryer.

justkt is correct that more saturated fats are less sensitive to breakdown, this is why bacon grease can be kept for a rather long time.

Three factors play a significant role in oil degradation:

Oxidation

Any contact with air causes oxidation in oil. High temperatures, metal alloys, surface exposure, and even UV light act as catalysts to this reaction.

Hydrolysis

When water interacts with oil it causes it to taste tainted or acidic. This is exacerbated by high temperatures, heating/cooling cycles, and oxidation products.

Polymerizaton

When frying oil deteriorates, the resulting products form both volatile (or reactive) and non-volatile compounds. Non-volatile compounds remain within the frying oil, and can produce polymerization at frying oil temperatures above 200°C (390 F) or in isolated hot spots within the frying system. These molecules bond together to form large, different-sized clusters that accumulate on the oil’s surface. Since they don’t dissolve, they cause foaming; trapping air under the oil, and increase the possibility of hydrolysis.

Given all these, the best environment for any oil is an cold, dark, airtight place. Cold temperatures may cause clouding, but this is not a cause for worry.

Source:

http://www.heatandcontrol.com/technical%20articles/Maximizing%20Cooking%20Oil%20Life.pdf

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