Air bubbles that are pumped into oil during filtering causes oxidation and impacts flavor.
Example: Leaving the filter pump on after all oil has been pumped out of filter tank.
Prevention: Keep frying vats covered and recirculate oil for 5 minutes during filtering.

Breading and small pieces of food carbonize and cause a chemical reaction that leads to oil breakdown.
Example: Fried food crumbs left in the oil.
Prevention: Skim vats frequently and clean carbon build-up frequently.

Fryers left at high temperatures causes oil to oxidize faster.
Example: Leaving fryers on while unused.
Prevention: Turn off fryers when not in use. Calibrate fryers and set to recommended temperatures.

Water from products, steam, and cleaning break down oil through hydrolysis and causes oil to darken and smoke.
Example: Filter tank is not dry before oil is drained from fryer or excess ice from frozen products.
Prevention: Avoid filling baskets directly over open fryer.  Make sure all equipment is completely dry before use.

Soap produces alkaline flavor and causes oil to darken.
Example: Soap residue from improperly rinsed tools or from cleaning fry vat with soap.
Prevention: Use only hot water to clean inside of fry vats. Properly rinse and dry all tools.

Salt from marinades and breading breaks down oil life.
Example: Salting food before frying.
Prevention: Avoid seasoning food over open vats.