Published 3 July 2026 at 15:11
In a deep fryer, you make the choice every day: should I keep the oil a little longer? Oil that is too fresh lacks the characteristic flavor, while oil that is too old makes the fries bitter and poses health risks. The standard answer in professional kitchens is “change it when it looks dark” or “change it every X days” — but both methods cost money. A quick test that objectively measures the actual condition of the oil is what makes the replacement decision economically sensible. ETI’s test strips for frying oil perform this measurement in two minutes, for almost nothing.
What the strips measure
ETI test strips measure free fatty acids (FFA) in the oil. During heating, the triglycerides in the oil gradually break down into free fatty acids — and the FFA level is the best objective indicator of the oil’s degradation level. Freshly changed oil has very low FFA (under 0.5%). At FFA levels above 2.5–3%, the oil is considered degraded; the taste is significantly affected, the smoke point drops, and health risks increase (due to polar oxidizing compounds).
The test is based on a simple neutralization reaction: the reagent on the strip contains potassium hydroxide (KOH) and a color indicator. The free fatty acids are neutralized by the KOH and change the pH of the reagent mixture — resulting in a color change. The higher the FFA content in the oil, the greater the color change, which is directly compared with the included color chart.
How the test is performed
- Wait until the oil is cool (below 40 °C) — the test strip does not react correctly in hot oil.
- Hold the strip by the white end and dip the entire colored band into the oil for 2 seconds.
- Remove the strip and wait for 2 minutes.
- Compare the strip’s color with the included color chart.
The entire process takes less than 3 minutes, including waiting time. The test is recommended at the beginning of each shift before the oil is heated up — before making critical decisions about continuing to use the oil or replacing it.
The economics of measuring correctly
An average commercial deep fryer holds 15-25 kg of oil. Quality oil costs 30-40 SEK per kg. Replacing the oil too early wastes 500-1000 SEK per fryer. Replacing it too late compromises the quality of the meals and risks health problems for guests. The balance between the two — measured objectively — is where the test strips pay for themselves.
With 100 strips per pack for 540 SEK, each test costs approximately 5.40 SEK. On a day with two fryers tested at the start of the shift, that amounts to 11 SEK — negligible compared to the 500-1000 SEK per fryer and replacement that poor timing costs.
Where the test strips are used
Fast food chains and chain restaurants: Standardized routines for all staff. Test strips eliminate the subjective assessment of oil condition and provide reproducible decisions regardless of who performs the test.
Frying operations and fish-and-chips restaurants: Where fried food is the core product, oil quality is crucial for taste. Regular measurement maintains consistency over time.
Institutional catering and school kitchens: Many schools and nursing homes serve fries and fried food regularly. Economic management of the oil budget is part of the systematic work.
Hotels and conference centers: Buffet service where the amount of fried food varies throughout the week. The test strip determines whether the oil from last weekend can still be used.
Food trucks and mobile catering: Where storage space is limited and oil must be managed efficiently. The test strip is cheap, compact, and requires no electronics.
Food production: Chip factories, donut manufacturers, and other commercial frying operations use FFA measurement as part of quality control. Test strips complement the more advanced laboratory measurements that are performed less frequently.
Restaurant chain consultants: When advising or auditing restaurants, test strips are a quick and objective way to assess operational routines.
What you get for the money
100 test strips in a storage bottle with an easy-to-read color chart. Works equally well with animal fat, vegetable oil, and A/V blended frying oil (shortening). No sample preparation or special training is required. The instructions are simple enough for anyone to understand in five minutes.
540 SEK for 100 tests is one of the cheapest quality assurance measures you can implement in a commercial kitchen operation. Calculated against a single avoided incorrect oil change, the product pays for itself hundreds of times over.
Read more: ETI test strips for frying oil in the shop →
