How should you be testing cooking oil quality? – Henny Penny


Frying is one of the most popular ways of cooking as it produces exceptional flavor, moisture and crunch. It delivers the ultimate food sensory trifecta: “GBD” or “golden, brown and delicious.” However, repeated usage of frying oil causes it to degrade. Chemical reactions that lead to changes in the oil, which can affect food quality the longer it’s used.


Fried food quality is a function of oil quality. As cooking oil degrades, it affects the texture, taste and overall flavor experience of the food. Because of this, restaurant operators concerned with guest experience are implementing oil quality monitoring programs to ensure their guests get the best quality fried foods. Our own Kimberly Eros answered some questions on the different methods of oil quality testing and how your restaurant can use them to your benefit.


Why do frying oils need to be tested at all?Scientifically speaking, fresh cooking oils are naturally non-polar and almost pure triglyceride, meaning their compounds are symmetrically shaped and not “broken-down.” During the frying process, air, moisture and heat are introduced to the oil. This process begins to break down oil and produce non-triglyceride byproducts that include free fatty acids, alcohols, cyclic compounds and polymers.


What are today’s most common testing methods and what exactly do they test for?
There are several different methods used to measure oil quality ranging from subjective visual inspection to more objective, scientific measurements. Measuring total polar materials (TPM) and free fatty acid values (FFA) are the most predominate indicators for oil quality and are widely used in many international markets where oil quality is strictly regulated.


In the US, where oil is not currently regulated, most operators rely on visual inspection and discard oil based on foaming, odor, smoking, color changes and/or by taste of food products. However, interest among US operators to monitor oil quality is on the rise as operators want to ensure they’re providing a quality experience to their guests. These are some of the methods they’re using today:

An oil colour guide test kit that is used to test the quality of cooking oil when using the Henny Penny Machine | FoodServ

The darker color in the Oil Color Guide Test Kit represents an oil color that’s reached the end of its useful life when frying proteins. The lighter color represents the same but for non-protein foods such as French fries.

1. Oil Color Guide Test Kit: Oil color examples are provided in pre-filled tubes that display oil colors nearing their discard point (these differ dependent upon products being fried). With an eyedropper, an oil sample is taken from the vat and matched against the provided guide colors.

2. FFA Measurement/StripsThese color strips chemically react to the presence of free fatty acids in the oil being tested. After being dipped in the oil, the colors will appear on the strip, which are then compared to the provided color reference chart to determine FFA levels. Standard test strips are designed to measure free fatty acid levels from 2% – 7%, with 5.5%-7% being the discard range.

3. TPM Measurement: These devices determine cooking oil quality by measuring the total polar materials (TPM), or non-triglycerides, based on changes in the dielectric constant, which is measured between two capacitive plates. A TPM reading >25% is considered the discard point in many European countries, although the threshold is dependent upon local regulation. Handheld and integrated TPM measurement devices are currently available.


Is any one of these methods preferred or recommended over the others?
Monitoring an operation’s oil quality is always a good thing as it helps ensure tasty, quality fried foods for your guests. Any method used to monitor oil is better than not monitoring it at all. It’s about finding the right method that works for you and your staff.


What are the advantages and disadvantages of each testing method?
With the oil color guide tubes, the major advantage is cost. They can be purchased for around $30. The process is easy and uncomplicated.

However, the subjectivity of measurement is a drawback. An employee erring too often on the side of disposal when the oil could be used longer, results in higher oil usage and operational costs.

An FFA Strips kit that is used to test the quality of cooking oil when using the Henny Penny Machine | FoodServ

The FFA strips are easy to use and don’t add any interruptions to frying time. They also work for any oil type (vegetable, animal, or vegetable/animal blend). They do, however, come with just an 80% accuracy rate, which is less accurate than TPM methods.


Additionally, each strip is single-use only, so they’ll need to be replenished at an average cost of $300 per year, meaning this method is more expensive than some of the more scientific options. Finally, improper storage can expose and ruin the strips and like the oil reference tubes, the use of a color chart is subjective, possibility resulting in unnecessary oil disposal.


An TPM Measuring device is a handheld measuring device that is used to test the quality of cooking oil when using the Henny Penny Machine | FoodServHandheld TPM measuring devices are generally more accurate (usually to within 90%) and remove the subjectivity of the other previously mentioned methods. Acquisition cost on a handheld device can range from roughly $300 to $500 should you lose or break it. Where these devices fall short is in their overall simplicity of use.

Manufacturers recommend monthly calibrations, a 10+ minute, multi-step procedure, as well as annual testing, which requires shipment to the manufacturer. More frequent calibrations and repairs may be needed if the device is dropped, misused or abused, which could cost $100 to $150 or more, annually. Finally, the measurement procedure is time-consuming, which can interfere with labor, and is dependent on proper operation.


Integrated TPM measuring devices are accurate (within 90%) and less likely to be dropped or abused because they are built into the fryer’s plumbing. Readings are taken automatically during filtration processes and are typically more consistent and accurate as there is even less room for human error. On the other hand, these devices require calibration checks every one to three years, which can cost $250-$700 or more depending upon manufacturer and their calibration frequency requirements.


Are there any other best practices for these testing methods operators should be aware of?
Monitoring oil quality is a fail-safe and objective way to ensure an operation’s food quality. However, there’s a lot in addition to oil quality testing that an operator can do to ensure their fryer oil stays fresh as long as possible.


Regular filtration, proper cleaning and timely maintenance are key to avoiding build-up, which accelerates oil degradation. Avoid exposing oil to metals, salts or UV lights and consider reducing frying temperatures. Finally, make sure all staff is trained on proper frying techniques, fryer usage and care. This training will ensure the consistent delivery of high-quality fried foods for your guests and allow for maximum oil usage, which lowers operating costs.


Oil quality testing is just one aspect of effective oil management. Looking for more answers to your questions regarding oil quality testing or anything else? Our team is happy to help!

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