Extending the frying oil shelf life whilst maintaining product food safety and quality is one of the goals of food service operators. Filtering the frying oil regularly is by far the most important recommendation to achieve it.

Besides filtering, there are 2 other procedures restaurants follow to try to extend oil life, named frying oil cascading (rotation) or “cradle to grave”.

Frying Oil Cascading

is the procedure where the frying oil is transferred from one vat to another, until it is deemed unfit for use as per food service operator quality standard procedure or legislation.

“Cradle to Grave”

is the method of keeping the frying oil in the same vat that point is reached. 

The oil degrades at different rates in the fryers vats when frying different types of food. When operators use cascading, oil is moved from a Vat with lower debris, lighter oil color (less “hostile” frying oil environment) to Vats with higher debris and darker oil color (more aggressive circumstances).

From experience, the frying oil life is maintained better when the “cradle to grave” operation is followed. There are some technical explanations that could support the preference for the “cradle to grave” approach. Below are the advantages of it:

• No risk of frying oil contaminants being transferred from one frying vat to another.
• Less risk of allergens and off flavors cross contamination among products.
• No work involved in transferring the fryer oil from one vat to another.
• Easier to control frying oil service shelf life via frying oil quality parameters.

By working with the cradle to grave practice, the frying oil is allowed to run its normal degradation course and be discarded when the end point frying oil quality parameter is reached, thus maintaining a longer fry-life.

Therefore, it is always a good practice to maintain cradle to grave approach in restaurant fryer operations to obtain longer oil fry-life and avoid product food safety and quality issues.

The quality of fried food is highly linked to the conditions of frying oil. Although there is not one specific worldwide regulation for frying oil quality, several countries have adopted guidelines or created regulations for the matter. Most of them are based on studies done regarding frying oil stability during cooking and possible deleterious effects in human health.

Nowadays, Total Polar Compounds (TPC) or Total Polar Materials (TPM) is the most common frying oil parameter and the most reliable to determine the oil quality, according to the German Society for Fats Science (DGF). The TPM value provides information on the quantitative proportion of polar and non-polar compounds in cooking oil. In Europe, determining the TPM value has become the standard reference protocol for assessing the quality of fats and oils in deep-frying conditions in foodservice, since it is one of the best quality indicators. As a result, several countries have set the limits of 24 to 27% TPM for degraded frying oil. In countries such as the USA and Australia, where TPM is not a legal limit value, the parameter is becoming increasingly used by foodservice operators as an internal benchmark.

Some countries use acid value (AV) or free fatty acids (FFA) as quality standard. According to American Oil Chemists’ Society Official Methods and Recommended Practices, FFA can be obtained dividing AV by a factor of 1.99.

Below are some countries with guidelines or regulations in place to determine frying oil quality for Foodservice.

Frying oil degradation is a very complex process. It involves several chemical and physical reactions between the frying medium and the product. During frying, physical changes occur, such as heat being transferred from the heating elements to the frying oil and consequently from the oil to the food. Heat causes water in the food to evaporate and reacts with the frying medium.

In addition, there are several chemical reactions occurring among food, frying medium and air. These interactions, influenced by the frying oil, food types as well as frying conditions and oxygen availability are interrelated and produce a complex mixture of substances. The chemical reactions frying oil undergoes are oxidation, hydrolysis and polymerization.

Frying is a popular method of cooking because it is quick, easy and usually results in delicious food.

During the frying process cooking oil is being exposed to heat and all kinds of contaminants (breading, batter, crumbs, marinades, ice particles from frozen food etc.) reducing its lifetime. To extend frying oil service life filtration is the most important step. It helps to control consistency of food and keeps operational costs down.

These are the common methods applied to frying oil.

Frying oil is widely used in the food service.

Monitoring and managing Frying Oil is important to guarantee consistent high food quality. Furthermore, Frying Oil has an impact on the operation costs, especially since the prices of Frying Oil have increased significantly.

Frying is a traditional method for food preparation in the food service industry around the world. As frying process is carried on, frying oil degrades. The quality of the products from deep-fat frying depends not only on the product itself and the frying conditions, but also on the frying oil quality.

Not measuring frying oil quality frequently and regularly may cause operators to discard it prematurely or uses it beyond its quality limit point. That will cause money loss either by frying oil wastage or poor quality of the fried product.

Throughout the food service industry, there are several methods to determine frying oil quality discard point. Below are some common parameters used.

Frying oil color

It is a test based on the appearance of the frying oil to determine its discard point. In some cases, it is done by defining a visual point inside the frying vat where it can be seen through the frying oil. It can be either the heating components, the vat bottom, frying basket base or a metal rod with a disk on its base. If it is still possible to see it, the oil quality will be acceptable.

Another option is the color test kit. It consists of one small tube in between two color rods, one light color and the other one darker. Frying oil sample is poured in the center tube and compared with the 2 rods. Once the oil sample drawn matches the darker rod, it is time to discard the oil. It is a low-cost method, but one that is prone to operator interpretation.

Smoke

The test is based on human sensory perception. If smoke is coming out of the frying oil, it is beyond discard point. In extreme cases, there is a risk of the oil catching fire.

Oil rancidity and volatile compounds can be detected via smell, which may mean that the oil is beyond proper discard point. The method is quite inaccurate and can lead to discarding frying oil too late.

Free fatty acid measurement

The test measures free fatty acids (FFA), which is a frying oil quality parameter in some countries. It can be performed via test strips or with handheld devices. With test strips, they are dipped in the frying oil and then withdrawn. Frying oil FFA value is read comparing test strip against a color guide. The disadvantage of this method is the difficulty in interpretations and accuracy, the need to keep the strips under refrigeration and the cost per test. Handheld devices measure FFA based on dielectric constant calculation and are more accurate than test strips.

Total Polar Materials (TPM) measurement

Also known as total polar components (TPC) and is considered the chemical index of frying oil deterioration by measuring cumulative degradation products. The level of polar components is a good indicator of frying oil quality. Most countries around the world have legislation or recommendation regarding maximum percentage levels of polar components in frying oil. TPM values can be measured with handheld devices quickly and safely. Modern fryers already have a built in TPM measurement system.

If you want to learn more about the frying oil quality parameters and the test methods or other frying oil technical topics, please contact FILTROX.

GO TO THE FRYING OIL FILTRATION PAGE

Fried foods are popular all over the word. The frying oil or fat plays a very important role in the food service industry and has a direct impact on the food quality as well as in other aspects of the operation. This is about the about frying oils characteristics.

The Frying medium can be categorized as fat or oil. While oils are typically liquid at room temperature, fats retain a  solidconsistency at room temperature, like lard or tallow and some palm.

Choosing the right oil
There are many oils and fats available for frying in the market. The selection of frying media should be based on the optimization of the cooking process, with regards to nutritional facts, flavor profile, stability as well as costs involved.

From a health point of view, the frying oil or fat of choice should be rich in polyunsaturated fatty acids (linoleic and

linolenic acids). Unfortunately, oils and fats with that characteristic are too unstable for the harsh frying process. Also, oils with linolenic value higher than 3 % should be avoided as they may leave a fishy flavor within the food and the deep-frying medium.

To best fit nutritional and stability requirements, the fat and oil industry have been developing products that are low in saturated, linoleic and linolenic fatty acids and having at the same time higher amounts of the monounsaturated oleic acids. The downside of these oils are the higher price and lower availability when compared to regular products. To overcome it, edible oil manufactures have developed blends of different oils to balance cost, performance, availability and nutritional facts.

Below are the main types of oil and fats used in commercial frying.