Quality and longer shelf life of frying oil

In the meat industry, most fried products are breaded or coated. With these types of products, any problem with coating adhesion will become a potential risk of accelerating oil degradation, as the coating/coating particles and moisture from the product migrate into the oil, causing oxidation.

Due to the nature of the process, extending the shelf life of frying oils can be a challenge for processors, as the oils are sensitive to many factors involved in the frying process. Furthermore, oil oxidation is self-catalytic, so a small amount of oxidized oil can promote and accelerate the oxidation of fresh oil.

Types and quality of used oils

2018 is the year that, in the United States, processed foods must read zero trans fat on their nutrition label. The Food and Drug Administration (FDA) in that country gave the food industry three years to prepare for this deadline, but even before then researchers were already working on developing new oil blends and oil processing methods to obtain new oils that could serve replace partially hydrogenated fats, the main source of trans fats in processed foods.

One of the reasons why partially hydrogenated fats have been widely used is that the higher the amount of unsaturated fatty acids in the oil, the faster rancidity can occur. This means that oils considered healthier are less stable for storage and for applications involving high heat, such as frying. However, thanks to a large amount of research and development, you can now find quality oils that are also healthier and much more stable than their predecessors.

Today there are oils with a high content of monounsaturated fatty acids (MUFA) that can be used in high temperature processing and that show very good performance in frying operations. Several high oleic acid (omega 9) versions are available to processors, from non-genetically modified and organic sources of soybeans, canola, corn, sunflower seeds and safflower.

These new versions of vegetable oils are naturally stable and have a higher smoke point primarily because they have a unique fatty acid profile. Thus, these oils with a high content of omega 9 and a low content of polyunsaturated fatty acids have a longer shelf life and greater stability to heat and oxidation, because the need for synthetic antioxidants (TBHQ, BHT0) is eliminated, which makes these oils optimal for clean applications.

The downside of these oils is the price. They are more expensive than other budget mixes, and for some operations it is not always possible to pay a higher price. In the case of cheaper mixtures, the addition of antioxidants (synthetic or natural such as rosemary and sage) and anti-foaming agents is recommended. Some cheap oil blends are already sold with an anti-foaming agent built into them.

Frying temperature management

In most food processing facilities, a fryer is a unit operation performed by immersing food materials in hot oil (149-204°C/300-400°F) for complete or partial frying.

During the frying process, heat is transferred from hot oil to the surface of the food, while moisture is transferred from the interior of the product to the surface. At the same time, oxidation, polymerization and hydrolysis reactions take place in the food system and, depending on the temperature of the oil, the compounds resulting from these reactions contribute to the desirable or undesirable flavors of fried food.

Oil oxidizes faster at high temperatures, and even a small increase can speed up oxidation. For example, if the frying temperature is increased from 162°C to 176°C, the rate of the oxidation reaction more than doubles. Some of the high omega 9 oil blends can maintain stability and quality at 204°C.

In food service operations, frying is performed in oil at 162°C to 190°C. Most foods cook quickly in this temperature range and develop a golden brown color, crispy texture and good flavor.

Oils should not be preheated more than necessary. Very slow preheating is recommended to avoid local overheating of the surface. The product should be fried immediately after the oil reaches the desired temperature. Maintaining high temperatures for a long time without frying can increase oxidation. The frying process should be planned to avoid interruptions in production, especially if it is necessary to adjust the temperature between product batches to prevent overheating of the oil. The heat source of the equipment should be turned off immediately after the last batch of the day is finished to preserve the quality of the oil and the oil should be separated from the heat source as soon as possible before storage.

It’s worth investing in advanced temperature control. These computer controls constantly sense and adjust the temperature of the oil, keeping the temperature just a few degrees close to the programmed temperature, ensuring proper cooking and reducing the risks of rapid degradation.

Oil management for extended life

Moisture and particles from processed food and exposure to oxygen lead to numerous problems such as oxidation, polymerization, pyrolysis, sedimentation and hydrolysis of triglycerides that create undesirable odors and tastes, accumulation of free fatty acids, sticky dirt on equipment, accumulation of charred food particles that affect aroma, taste, color, foaming, reduced smoking points and reduced life of frying oil.

At the same time, the increase in oil viscosity results in an undesirable product texture and taste in the mouth, excessive fat absorption and reduced shelf life of the fried product. Then, as soon as the frying process is finished, the oil must be carefully cooled and transferred to a container in order to preserve its quality and extend its shelf life.

Oil filtration plays a major role in extending the life and maintaining the quality of frying oil. Today, most fryers have a built-in filtration system.

Filtering systems can be divided into passive and active, and until the mid-1980s almost all filtering systems were passive. Passive filtration is described as one in which suspended solids or particles are removed using screens or filters. Passive filtration can also be achieved by applying centrifugal force. An active filtration system is one in which not only these particles are removed, but also chemical components.

In active filtration, the filter contains embedded materials that trap compounds such as free fatty acids and oil oxidation byproducts. These compounds are chemically bound and removed from the oil. Another method of active oil filtration is the addition of adsorbents such as activated carbon. Some of the available activated carbon products (powder or granules) are optimized for the removal of specific compounds.

Frying oils must be filtered before storing in containers. Some operations may choose to add an external oil treatment system and remove all decomposition particles prior to storage. Depending on the type of operation and volume, this step is performed daily or weekly.

Source: Carnetec.

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