Application Cases | Use EPR Technology to Scientifically Evaluate the Quality of Edible Oil

From rich peanut oil to fragrant olive oil, various types of edible vegetable oils not only enrich people's food culture, but also meet diversified nutritional needs. With the improvement of the national economy and residents' living standards, the consumption of edible vegetable oils continues to grow, and it is particularly important to ensure its quality and safety.

1. Use EPR Technology to Scientifically Evaluate the Quality of Edible Oil

Electron paramagnetic resonance (EPR) technology, with its unique advantages (no pretreatment required, in-situ non-destructive, direct sensitivity), plays an important role in edible oil quality monitoring.

As a highly sensitive detection method, EPR can deeply explore the unpaired electron changes in the molecular structure of edible oils. These changes are often microscopic signs of the early stages of oil oxidation. The essence of oil oxidation is a free radical chain reaction. The free radicals in the oxidation process are mainly ROO·, RO· and R·.

By identifying oxidation products such as free radicals, EPR technology can scientifically evaluate the degree of oxidation and stability of edible oils before they show obvious sensory changes. This is essential to promptly detect and prevent grease deterioration caused by improper storage conditions such as light, heat, oxygen exposure or metal catalysis. Considering that unsaturated fatty acids are easily oxidized, edible oils face the risk of rapid oxidation even under normal temperature conditions, which not only affects their flavor and nutritional value, but also shortens the shelf life of the product.

Therefore, the use of EPR technology to scientifically evaluate the oxidation stability of oils can not only provide consumers with safer and fresher edible oil products, but also effectively guide the rational use of antioxidants, ensure the quality control of oil-containing foods, and extend the shelf life of market supply. . In summary, the application of electron paramagnetic resonance technology in the field of edible oil quality monitoring is not only a vivid manifestation of scientific and technological progress serving the people, but also an important line of defense for maintaining food safety and protecting public health.

2. Application cases of EPR in oil monitoring

Principle: A variety of free radicals will be generated during lipid oxidation. The generated free radicals are more active and have shorter lifespans. Therefore, the spin capture method is often used for detection (the spin capture agent reacts with the active free radicals to form a more stable Free radical adducts, PBN is generally used as a spin trap).

(1) Evaluate the oxidation stability of oil (the influence of external factors such as temperature on the oxidation stability of oil can be observed)

The antioxidant capacity of a product can be determined by measuring the concentration of free radicals and the gradual change in oxidation levels at each step of product manufacturing. The picture below shows the EPR spectrum of the free radical adduct formed by PBN capturing the free radicals generated by the oxidation of peanut oil. The degree of oxidation of the oil can be judged based on the EPR signal intensity. The stronger the EPR signal intensity, the greater the free radical content contained high.

Based on the EPR spectrum, the impact of different external conditions on oil oxidation, such as temperature, can also be obtained: As can be seen from the figure below, as the temperature increases, the intensity of the free radical EPR signal increases, indicating that the increase in temperature will accelerate the oil oxidation. 

(2) Evaluate the antioxidant capacity of different antioxidants (taking peanut oil as an example)

To compare the effects of different antioxidants on the EPR signal intensity of peanut oil, different antioxidants such as VE, BHT, BHA, BHA plus BHT and TBHQ plus CA were added to peanut oil. The effects of different antioxidants are shown in Figure 2B, and the Y-axis represents the amount of spin. As can be seen from this figure, the amount of spin in the sample with added antioxidants is significantly less than in the control group (peanut oil control, black line). Different antioxidants show different contributions to oil stability. The order of antioxidant effects is (TBHQ + CA) > (BHA + BHT) > BHA > BHT > VE. Among them, BHT+BHA showed better results than BHA or BHT respectively. TBHQ +CA works best. Because some metal ions (especially Cu²⁺ and Fe²⁺) can cause oxidation of oil. However, CA can be used as a chelating agent to chelate metal ions to further prevent oxidation.

(3) Oil Quality Monitoring-Identification of Adulteration in Waste Oil

Use old frying oil and refined bulk vegetable oil as raw materials, use PBN as the spin capture agent, and then use EPR to detect the changes in free radical intensity of the refined vegetable oil before and after adulteration, and use the spectrum fitting method to establish standards for free radical intensity and adulteration rate. Curve to quantify the adulteration ratio of waste oil in refined vegetable oil based on the standard curve. This method is highly sensitive and easy to operate, and can accurately identify adulterated vegetable oils with adulteration rates less than 20% and accurately quantify their adulteration rates.

3. Electron Paramagnetic Resonance (EPR) Spectroscopy

As the most direct and effective technology for detecting free radicals, electron paramagnetic resonance technology is of great significance in determining the degree of oxidation of food oils and fats and predicting their shelf life and shelf life. Electron Paramagnetic Resonance (EPR) Spectroscopy provides a non-destructive analysis method for directly detecting paramagnetic substances, which can quickly and accurately determine the antioxidant capacity of the product, thereby enabling informed process control. In addition, it can also provide information on the composition, structure, and dynamics of magnetic molecules, rare earth ions, ion clusters, doped materials, defective materials, metal proteins, and other substances containing unpaired electrons. In chemistry, biology, and physics, it has a wide range of applications in medicine, industry, and other fields.