With the improvement of people's living standards in our country, consumers are paying more attention to the quality of edible oil. At the same time, the government is also vigorously promoting moderate refining and environmental protection. The oil and fat industry has also begun to pay attention to the moderate processing of edible oil, while ensuring high-quality products and preserving the original flavor and color of edible oil as much as possible. The refining of edible oil includes the main steps of degumming, deacidification, decolorization, deodorization, etc. The decolorization process directly affects consumers' judgment of the appearance quality of edible oil. If sunflower seed oil has a lighter color, some consumers may think that the quality of the oil is poor. In addition, moderate refining to maintain the color of fats is also a way to improve the quality of edible oils.

At present, the edible oil industry mainly uses adsorption decolorization method to decolorize edible oil, and the adsorbents used mainly include attapulgite, activated clay, activated carbon, etc. Attapulgite, activated clay, and activated carbon all have strong decolorization ability, which can effectively adsorb impurities in fats and oils, as well as pigments in edible oils, which may cause the color of edible oils to be too light. Silicon dioxide, as a new environmentally friendly adsorbent, has been widely used in the beer industry. It can effectively remove turbid proteins from beer without affecting the quality of beer products. Compared with other filter aids, silicon dioxide has the advantages of less addition and better effects. However, its application in the edible oil industry is relatively limited.

A rapidly developing and widely used silica material in materials science is porous silica, which is characterized by a large surface area, multiple pores, and large structural space. In addition, it also has properties such as low surface tension, low viscosity temperature coefficient, high compressibility, and high gas permeability. According to the pore size, porous silica materials can be divided into three categories: microporous silica materials with a diameter less than 2nm, mesoporous silica materials with a diameter between 2-50nm, and macroporous silica materials with a diameter greater than 50nm.

Before using new materials to replace old ones in production, it is necessary to conduct a thorough evaluation of their performance results. Using porous silica to adsorb and decolorize sunflower seed oil, the adsorption capacity of silica was investigated by measuring the color, phosphorus content, soap content, and oxidation induction period of the decolorized sunflower seed oil. At the same time, the adsorption effect of activated clay was compared, providing a reference for the application of silica in the decolorization of edible oil.

The effect of silica adsorption on the color of sunflower seed oil
Table 1 shows the effects of different amounts of silica and 0.5% activated clay on the color of sunflower seed oil.

From Table 1, it can be seen that the color of sunflower seed oil before decolorization has a yellow value of 70 and a red value of 3.5; By using silica adsorption for decolorization, the yellow value of sunflower seed oil decreases with the increase of silica addition, while the red value changes less. When the amount of silica added is 0.1%, the red and yellow values of sunflower seed oil are closest to those before decolorization; Comparing the same amount of silica added (0.5%) with activated clay, it was found that the adsorption and decolorization effect of silica was weaker than that of activated clay, indicating that the use of silica in the experiment can improve the problem of too light color of sunflower seed oil.

The adsorption capacity of silica for impurities in sunflower seed oil
Table 2 shows the adsorption effects of different amounts of silica and 0.5% activated clay on soap and phosphorus in sunflower seed oil.

From Table 2, it can be seen that the soap content and phosphorus content in sunflower seed oil after adsorption decolorization with different amounts of silica were not detected, while the soap content in sunflower seed oil after adsorption decolorization with 0.5% activated clay was 3.0mg/kg, indicating that silica has better adsorption capacity for soap and phosphorus than activated clay. When the amount of silicon dioxide added is 0.1%, both the soap content and phosphorus content have not been detected, indicating that a low amount of silicon dioxide (0.1%) can achieve a more significant adsorption effect than a high amount of activated clay (0.5%). If applied in industrial production, it can effectively save production costs.

The effect of silica on the oxidative stability of sunflower seed oil
Figure 1 shows the effect of different amounts of silica and 0.5% active clay on the oxidative induction period of sunflower seed oil.

From Figure 1, it can be seen that with the increase of silicon dioxide addition, the oxidation stability of sunflower seed oil does not change much and is better than that of 0.5% active clay. This may be due to the hydrolysis of some oils during the adsorption process of activated clay, resulting in an increase in the acidity of the oils and a decrease in the oxidation induction period. In summary, the oxidation stability of sunflower seed oil treated with silica is better, and its application in industry can also reduce its dosage and save costs.
conclusion

In response to the problem of shallow oil color caused by conventional oil decolorization methods, using activated clay as a comparison, silica was used to adsorb and decolorize sunflower seed oil. The relevant indicators of sunflower seed oil after adsorption were measured. The results showed that when the amount of silica added was 0.1%, its effect on the soap content and phosphorus content in sunflower seed oil could reach or even be better than that of 0.5% activated clay adsorption decolorization. At the same time, it could maintain the color before decolorization to the greatest extent possible, and the oxidation stability of sunflower seed oil was improved. Adding less silica can yield better quality sunflower seed oil while significantly reducing the use of active clay, which can help businesses save production costs.

The color index of the oil in this experiment was measured by a colorimeter, and the impurity test of the oil was carried out in accordance with GB5009.87-2016 "National Food Safety Standard - Determination of Phosphorus in Food" and GB/T5533-2008 "Inspection of Grain and Oil - Determination of Soap Content in Plant Oils". The oxidative stability of fats and oils is measured using the OXITEST method.

The OXITEST method is tested using the OXITEST lipid oxidation analyzer, which evaluates the resistance of the sample to lipid oxidation in a short period of time by placing it in a high oxidative stress environment. 

The results of OXITEST are represented by the IP induction period. IP refers to the time required to reach the oxidation starting point, corresponding to the detectable degree of rancidity or sudden changes in oxidation rate. The longer the induction period, the higher the stability of antioxidant activity. Further analyze the stability of the sample or evaluate its shelf life.