Frying is one of the most commonly used methods of food processing, which is loved by consumers because of its unique flavor and taste. However, during the frying process, the oil is affected by high temperature, oxygen, moisture in the food and other factors, which will aggravate chemical reactions such as oxidation, hydrolysis, isomerization and polymerization, resulting in reduced oil stability, rapid deterioration in quality, and endangering human health. 

To retard oxidative deterioration, antioxidants are usually used. For safety reasons, synthetic antioxidants are increasingly being replaced by natural antioxidants. Rosemary extract comes from fresh rosemary leaves. It is one of the most popular natural antioxidants on the market due to its strong antioxidant capacity, good stability and relatively low price. Compounds in rosemary extract that exert strong antioxidant power include carnosic acid, carnosol, and rosmarinic acid, among others.

Studies have shown that rosemary extract can improve the oxidative stability of soybean oil during heating. The results of Guo et al. showed that 0.12 g/kg of rosemary ethanolic extract had a stronger protective effect on lipid peroxidation of palm oil during frying, compared with commonly used synthetic antioxidants. Cuevas et al. found that rosemary extract can effectively prevent the oxidation of rapeseed oil during storage and cooking. In 2010, the European Union officially approved rosemary extract as an antioxidant food additive, which can be used in frying oil.

In the experiment, first-grade soybean oil was used as raw material to continuously fry French fries, steamed bread and chicken wings at 180+5°C. The effect of soybean oil frying quality aims to provide a theoretical basis for the application of rosemary extract in the field of edible oils and fats, especially in the field of frying oil.